ISSN Exercise & Sport Nutrition Review: Research & Recommendations

Sport nutrition is a constantly evolving field with literally thousands of research papers published annually. For this reason, keeping up to date with the literature is often difficult. This paper presents a well-referenced overview of the current state of the science related to how to optimize training through nutrition. More specifically, this article discusses: 1.) how to evaluate the scientific merit of nutritional supplements; 2.) general nutritional strategies to optimize performance and enhance recovery; and, 3.) our current understanding of the available science behind weight gain, weight loss, and performance enhancement supplements. Our hope is that ISSN members find this review useful in their daily practice and consultation with their clients.


INTRODUCTION
Sport nutrition professionals need to know how to evaluate the scientific merit of articles and advertisements about exercise and nutrition products so they can separate marketing hype from scientifically based training and nutritional practices. In order to help educate ISSN members about sport nutrition, we have updated a letter to the Editor (PEP Online. 6 (10), 2003) which represents a compilation of Dr. Kreider's published work in this area for the Sport Nutrition Review Journal's inaugural issue. This paper provides an overview of: 1.) what are ergogenic aids and dietary supplements; 2.) how dietary supplements are legally regulated; 3.) how to evaluate the scientific merit of nutritional supplements; 4.) general nutritional strategies to optimize performance and enhance recovery; and, 5.) an overview of our current understanding of the ergogenic value weight gain, weight loss, and performance enhancement supplements. We have also categorized nutritional supplements into apparently effective, possibly effective, too early to tell, and apparently ineffective as well as describes our general approach to educating athletes about sport nutrition. While some may not agree with all of our interpretations of the literature and/or categorization of a particular supplement and some classifications may change over time as more research is forthcoming, these interpretations are based on the current available scientific evidence and have been well received within the broader scientific community. Our hope is that ISSN members find this information useful in their daily practice and consultation with their clients.

WHAT IS AN ERGOGENIC AID?
An ergogenic aid is any training technique, mechanical device, nutritional practice, pharmacological method, or psychological technique that can improve exercise performance capacity and/or enhance training adaptations 1,2 . This includes aids that may help prepare an individual to exercise, improve the efficiency of exercise, and/or enhance recovery from exercise. Ergogenic aids may also allow an individual to tolerate heavy training to a greater degree by helping them recover faster or help them stay healthy during intense training. Although this definition seems rather straightforward, there is considerable debate regarding the ergogenic value of various nutritional supplements. Some sport nutrition specialists only consider a supplement ergogenic if studies show that the supplement significantly enhances exercise performance (e.g., helps you run faster, lift more weight, and/or perform more work during a given exercise task). On the other hand, some feel that if a supplement helps prepare an athlete to perform or enhances recovery from exercise, it has the potential to improve training adaptations and therefore should be considered ergogenic. In our view, one should take a broader view about the ergogenic value of supplements. While we are interested in determining the performance enhancement effects of a supplement on a single bout of exercise, we also realize that one of the goals of training is to help people tolerate training to a greater degree. People who tolerate training better usually experience greater gains from training over time. Consequently, employing nutritional practices that help prepare people to perform and/or enhance recovery from exercise should also be viewed as ergogenic.

WHAT ARE DIETARY SUPPLEMENTS AND HOW ARE THEY REGULATED?
According to the Food and Drug Administration (FDA), dietary supplements were regulated in the same manner as food prior to 1994 3 . Consequently, the manufacturing processes, quality, and labeling of supplements were monitored by FDA. However, many people felt that the FDA was too restrictive in regulating dietary supplements. As a result, Congress passed the Dietary Supplement Health and Education Act (DSHEA) in 1994 which placed dietary supplements in a special category of "foods". In October 1994, DSHEA was signed into law by President Clinton. The law defined a "dietary supplement" as a product taken by mouth that contains a "dietary ingredient" intended to supplement the diet. "Dietary ingredients" may include vitamins, minerals, herbs or other botanicals, amino acids, and substances (e.g., enzymes, organ tissues, glandulars, and metabolites). Dietary supplements may also be extracts or concentrates from plants or foods. Dietary supplements are typically sold in the form of tablets, capsules, soft gels, liquids, powders, and bars. Products sold as dietary supplements must be clearly labeled as a dietary supplement.
According to DSHEA, dietary supplements are not drugs. Dietary supplement ingredients that were sold prior to 1994 are therefore not required to be shown to be safe and/or effective in clinical trials prior to being approved for sale by the FDA. However, new dietary supplement ingredients introduced after 1994 must undergo pre-market review for safety data by the FDA before it can be legally sold. Supplement companies are responsible for determining that the dietary supplements it manufactures or distributes are safe and that any representations or claims made about them are substantiated by adequate evidence to show that they are not false or misleading. Because of this, DSHEA requires supplement manufacturers to include on the label that "This statement has not been evaluated by the FDA. This product is not intended to diagnose, treat, cure, or prevent any disease". According to the 1994 Nutrition Labeling and Education Act (NELA), the FDA has the ability to review and approve health claims for dietary supplements and foods. However, since the law was passed, it has only reviewed a few claims. The delay in reviewing health claims of dietary supplements resulted in a law suit filed by Pearson & Shaw et al v. Shalala et al in 1993. After years of litigation, U.S. Court of Appeals for the District of Columbia Circuit ruled in 1999 that qualified health claims may now be made about dietary supplements with approval by FDA as long as the statements are truthful and based on science. Supplement companies wishing to make health claims about supplements can submit research evidence to the FDA for approval. Additionally, they must submit an Investigation of New Drug (IND) application to FDA if a research study on a nutrient is designed to treat an illness and/or medical affliction and/or the company hopes to one day obtain approval for making a qualified health claim if the outcome of the study supports the claim. Studies investigating structure and function claims, however, do not need to be submitted to the FDA as an IND.
Manufacturers and distributors of dietary supplements are not currently required to record, investigate or forward to FDA any reports they receive on injuries or illnesses that may be related to the use of their products. However, the FDA and other groups have established phone hotlines and online adverse event monitoring systems to report problems they believe may be a result of taking dietary supplements. While these reports are unsubstantiated, can be influenced by media attention to a particular supplement, and do not necessarily show a cause and effect, they are used by the FDA to monitor trends and "signals" that may suggest a problem. Once a dietary supplement product is marketed, the FDA has the responsibility for showing that a dietary supplement is unsafe before it can take action to restrict the product's use or removal from the marketplace. The Federal Trade Commission (FTC) is responsible to make sure manufacturers are truthful regarding claims they make about dietary supplements. The FDA has the power to remove supplements from the market if it has sufficient scientific evidence to show the supplement is unsafe. Additionally, the FTC has the power to act against companies who make false and/or misleading marketing claims about a specific product. This includes acting against companies if the ingredients found in the supplement do not match label claims. While this does not ensure the safety of dietary supplements, it does provide a means for governmental oversight of the dietary supplement industry if adequate resources are provided to enforce DSHEA. Since inception of DSHEA, the FDA has required a number of supplement companies to submit evidence showing safety of their products and acted to remove a number of products sold as dietary supplements from sale in the U.S. due to safety concerns. Additionally, the FTC has acted against a number of supplement companies for misleading advertisements and/or structure and function claims.
As can be seen, although some argue that the dietary supplement industry is "unregulated" and/or may have suggestions for additional regulation, manufacturers of dietary supplements must adhere to a number of federal regulations before a product can go to market. Further, they must have evidence that the ingredients sold in their supplements are generally safe if requested to do so by the FDA. For this reason, over the last [10][11][12][13][14][15] years, most quality supplement companies have employed a team of researchers (many of whom are MS or PhD prepared exercise physiologists or sport nutrition specialists) who help educate the public about nutrition and exercise, provide input on product development, conduct preliminary research on products, and/or assist in coordinating research trials conducted by independent research teams (e.g., university based researchers or clinical research sites). They also consult with marketing teams with the responsibility to ensure structure and function claims do not misrepresent results of research findings. This has increased job opportunities for sport nutrition specialists as well as enhanced opportunities for external funding for research groups interested in exercise nutrition research. While it is true that some companies use borrowed science, suppress negative findings, and/or exaggerate results from research studies, the trend in the nutrition industry is to develop scientifically sound supplements. This trend toward greater research support is the result of: 1.) attempts to honestly and accurately inform the public about results; 2.) efforts to have data to support safety and efficacy on products for FDA and the FTC; and/or, 3.) to provide scientific evidence to support advertising claims and increase sales. This trend is due in large part to greater scrutiny from the FDA and FTC as a result of increased consumer expectations and political pressure to ensure that companies sell quality products that have been shown to be safe and effective in clinical trials. In our experience, companies who adhere to these ethical standards prosper while those who do not struggle to adhere to FDA and FTC guidelines and lose consumer confidence. When this occurs, companies are often sued by consumers and/or are forced out of business because ultimately the consumer has the final word on whether a supplement or supplement company is credible or not.

HOW TO EVALUATE NUTRITIONAL ERGOGENIC AIDS
When you evaluate the ergogenic value of a nutritional supplement or training device/method, we recommend that you go through a process of evaluating the validity and scientific merit of claims made. This can be accomplished by evaluating the theoretical rationale behind the supplement/technique and determining whether there is any wellcontrolled data showing the supplement/technique works. Training devices and supplements based on sound scientific rationale with supportive research showing effectiveness may be worth trying and/or recommending. However, those based on unsound scientific rationales and/or little to no data supporting the ergogenic value for people involved in intense training may not. The sport nutrition specialist should be a resource to help their clients interpret the scientific and medical research that may impact on their welfare and/or help them train more wisely. The following are the questions we recommend asking when evaluating the potential ergogenic value of a supplement.

Does The Theory Make Sense?
Most supplements that have been marketed to improve health and/or exercise performance are based on theoretical applications derived from basic and/or clinical research studies. Based on these preliminary studies, a training device or supplement is often marketed to people proclaiming the benefits observed in these basic research studies. Although the theory may sound good, critical analysis of the theory often reveals flaws in scientific logic and/or that the claims made don't quite match up with the literature cited. If you do your homework, you can discern whether a supplement has been based on sound scientific evidence or not. To do so, we suggest you read reviews about the training method, nutrient, and/or supplement from researchers who have been intimately involved in this line of research and/or consult reliable references about nutritional and herbal supplements [4][5][6][7][8] . We also suggest doing a search on the nutrient/supplement on the National Library of Medicine's Pub Med Online 9 . A quick look at these references will often help you know whether the theory is plausible or not. In our experience, proponents of ergogenic aids often overstate claims made about training devices and/or nutritional supplements while opponents of nutritional supplements and ergogenic aids are either unaware and/or ignorant of research supporting their use. The sport nutrition specialist has the responsibility to know the literature and/or search available data bases to know whether there is merit or not to a proposed ergogenic aid.

Is There Any Scientific Evidence Supporting The Ergogenic Value?
The next question suggest asking is whether there is any well-controlled data showing the proposed ergogenic aid works as claimed in athletes or people involved in training. The first place we look is the list of references cited in marketing material supporting their claims. We look to see if the abstracts or articles cited are general references or specific studies that have evaluated the efficacy of the nutrient/supplement. We then critically evaluate the abstracts and articles by asking a series of questions.
Are the studies simply basic research done in animals/clinical populations or have the studies been conducted on athletes? Studies reporting improved performance in rats may be insightful but research conducted on athletes is much more convincing.
Were the studies well controlled? For ergogenic aid research, the study should be a placebo controlled, double blind, and randomized clinical trail if possible. This means that neither the researcher's nor the subject's were aware which group received the supplement or the placebo during the study and that the subjects were randomly assigned into the placebo or supplement group. At times, supplement claims have been based on poorly designed studies (i.e., small groups of subjects, no control group, use of unreliable tests, etc) and/or testimonials which may make interpretation much more difficult. Studies that are well controlled clinical trials provide stronger evidence as to the potential ergogenic value than those that are not well controlled.
Do the studies report statistically significant results or are claims being made on non-significant means or trends reported? Appropriate statistical analysis of research results allows for an unbiased interpretation of data. Although studies reporting statistical trends may be of interest and lead researchers to conduct additional research, studies reporting statistically significant results are obviously more convincing. With this said, sport nutrition specialist must be careful not to commit type II statistical error (i.e., indicating that no differences were observed when a true effect was seen but not detected statistically). Since many studies on ergogenic aids (particularly in high level athletes) evaluate small numbers of subjects, results may not reach statistical significance even though large mean changes were observed. In these cases, additional research is warranted to further examine the potential ergogenic aid before conclusions can be made. Do the results of the studies cited match the claims made about the supplement? It is not unusual for marketing claims to greatly exaggerate the results found in the actual studies. Therefore, you should compare results observed in the studies to marketing claims. Reputable companies accurately report results of studies so that consumers can make informed decisions about whether to try a product or not. Were results of the study presented at a reputable scientific meeting and/or published in a peer-reviewed scientific journal? At times, claims are based on research that has either never been published or only published in an obscure journal. The best research is typically presented at respected scientific meetings and/or published in reputable peerreviewed journals. Have the research findings been replicated at several different labs? The best way to know an ergogenic aid works is to see that results have been replicated in several studies preferably by a number of researchers. The most reliable ergogenic aids are those in which a number of studies, conducted at different labs, have reported similar results.

Is The Supplement Legal And Safe?
The final question we ask is whether the supplement is legal and/or safe. Some athletic associations have banned the use of various nutritional supplements (e.g., prohormones, ephedra, etc). Obviously, if the supplement is banned, the sport nutrition specialist should discourage its use. In addition, many supplements have not been studied for long-term safety. People who consider taking nutritional supplements should be well aware of the potential side effects so that they can make an informed decision regarding whether to use a supplement or not. Additionally, they should consult with a knowledgeable physician to see if there are any underlying medical problems that may contraindicate use. When evaluating the safety of a supplement, we suggest looking to see if any side effects have been reported in the scientific or medical literature. In particular, we suggest determining how long a particular supplement has been studied, the dosages evaluated, and whether any side effects were observed. We also recommend consulting the PDR for nutritional supplements and herbal supplements to see if any side effects have been reported and/or there are any known drug interactions. If no side effects have been reported in the scientific/medical literature, we generally will view the supplement as safe for the length of time and dosages evaluated.

CLASSIFYING AND CATEGORIZING SUPPLEMENTS
Dietary supplements may contain carbohydrate, protein, fat, minerals, vitamins, herbs, and/or various plant/food extracts. Supplements can generally be classified as convenience supplements (e.g., energy bars, meal replacement powders, ready to drink supplements) designed to provide a convenient means of meeting caloric needs and/or managing caloric intake, weight gain supplements, weight loss supplements, and performance enhancement supplements. Based on the above criteria, we generally categorize nutritional supplements into the following categories: I. Apparently Effective. Supplements that help people meet general caloric needs and/or the majority of research studies show is effective and safe. II. Possibly Effective. Supplements that initial studies support the theoretical rationale but that more research is needed to determine how the supplement may affect training and/or performance. III. Too Early To Tell. Supplements that the theory may make sense but there is insufficient research to support the use at this time. IV. Apparently Ineffective. Supplements that the theoretical rationale makes little scientific sense and/or research has clearly shown to be ineffective.
When a sport nutrition specialist councils people who train, they should first evaluate their diet and training program. They should make sure that the athlete is eating an energy balanced, nutrient dense diet and that they are training intelligently. This is the foundation to build a good program. Following this, we recommend that they generally only recommend supplements in category I. If someone is interested in trying supplements in category II, they should make sure that they understand that these supplements are more experimental and that they may or may not see the type of results claimed. We recommend discouraging people from trying supplements in category III because there isn't enough data available on whether they work or not. However, if someone wants to try one of these supplements, they should understand that although there is some theoretical rationale, there is little evidence to support use at this time. Obviously, we do not support athletes taking supplements in categories IV. We believe that this approach is a more scientifically supportable and balanced view than simply dismissing the use of all dietary supplements out of hand.

GENERAL DIETARY GUIDELINES FOR ACTIVE INDIVIDUALS
A well-designed diet that meets energy intake needs and incorporates proper timing of nutrients is the foundation upon which a good training program can be developed. Research has clearly shown that athletes that do not ingest enough calories and/or do not consume enough of the right type of macronutrients may impede training adaptations while athletes who consume a good diet can help the body adapt to training. Moreover, maintaining an energy deficient diet during training may lead to loss of muscle mass, increased susceptibility to illness, and increase prevalence of overreaching and/or overtraining. Incorporating good dietary practices as part of a training program is one way to help optimize training adaptations and prevent overtraining. The following overviews energy intake and major nutrient needs of active individuals.

Energy Intake
The first component to optimize training and performance through nutrition is to ensure the athlete is consuming enough calories to offset energy expenditure 1, 10-12 . People who participate in a general fitness program (e.g., exercising 30 -40 minutes per day, 3 times per week) can generally meet nutritional needs following a normal diet (e.  [13][14][15] . Additionally, caloric needs for large athletes (i.e., 100 -150 kg) may range between 6,000 -12,000 kcals/day depending on the volume and intensity of different training phases 13 .
Although some argue that athletes can meet caloric needs simply by consuming a wellbalanced diet, it is often very difficult for larger athletes and/or athletes engaged in high volume/intense training to be able to eat enough food in order to meet caloric needs 1,11,[13][14][15] . Maintaining an energy deficient diet during training often leads to significant weight loss (including muscle mass), illness, onset of physical and psychological symptoms of overtraining, and reductions in performance 12 . Nutritional analyses of athletes' diets have revealed that many are susceptible to maintaining negative energy intakes during training. Susceptible populations include runners, cyclists, swimmers, triathletes, gymnasts, skaters, dancers, wrestlers, boxers, and athletes attempting to lose weight too quickly 11 . Additionally, female athletes have been reported to have a high incidence of eating disorders 11 . Consequently, it is important for the sport nutrition specialist working with athletes to ensure that athletes are well-fed and consume enough calories to offset the increased energy demands of training and maintain body weight. Although this sounds relatively simple, intense training often suppresses appetite and/or alters hunger patterns so that many athletes do not feel like eating 11 . Some athletes do not like to exercise within several hours after eating because of sensations of fullness and/or a predisposition to cause gastrointestinal distress. Further, travel and training schedules may limit food availability and/or the types of food athletes are accustomed to eating. This means that care should be taken to plan meal times in concert with training as well as make sure athletes have sufficient availability of nutrient dense foods throughout the day for snacking between meals (e.g., drinks, fruit, carbohydrate/protein bars, etc) 1,10,11 . For this reason, sport nutritionists' often recommend that athletes consume 4-6 meals per day and snack in between meals in order to meet energy needs. Use of nutrient dense energy bars and high calorie carbohydrate/protein supplements provides a convenient way for athletes to supplement their diet in order to maintain energy intake during training.

Carbohydrate
The

Protein
There has been considerable debate regarding protein needs of athletes [16][17][18][19][20] . Initially, it was recommended that athletes do not need to ingest more than the RDA for protein (i.e., 0.8 to 1.0 g/kg/d for children, adolescents and adults). However, research over the last decade has indicated that athletes engaged in intense training need to ingest about 1.5 -2 times the RDA of protein in their diet (1.5 to 2.0 g/kg/d) in order to maintain protein balance [16][17][18][19][20] . If an insufficient amount of protein is obtained from the diet, an athlete will maintain a negative nitrogen balance which can increase protein catabolism and slow recovery. Over time, this may lead to lean muscle wasting and training intolerance 1, 12 .
For people involved in a general fitness program, protein needs can generally be met by ingesting 0. However, it should be noted that not all protein is the same. Proteins differ based on the source that the protein was obtained, the amino acid profile of the protein, and the methods of processing or isolating the protein 22 . These differences influence availability of amino acids and peptides that have been reported to possess biological activity (e.g., α-lactalbumin, ßlactoglobulin, glycomacropeptides, immunoglobulins, lactoperoxidases, lactoferrin, etc). Additionally, the rate and metabolic activity of the protein 22 . For example, different types of proteins (e.g., casein and whey) are digested at different rates which directly affect catabolism and anabolism [22][23][24][25] . Therefore, care should be taken not only to make sure the athlete consumes enough protein in their diet but also that the protein is high quality. The best dietary sources of low fat and high quality protein are light skinless chicken, fish, egg white and skim milk (casein and whey) 22 . The best sources of high quality protein found in nutritional supplements is whey, colostrum, casein, milk proteins and egg protein 21,22 . Although some athletes may not need to supplement their diet with protein and some sport nutrition specialists may not think that protein supplements are necessary, suggestions that it is unethical for an sport nutrition specialist to recommend that some athletes supplement their diet with protein in order to meet dietary protein needs and/or provide essential amino acids following exercise in order to optimize protein synthesis is clearly not supported by the literature.

Fat
The dietary recommendations of fat intake for athletes are similar to or slightly greater than those recommended for non-athletes in order to promote health. Maintenance of energy balance, replenishment of intramuscular triacylglycerol stores and adequate consumption of essential fatty acids are of greater importance among athletes and allow for somewhat increased intake 26 . This depends on the athlete's training state and goals. For example, higher-fat diets appear to maintain circulating testosterone concentrations better than low-fat diets [27][28][29] . This has relevance to the documented testosterone suppression which can occur during volume-type overtraining 30 . Generally, it is recommended that athletes consume a moderate amount of fat (approximately 30% of their daily caloric intake), while increases up to 50% of kcal can be safely ingested by athletes during regular high-volume training 26 . For athletes attempting to decrease body fat, however, it has been recommended that they consume 0.5 to 1 g/kg/d of fat 1 . The reason for this is that some weight loss studies indicate that people who are most successful in losing weight and maintaining the weight loss are those who ingest less than 40 g/d of fat in their diet 31, 32 although this is not always the case 33 . Certainly, the type of dietary fat (e.g. n-6 versus n-3; saturation state) is a factor in such research and could play an important role in any discrepancies 34,35 . Strategies to help athletes manage dietary fat intake include teaching them which foods contain various types of fat so that they can make better food choices and how to how to count fat grams 1,11 .

Strategic Eating and Refueling
In addition to the general nutritional guidelines described above, research has also demonstrated that timing and composition of meals consumed may play a role in optimizing performance, training adaptations, and preventing overtraining 1,10,36,37 . In this regard, it takes about 4 hours for carbohydrate to be digested and begin to be stored as muscle and liver glycogen. Consequently, pre-exercise meals should be consumed about 4 to 6 h before exercise 10 . This means that if an athlete trains in the afternoon, breakfast is the most important meal to top off muscle and liver glycogen levels. Research has also indicated that ingesting a light carbohydrate and protein snack 30 to 60 min prior to exercise (e.g., 50 g of carbohydrate and 5 to 10 g of protein) serves to increase carbohydrate availability toward the end of an intense exercise bout 38,39 . This also serves to increase availability of amino acids and decrease exercise-induced catabolism of protein 36,38,39 .
When exercise lasts more than one hour, athletes should ingest glucose/electrolyte solution (GES) drinks in order to maintain blood glucose levels, help prevent dehydration, and reduce the immunosuppressive effects of intense exercise 10, 40-45 . Following intense exercise, athletes should consume carbohydrate and protein (e.g., 1 g/kg of carbohydrate and 0.5 g/kg of protein) within 30 min after exercise as well as consume a high carbohydrate meal within two hours following exercise 1,36,37 . This nutritional strategy has been found to accelerate glycogen resynthesis as well as promote a more anabolic hormonal profile that may hasten recovery [46][47][48]  Medical Association also recently evaluated the available medical literature and recommended that Americans consume a onea-day low-dose multivitamin in order to promote general health. Suggestions that there is no benefit of vitamin supplementation for athletes and/or it is unethical for an sport nutrition specialist to recommend that their clients take a one-a-day multi-vitamin and/or suggest taking other vitamins that may reduce cholesterol levels (niacin), serve as antioxidants (Vitamin E), decrease risk to heart disease (niacin, Vitamin E), or may help maintain a health immune system (Vitamin C) is not consistent with current available literature.

Minerals
Minerals are essential inorganic elements necessary for a host of metabolic processes. Minerals serve as structure for tissue, important components of enzymes and hormones, and regulators of metabolic and neural control. Some minerals have been found to be deficient in athletes or become deficient in response to training and/or prolonged exercise. When mineral status is inadequate, exercise capacity may be reduced. Dietary supplementation of minerals in deficient athletes has generally been found to improve exercise capacity. Additionally, supplementation of specific minerals in nondeficient athletes has also been reported to affect exercise capacity. Table 2 describes minerals that have been purported to affect exercise capacity in athletes. Of the minerals reviewed, several appear to possess health and/or ergogenic value for athletes under certain conditions. For example, calcium supplementation in athletes susceptible to premature osteoporosis may help maintain bone mass. There is also recent evidence that dietary calcium may help manage body composition. Iron supplementation in athletes prone to iron deficiencies and/or anemia has been reported to improve exercise capacity. Sodium phosphate loading has been reported to increase maximal oxygen uptake, anaerobic threshold, and improve endurance exercise capacity by 8 to 10%. Increasing dietary availability of salt (sodium chloride) during the initial days of exercise training in the heat has been reported to help maintain fluid balance and prevent dehydration. Finally, zinc supplementation during training has been reported to decrease exercise-induced changes in immune function. Consequently, somewhat in contrast to vitamins, there appear to be several minerals that may enhance exercise capacity and/or training adaptations for athletes under certain conditions. However, although ergogenic value has been purported for remaining minerals, there is little evidence that boron, chromium, magnesium, or vanadium affect exercise capacity or training adaptations in healthy individuals eating a normal diet.
Suggestions that there is no benefit of mineral supplementation for athletes and/or it is unethical for an sport nutrition specialist to recommend that their clients take minerals that research has shown may affect health and/or performance is not consistent with current available literature.

Water
The most important nutritional ergogenic aid for athletes is water. Exercise performance can be significantly impaired when 2% or more of body weight is lost through sweat. For example, when a 70-kg athlete loses more than 1.4 kg of body weight during exercise (2%), performance capacity is often significantly decreased. Further, weight loss of more than 4% of body weight during exercise may lead to heat illness, heat exhaustion, heat stroke, and possibly death 45 . For this reason, it is critical that athletes consume a sufficient amount of water and/or GES sports drinks during exercise in order to maintain hydration status. The normal sweat rate of athletes ranges from 0.5 to 2.0 L/h depending on temperature, humidity, exercise intensity, and their sweat response to exercise 45 . This means that in order to maintain fluid balance and prevent dehydration, athletes need to ingest 0.5 to 2 L/h of fluid in order to offset weight loss. This requires frequent ingestion of 6-8 oz of cold water or a GES sports drink every 5 to 15-min during exercise 45,[49][50][51][52] . Athletes and should not depend on thirst to prompt them to drink because people do not typically get thirsty until they have lost a significant amount of fluid through sweat. Additionally, athletes should weigh themselves prior to and following exercise training to ensure that they maintain proper hydration 45,[49][50][51][52] . The athlete should consume 3 cups of water for every pound lost during exercise in order adequately rehydrate themselves 45 . Athletes should train themselves to tolerate drinking greater amounts of water during training and make sure that they consume more fluid in hotter/humid environments. Preventing dehydration during exercise is one of the most effective ways to maintain exercise capacity. Finally, inappropriate and excessive weight loss techniques (e.g., cutting weight in saunas, wearing rubber suits, severe dieting, vomiting, using diuretics, etc) are extremely dangerous and should be prohibited. Sport nutrition specialists can play an important role in educating athletes and coaches about proper hydration methods and supervising fluid intake during training and competition.

DIETARY SUPPLEMENTS AND ATHLETES
Most of the work we do with athletes regarding sport nutrition is to teach them and their coaches how to structure their diet and time food intake to optimize performance and recovery. Dietary supplements can play a meaningful role in helping athletes consume the proper amount of calories, carbohydrate, and protein in their diet. However, they should be viewed as supplements to the diet, not replacements for a good diet. While it is true that most dietary supplements available for athletes have little scientific data supporting their potential role to enhance training and/or performance, it is also true that a number of nutrients and/or dietary supplements have been shown to help improve performance and/or recovery. This can help augment the normal diet to help optimize performance. Sport nutrition specialists must be aware of the current data regarding nutrition, exercise, and performance and be honest about educating their clients about results of various studies (whether pro or con). With the proliferation of information available about nutritional supplements to the consumer, the sport nutrition specialist, nutritionist, and nutrition industry lose credibility when they do not accurately describe results of various studies to the public. The following overviews several classifications of nutritional supplements that are often taken by athletes and categorizes them into apparently effective, possibly effective, too early to tell, and apparently ineffective supplements based on my interpretation of the literature. It should be noted that this analysis will primarily focus on whether the proposed nutrient has been found to affect exercise and/or training adaptations based on the current available literature. Additional research may reveal it may or may not possess ergogenic value which may then change its classification. It should be also noted that although there may be little ergogenic value to some nutrients, there may be some potential health benefits that may be helpful for some populations. Therefore, just because a nutrient does not appear to affect performance and/or training adaptations, that does not mean it may not have possible health benefits.

Convenience Supplements
Convenience supplements are meal replacement powders (MRP's), ready to drink supplements (RTD's), energy bars, and energy gels. They currently represent the largest segment of nutrition industry representing 50 -75% of most company's sales. They are typically fortified with 33 -50% of the RDA for vitamins and minerals and typically differ on the amount of carbohydrate, protein, and fat they contain. They may also differ based whether they are fortified with various nutrients purported to promote weight gain, enhance weight loss, and/or improve performance. Most people view these supplements as a high quality snacks and/or use them to help control caloric intake when trying to gain and/or lose weight. In our view, MRP's, RTD's, and energy bars/gels can provide a convenient way for people to meet specific dietary needs and/or serve as good alternatives to fast food. Use of these types of products can be particularly helpful in providing carbohydrate, protein, and other nutrients prior to and/or following exercise in an attempt to optimize nutrient intake when an athlete doesn't have time to sit down for a good meal. However, they should be used to improve dietary availability of macronutrients -not as a replacement for a good diet. Care should also be taken to make sure they do not contain any banned or prohibited nutrients.

Muscle Building Supplements
The following provides an analysis of the literature regarding purported weight gain supplements and our general interpretation of how they should be categorized based on this information. Table 3 summarizes how we currently classify the ergogenic value of a number of purported performance-enhancing, muscle building, and fat loss supplements based on an analysis of the available scientific evidence.

Apparently Effective
Weight Gain Powders. One of the most common means athletes have employed to increase muscle mass is to add extra calories to the diet. Most athletes "bulk up" in this manner by consuming extra food and/or weight gain powders. Studies have consistently shown that simply adding an extra 500 -1,000 calories per day to your diet will promote weight gain 20,36 . However, only about 30 -50% of the weight gained on high calorie diets is muscle while the remaining amount of weight gained is fat. Consequently, increasing muscle mass by ingesting a high calorie can help you build muscle but the accompanying increase in body fat may not be desirable for everyone.
Therefore, we typically do not recommend this type of weight gain approach.
Creatine. In our view, the most effective nutritional supplement available to athletes to increase high intensity exercise capacity and muscle mass during training is creatine. Numerous studies have indicated that creatine supplementation increases body mass and/or muscle mass during training 53 Gains are typically 2 -5 pounds greater than controls during 4 -12 weeks of training 54 . The gains in muscle mass appear to be a result of an improved ability to perform high intensity exercise enabling an athlete to train harder and thereby promote greater training adaptations and muscle hypertrophy [55][56][57] . The only clinically significant side effect reported from creatine supplementation has been weight gain 36,53,54,58 Although concerns have been raised about the safety and possible side effects of creatine supplementation 59, 60 , recent long-term safety studies have reported no apparent side effects 58,61,62 and/or that creatine may lessen the incidence of injury during training [63][64][65] . Consequently, supplementing the diet with creatine and/or creatine containing formulations seems to be a safe and effective method to increase muscle mass.
β-hydroxy β-methylbutyrate (HMB). HMB is a metabolite of the amino acid leucine. Leucine and metabolites of leucine have been reported to inhibit protein degradation 66 . Supplementing the diet with 1.5 to 3 g/d of calcium HMB has been typically reported to increase muscle mass and strength particularly among untrained subjects initiating training [67][68][69][70][71][72] and the elderly 73 . Gains in muscle mass are typically 0.5 to 1 kg greater than controls during 3 -6 weeks of training. There is also recent evidence that HMB may lessen the catabolic effects of prolonged exercise 74 and that there may be additive effects of co-ingesting HMB with creatine 75,76  Glutamine. Glutamine is the most plentiful non-essential amino acid in the body and plays a number of important physiological roles 36 . Glutamine has been reported to increase cell volume and stimulate protein [94][95][96] and glycogen synthesis 97 . Theoretically, glutamine supplementation prior to and/or following exercise (e.g., 6-10 g) may help to optimize cell hydration and protein synthesis during training leading to greater gains in muscle mass and strength 36,98 . In support of this hypothesis, a recent study by Colker and associates 99 found that subjects who supplemented their diet with glutamine (5 grams) and BCAA (3 grams) enriched whey protein during training promoted about a 2 pound greater gain in muscle mass and greater gains in strength than ingesting whey protein alone. Although more data is needed, there appears to be a strong scientific rationale and some preliminary evidence to indicate that glutamine may help build muscle. While future studies may find some ergogenic value of ecdysterones, it is our view that it is too early to tell whether phytoecdysteroids serve as a safe and effective nutritional supplement for athletes.

Growth Hormone Releasing Peptides (GHRP) and Secretogues.
Research has indicated that growth hormone releasing peptides (GHRP) and other non-peptide compounds (secretagogues) appear to help regulate growth hormone (GH) release 110,111 . These observations have served as the basis for development of nutritionally-based GH stimulators (e.g., amino acids, pituitary peptides, "pituitary substances", macuna pruriens, broad bean, alpha GPC, etc). Although there is clinical evidence that pharmaceutical grade GHRP's and some nonpeptide secretagogues can increase GH and IGF-1 levels at rest and in response to exercise, it is currently unknown whether any of these nutritional alternatives would increase GH and/or affect training adaptations.
Isoflavones. Isoflavones are naturally occurring non-steroidal phytoestrogens that have a similar chemical structure as the ipriflavone (a synthetic flavonoid drug used in the treatment of osteoporosis) [112][113][114] . For this reason, soy protein (which is an excellent source of isoflavones) and isoflavone extracts have been investigated in the possible treatment of osteoporosis. Results of these studies have shown promise in preventing declines in bone mass in post-menopausal women as well as reducing risks to side effects associated with estrogen replacement therapy. More recently, the isoflavone extracts 7-isopropoxyisoflavone (ipriflavone) and 5-methyl-7-methoxy-isoflavone (methoxyisoflavone) have been marketed as "powerful anabolic" substances. These claims have been based on research described in patents filed in Hungary in the early 1970s 115,116 . Although the data presented in the patents are interesting, there is currently no peerreviewed data indicating that isoflavone supplementation affects exercise, body composition, or training adaptations.

Ornithine-α-ketoglutarate (OKG).
OKG is another nutrient believed to possess anabolic/catabolic effect. Animal and clinical studies have suggested that patients administered OKG experienced improved protein balance 115,116 . Theoretically, OKG may provide some value for athletes engaged in intense training. A recent study by Chetlin and colleagues 117 reported that OKG supplementation (10 grams/day) during 6weeks of resistance training promoted greater gains in bench press. However, no significant differences were observed in squat strength, training volume, gains in muscle mass, or fasting insulin and growth hormone. Therefore, additional research is needed before conclusions can be drawn.

Sulfo-Polysaccharides (Myostatin Inhibitors).
Myostatin or growth differentiation factor 8 (GDF-8) is a transforming growth factor that has been shown to serve as a genetic determinant of the upper limit of muscle size and growth 118 . Recent research has indicated that eliminating and/or inhibiting myostatin gene expression in mice 119 and cattle 120-122 promotes marked increases in muscle mass during early growth and development. The result is that these animals experience what has been termed as a "double-muscle" phenomenon apparently by allowing muscle to grow beyond its normal genetic limit. In agriculture research, eliminating and/or inhibiting myostatin may serve as an effective way to optimize animal growth leading to larger, leaner, and a more profitable livestock yield. In humans, inhibiting myostatin gene expression has been theorized as a way to prevent or slow down muscle wasting in various diseases, speed up recovery of injured muscles, and/or promote increases in muscle mass and strength in athletes 123 . While these theoretical possibilities may have great promise, research on the role of myostatin inhibition on muscle growth and repair is in the very early stagesparticularly in humans. There is some evidence that myostatin levels are higher in the blood of HIV positive patients who have experience muscle wasting and that myostatin levels negatively correlate with muscle mass 118 . There is also evidence that myostatin gene expression may be fiber specific and that myostatin levels may be influenced by immobilization in animals 124 . Additionally, a recent study by Ivey and colleagues 123 reported that female athletes with a less common myostatin allele (a genetic subtype that may be more resistant to myostatin) experienced greater gains in muscle mass during training and less loss of muscle mass during detraining. No such pattern was observed in men with varying amounts of training histories and muscle mass. These early studies suggest that myostatin may play a role in regulating muscle growth to some degree. Recently, some nutrition supplement companies have marketed sulfo-polysaccharides (derived from a sea algae called Cytoseira canariensis) as a way to partially bind the myostatin protein in serum. Although this theory is interesting and studies examining this hypothesis are underway, there is currently no published data supporting the use of sulfo-polysaccharides as a muscle building supplement.

Smilax Officinalis (SO).
SO is a compound which contains plant sterols purported to enhance immunity as well as provide an androgenic effect on muscle growth 1 . Some data supports the potential immune enhancing effects of SO. However, we are not aware of any data that show that SO supplementation increases muscle mass during training.
Zinc/Magnesium Aspartate (ZMA). ZMA formulations have recently become a popular supplement purported to promote anabolism at night. The theory is based on studies suggesting that zinc and magnesium deficiency may reduce the production of testosterone and insulin like growth factor (IGF-1). ZMA supplementation has been theorized to increase testosterone and IGF-1 leading to greater recovery, anabolism, and strength during training. In support of this theory, Brilla and Conte 125 reported that a zinc-magnesium formulation increased testosterone and IGF-1 (two anabolic hormones) leading to greater gains in strength in football players participating in spring training. While these data are interesting, more research is needed to further evaluate the role of ZMA on body composition and strength during training before conclusions can be drawn.

Apparently Ineffective
Boron. Boron is a trace mineral proposed to increase testosterone levels and promote anabolism. Several studies have evaluated the effects of boron supplementation during training on strength and body composition alterations. These studies indicate that boron supplement (2.5 mg/d) appears to have no impact on muscle mass or strength 126,127 .

Chromium.
Chromium is a trace mineral that is involved in carbohydrate and fat metabolism. Clinical studies have suggested that chromium may enhance the effects of insulin particularly in diabetic populations.
Since insulin is an anti-catabolic hormone and has been reported to affect protein synthesis, chromium supplementation has been theorized to serve as an anabolic nutrient. Theoretically, this may increase anabolic responses to exercise. Although some initial studies reported that chromium supplementation increased gains in muscle mass and strength during training particularly in women [128][129][130] , most well-controlled that have been conducted since then have reported no benefit in healthy individuals taking chromium (200-800 mcg/d) for 4 to 16-weeks during training [131][132][133][134][135][136][137] . Consequently, it appears that although chromium supplementation may have some therapeutic benefits for diabetics, chromium does not appear to be a muscle-building nutrient for athletes.

Conjugated Linoleic Acids (CLA).
Animal studies indicate that adding CLA to dietary feed decreases body fat, increases muscle and bone mass, has anti-cancer properties, enhances immunity, and inhibits progression of heart disease [138][139][140] . Consequently, CLA supplementation in humans has been suggested to help manage body composition, delay loss of bone, and provide health benefit. Although animal studies are impressive [141][142][143] and a some studies suggests benefit at some but not all dosages 144,145 , most studies conducted on humans show little to no effect on body composition or muscle growth. 146,147 Gamma Oryzanol (Ferulic Acid). Gamma oryzanol is a plant sterol theorized to increase anabolic hormonal responses during training 148 . Although data are limited, one study reported no effect of 0.5 g/d of gamma oryzanol supplementation on strength, muscle mass, or anabolic hormonal profiles during 9weeks of training 149 .

Anabolic Steroids & Prohormones.
Testosterone and growth hormone are two primary hormones in the body that serve to promote gains in muscle mass (i.e., anabolism) and strength while decreasing muscle breakdown (catabolism) and fat mass [150][151][152][153][154] . Testosterone also promotes male sex characteristics (e.g., hair, deep voice, etc) 154 . Low level anabolic steroids are often prescribed by physicians to prevent loss of muscle mass for people with various diseases and illnesses [155][156][157][158][159][160][161][162][163][164][165][166] . It is well known that athletes have experimented with large doses of anabolic steroids in an attempt to enhance training adaptations, increase muscle mass, and/or promote recovery during intense training [150][151][152][153][154] . Research has generally shown that use of anabolic steroids and growth hormone during training can promote gains in strength and muscle mass 150 189,190 .

Weight Loss Supplements
Although exercise and proper diet remain the best way to promote weight loss and/or manage body composition, a number of nutritional approaches have been investigated as possible weight loss methods (with or without exercise). The following overviews the major types of weight loss products available and discusses whether any available research supports their use. See Table 3 for a summary.

Low Calorie Diet Foods & Supplements.
Most of the products in this category represent low fat/carbohydrate, high protein food alternatives 191 . They typically consist of pre-packaged food, bars, MRP, or RTD supplements. They are designed to provide convenient foods/snacks to help people follow a particular low calorie diet plan. In the scientific literature, diets that provide less than 1000 calories per day are known as very low calorie diets (VLCD's). Pre-packaged food, MRP's, and/or RTD's are often provided in VLCD plans to help people cut calories. In most cases, VLCD plans recommend behavioral modification and that people start a general exercise program.
Research on the safety and efficacy of people maintaining VLCD's generally indicate that they can promote weight loss. For example, Hoie et al 192 reported that maintaining a VLCD for 8-weeks promoted a 27 lbs (12.6%) loss in total body mass, a 21 lbs loss in body fat (23.8%), and a 7 lbs (5.2%) loss in lean body mass in 127 overweight volunteers. Bryner and colleagues 193 reported that addition of a resistance training program while maintaining a VLCD (800 kcal/d for 12-weeks) resulted in a better preservation of lean body mass and resting metabolic rate compared to subjects maintaining a VLCD while engaged in an endurance training program. Kern and coworkers 194 reported that a medically supervised weight loss program involving behavioral modification and VLCD promoted a 51 lbs weight loss and that 61% of subjects maintained at least 50% of the weight loss at 12 and 18 months follow-up. Recent studies indicate that high protein/low fat VLCD's may be better than high carbohydrate/low fat diets in promoting weight loss 32,[195][196][197][198] . The reason for this is that typically when people lose weight about 40-50% of the weight loss is muscle which decreases resting energy expenditure.
Increasing protein intake during weight loss helps preserve muscle mass and resting energy expenditure to a better degree than high carbohydrate diets 199 . These findings and others indicate that VLCD's (typically using MRP's and/or RTD's as a means to control caloric intake) can be effective particularly as part of an exercise and behavioral modification program. Most people appear to maintain at least half of the initial weight lost for 1-2 years but tend to regain most of the weight back within 2-5 years. Therefore, although these diets may help people lose weight on the short-term, it is essential people who use them follow good diet and exercise practices in order to maintain the weight loss.

Ephedra, Caffeine, and Silicin.
Thermogenics are supplements designed to stimulate metabolism thereby increasing energy expenditure and promote weight loss. Despite these findings, the Food and Drug Administration (FDA) has recently banned the sale of ephedra containing supplements. The rationale has been based on reports to adverse event monitoring systems and in the media suggesting a link between intake of ephedra and a number of severe medical complications (e.g., high blood pressure, elevated heart rate, arrhythmias, sudden death, heat stroke, etc) 210,211 . Although results of available clinical studies do not show these types of adverse events and the ban is in the process of being contested legally, ephedra is no longer available as an ingredient in dietary supplements. Consequently, thermogenic supplements now contain other nutrients believed to increase energy expenditure (e.g., synephrine, green tea, etc). Anyone contemplating taking thermogenic supplements should carefully consider the potential side effects, discuss possible use with a knowledgeable physician, and be careful not exceed recommended dosages.

Possibly Effective
High Fiber Diets. One oldest and most common methods of suppressing the appetite is to eat a high fiber diet. Ingesting high fiber foods (fruits, vegetables) or fiber supplements increase the feeling of fullness (satiety). They typically allow you to feel full while ingesting fewer calories. Theoretically, maintaining a high fiber diet may serve to help decrease the amount of food you eat. In addition, high fiber diets/supplements have also been purported to help lower cholesterol and blood pressure as well as help diabetics manage glucose and insulin levels. Some of the research conducted on high fiber diets indicates that they provide some benefit, particularly in diabetic populations. For example, Raben et al 212 reported that subjects maintaining a low fat/high fiber diet for 11 weeks lost about 3 lbs of weight and 3.5 lbs of fat. Other studies report either no significant effects or modest amounts of fat loss. High fiber/low fat diets have also been found to help reduce cholesterol. Consequently, although maintaining a low fat / high fiber diet may have some health benefits, they do not appear to promote a significant amount of weight or fat loss.

Calcium.
Research has indicated that calcium modulates 1,25-diydroxyvitamin D which serves to regulate intracellular calcium levels in fat cells [213][214][215] . Increasing dietary availability of calcium reduces 1,25diydroxyvitamin D and promotes reductions in fat mass in animals [213][214][215] . Dietary calcium has been shown to suppress fat metabolism and weight gain during periods of high caloric intake 213,216 . Further, increasing calcium intake has been shown to increase fat metabolism and preserve thermogenesis during caloric restriction 213,216,217 . In support of this theory, Davies  Phosphates. The role of sodium and calcium phosphate on energy metabolism and exercise performance has been studied for decades 36 .
These studies have revealed that sodium phosphate supplementation appears to possess ergogenic properties particularly in endurance exercise events 219,220 . More recently, phosphate supplementation has also been suggested to affect energy expenditure. For example, Kaciuba-Uscilko and colleagues 221 reported that phosphate supplementation during a 4-week weight loss program increased resting metabolic rate (RMR) and respiratory exchange ratio (suggesting greater carbohydrate utilization and caloric expenditure) during submaximal cycling exercise. In addition, Nazar and coworkers 222 reported that phosphate supplementation during an 8-week weight loss program increased RMR by 12-19% and prevented a normal decline in thyroid hormones. Although the rate of weight loss was similar in this trial, results suggest that phosphate supplementation may influence metabolic rate possibly by affecting thyroid hormones. Consequently, it is possible that phosphate could serve as a potential thermogenic nutrient in non-ephedrine based supplements. Additional research is necessary to test this hypothesis.

Green Tea Extract.
Green tea is one of the more interesting herbal supplements that has recently been suggested to affect weight loss. Green tea contains high amounts of caffeine and catechin polyphenols. Research suggests that catechin polyphenols possess antioxidant properties 223 . In addition, green tea has also been theorized to increase energy expenditure by stimulating brown adipose tissue thermogenesis. In support of this theory, Dulloo et al 224,225 reported that green tea supplementation in combination with caffeine (e.g., 50 mg caffeine and 90 mg epigallocatechin gallate taken 3-times per day) significantly increased 24-hour energy expenditure and fat utilization in humans. The thermogenic effects of green tea supplementation were much greater than when an equivalent amount of caffeine was evaluated suggesting a synergistic effect. Theoretically, increases in energy expenditure may help individuals lose weight and/or manage body composition.
Calcium Pyruvate. Calcium Pyruvate is supplement that hit the scene about five or six years ago with great promise. The theoretical rationale was based on studies from the early 1990s that reported that calcium pyruvate supplementation (16 -25 g/d with or without dihydroxyacetone phosphate [DHAP]) promoted fat loss in overweight/obese patients following a medially supervised weight loss program [226][227][228] . Although the mechanism for these findings was unclear, the researchers speculated that it might be related to appetite suppression and/or altered carbohydrate and fat metabolism. Since calcium pyruvate is very expensive, several studies have attempted to determine whether ingesting smaller amounts of calcium pyruvate (6-10 g/d) affect body composition in untrained and trained populations. Results of these studies are mixed. Kalman and colleagues 229 reported that calcium pyruvate supplementation (6 g/d for 6-weeks) significantly decreased body weight (-1.2 kg), body fat (-2.5 kg), and percent body fat (-2.7%). However, Stone and colleagues 230 reported that pyruvate supplementation did not affect hydrostatically determined body composition during 5-weeks of in-season college football training. These findings indicate that although there is some supportive data indicating that calcium pyruvate supplementation may enhance fat loss when taken at high doses (6-16 g/d), there is no evidence that ingesting the doses typically found in pyruvate supplements (0.5 -2 g/d) has any affect on body composition.

Too Early to Tell
Gymnema Sylvestre. Gymnema Sylvestre is a relatively new supplement. It is purported to affect glucose and fat metabolism as well as inhibit sweet cravings. In support of these contentions, some recent data have been published by Shigematsu and colleagues 231,232 indicating that short and long-term oral supplementation of gymnema sylvestre in rats fed normal and high-fat diets may have some positive effects on fat metabolism, blood lipid levels, and/or weight gain/fat deposition. Although these findings are interesting, we are aware of no published studies that have evaluated the effects of gymnema sylvestre supplementation on lipid metabolism or body composition in humans. Consequently, more research is needed before conclusions can be drawn.
Chitosan. Chitosan has been marketed as a weight loss supplement for several years. It is purported to inhibit fat absorption and lower cholesterol. Several animal studies report decreased fat absorption, increased fecal fat content, and/or lower cholesterol following chitosan feedings [233][234][235][236] . However, the effects in humans appear to be less impressive. For example, although there is some data suggesting that chitosan supplementation may lower blood lipids in humans, 237 other studies report no effects on fecal fat content 238 or body composition alterations 239, 240 when administered to people following their normal diet. It seems that people may be prone to eat more when they know they are taking a fat blocking supplement in a similar way people tend to eat more when the consume low-fat foods. Whether chitosan may promote greater amounts of fat loss when people are put on a controlled diet is unclear.

Non-Ephedra Containing Thermogenics.
Since the safety of ephedra supplements has come into question, a number of supplement companies have been looking for alternatives to ephedra such as Citrus Aurantum or Bitter Orange (synephrine), thyroid stimulators, and various herbs and peppers (cayenne, black pepper, ginger root, etc) 191 . Of these, Citrus Aurantum (synephrine) appears to have the most promise 241,242 . Some studies suggest that synephrine may increase metabolism without significantly affecting heart rate and blood pressure. However, it is unclear whether dietary supplementation of Citrus Aurantum may enhance weight loss. A number of thyroid stimulating supplements have also been marketed. Most contain nutrients (e.g., guggulsterones, 3, 5-Diiodo-L-Thyronine, etc.) believed to enhance the conversion of triidiothyronine (T3) to thyroxin (T4) or increase availability of T2 (diidiothyronine) or T3 which would theoretically increase basal metabolic rate (resting caloric expenditure) and promote weight loss 243,244 . However, while thyroid medications can effectively increase metabolic rate 245 , it is unclear whether these supplements can promote weight loss. Additionally, several of these types of supplements have been recently pulled by the FDA due to adverse health outcomes reported among people using these types of supplements particularly if they also contain usnic acid.

Phosphatidyl Choline (Lecithin).
Choline is considered an essential nutrient that is needed for cell membrane integrity and to facilitate the movement of fats in and out of cells. It is also a component of the neurotransmitter acetylcholine and is needed for normal brain functioning, particularly in infants. For this reason, phosphatidyl choline (PC) has been purported as a potentially effective supplement to promote fat loss as well as improve neuromuscular function. There is some data from animal studies that supports the potential value of PC as a weight loss supplement 246 . There has also been some interest in determining the potential ergogenic value of choline supplementation during endurance exercise 247,248 . However, it is currently unclear whether PC supplementation affects body composition in humans.

Betaine.
Betaine is a compound that is involved in the metabolism of choline and homocysteine. A number of studies have evaluated the effects of betaine feedings on liver metabolism, fat metabolism, and fat deposition in animals 249,250 . There has also been interest in determining whether betaine supplementation may help lower homocysteine levels which has recently been identified as a marker of risk to heart disease 251 . For this reason, betaine supplements have been marketed as a supplement designed to promote heart health as well as a weight loss. Although the potential theoretical rationale of betaine supplementation is interesting, it is currently unclear whether betaine supplementation may serve as an effective weight loss supplement in humans.

Coleus Forskohlii (Forskolin).
Forskolin is another relatively new weight loss supplement. Forskolin is a plant native to India that has been used for centuries in traditional Ayurvedic medicine primarily to treat skin disorders and respiratory problems 252,253 . A considerable amount of research has evaluated the physiological and potential medical applications of forskolin over the last 25 years. Forskolin has been reported to reduce blood pressure, increase the hearts ability to contract, help inhibit platelet aggregation, improve lung function, and aid in the treatment of glaucoma [252][253][254] . With regard to weight loss, forskolin has been reported to increase cyclic AMP and thereby stimulate fat metabolism [255][256][257] . Theoretically, forskolin may therefore serve as an effective weight loss supplement. In support of this theory, Sabinsa Corporation (the principle source for Forskolin in the U.S.) reported that forskolin supplementation (250 mg of a 10% forskolin extract taken twice daily for 8-weeks) administered in an open label manner to six overweight females promoted a 7.25 lbs loss in body weight and a 7.7% decrease bioelectrical impedance (BIA) determined body fat 258 . Although this was not a placebo controlled double blind study and BIA is not the most accurate method of assessing body composition, these preliminary findings provide some support to contentions that forskolin supplementation may promote fat loss. Another recent study suggested that supplementing the diet with coleus forskohlii in overweight women helped maintain weight and was not associated with any clinically significant adverse events 259 . Additional research is needed before conclusions can be drawn.

Dehydroepiandrosterone (DHEA) and 7-
Keto DHEA. Dehydroepiandrosterone (DHEA) and its sulfated conjugate DHEAS represent the most abundant adrenal steroids in circulation 260 . Although, DHEA is considered a weak androgen, it can be converted to the more potent androgens testosterone and dihydrotestosterone in tissues. In addition, DHEAS can be converted into androstenedione and testosterone. DHEA levels have been reported to decline with age in humans 261 .
The decline in DHEA levels with aging has been associated with increased fat accumulation and risk to heart disease 262 .
Since DHEA is a naturally occurring compound, it has been suggested that dietary supplementation of DHEA may help maintain DHEA availability, maintain and/or increase testosterone levels, reduce body fat accumulation, and/or reduce risk to heart disease as one ages 260,262 . Although animal studies have generally supported this theory, the effects of DHEA supplementation on body composition in human trials have been mixed. For example, Nestler and coworkers 263 reported that DHEA supplementation (1,600 mg/d for 28-d) in untrained healthy males promoted a 31% reduction in percentage of body fat. However, Vogiatzi and associates 264 reported that DHEA supplementation (40 mg/d for 8 wks) had no effect on body weight, percent body fat, or serum lipid levels in obese adolescents. More recently, 7-keto DHEA has been marketed as a potentially more effective form of DHEA. 7-keto DHEA is a precursor to DHEA that is believed to possess lypolytic properties. Although data are limited, Kalman and colleagues and coworkers 265 reported that 7keto DHEA supplementation (200 mg/d) during 8-weeks of training promoted a greater loss in body mass and fat mass while increasing T3. No significant effects were observed on thyroid stimulating hormone (TSH), T4, or other hormones. Although more research is needed, these findings provide some support to contentions that 7keto DHEA may serve as an effective weight loss supplement. However, additional research is needed before definitive conclusions can be made.
Psychotropic Nutrients/Herbs. This is a relatively new type of weight loss supplement category. Psychotropic nutrients/herbs often contain things like St. John's Wart, Kava, Ginkgo Biloba, Ginseng, and L-Tyrosine.
They are believed to serve as naturally occurring antidepressants, relaxants, and mental stimulants. The theoretical rationale regarding weight loss is that they may help people fight depression or maintain mental alertness while dieting. Although a number of studies support potential role as naturally occurring psychotropics or stimulants, the potential value in promoting weight loss is unclear.

Apparently Ineffective
Chromium. Interest in chromium as a potential body composition modifier emanated from studies suggesting that chromium may enhance insulin sensitivity/glucose disposal in diabetics. Initial studies reported that chromium supplementation during resistance training improved fat loss and gains in lean body mass [128][129][130] . However, recent studies using more accurate methods of assessing body composition have mostly reported no effects on body composition in healthy non-diabetic individuals [131][132][133][134][135][136][137] . For example, Walker and colleagues 132 reported that chromium supplementation (200 µg/d for 14-weeks) did not affect body composition alterations during training in healthy wrestlers. Likewise, Lukaski et al 136 reported that 8-weeks of chromium supplementation during resistance training did not affect strength or DEXA determined body composition changes. Therefore, chromium supplementation does not appear to promote fat loss.

Conjugated Linoleic Acids (CLA).
CLA is a term used to describe a group of positional and geometric isomers of linoleic acid that contain conjugated double bonds. Adding CLA to the diet has been reported to possess significant health benefits in animals 138,266 .
In terms of weight loss, CLA feedings to animals have been reported to markedly decrease body fat accumulation 138,139,143 .
Consequently, CLA has been marketed as a health and weight loss supplement since the mid 1990s. Although basic research in animals is very promising, the effect of CLA supplementation in humans is less clear.
There are some data suggesting that CLA supplementation may modestly promote fat loss and/or increases in lean mass 144,[267][268][269][270][271] . However, other studies indicate that CLA supplementation (1.7 to 12 g/d for 4-weeks to 6-months) has limited to no effects on body composition alterations in untrained or trained populations 144,146,147,267,[272][273][274] . The reason for the discrepancy in research findings has been suggested to be due to differences in purity and the specific isomer studied. For instance, early studies in humans showing no effect used CLA that contained all 24 isomers. Today, most labs studying CLA use 50-50 mixtures containing the trans-10,cis-12 and cis-9,trans-11 isomers, the former of which being recently implicated in positively altering body composition. In our view, although CLA supplementation may have promise to promote general health, additional research is needed to determine if specific isomers of CLA may affects body composition in humans before conclusions can be made.

Garcinia Cambogia (HCA).
HCA is a nutrient that has been hypothesized to increase fat oxidation by inhibiting citrate lyase and lipogenesis 275 284,285 indicated that although herbal diuretics promoted a small amount of dehydration (about 0.3% in one day), they were not nearly as effective as a common diuretic drug (about 3.1% dehydration in one day). Consequently, although more research is needed, the potential value of herbal diuretics as a weight loss supplement appears limited.

Performance Enhancement Supplements
A number of nutritional supplements have been proposed to enhance exercise performance. Some of these nutrients have been described above. Table 3 categorizes the proposed ergogenic nutrients into apparently safe and effective, possibly effective, too early to tell, and apparently ineffective. Weight gain supplements purported to increase muscle mass may also have ergogenic properties if they also promote increases in strength. Similarly, some sports may benefit from reductions in fat mass. Therefore, weight loss supplements that help athletes manage body weight and/or fat mass may also posses some ergogenic benefit. The following describes which supplements may or may not affect performance that were not previously described. Based on this analysis, Table 4 summarizes the general nutritional recommendations for athletes and which dietary supplements may help power and endurance athletes.

Apparently Effective
Water and Sports Drinks. Preventing dehydration during exercise is one of the keys of maintaining exercise performance (particularly in hot/humid environments). People engaged in intense exercise or work in the heat need to frequently ingest water or sports drinks (e.g., 1-2 cups every 10 -15 minutes). The goal should be not to lose Creatine. Earlier we indicated that creatine supplementation is one of the best supplements available to increase muscle mass and strength during training. However, creatine has also been reported to improve exercise capacity in a variety of events 54 . This is particularly true when performing high intensity, intermittent exercise such as multiple sets of weight lifting, repeated sprints, and/or exercise involving sprinting and jogging (e.g., soccer) 54 . Although studies evaluating the ergogenic value of creatine on endurance exercise performance are mixed, endurance athletes may also theoretically benefit in several ways. For example, increasing creatine stores prior to carbohydrate loading (i.e., increasing dietary carbohydrate intake before competition in an attempt to maximize carbohydrate stores) has been shown to improve the ability to store carbohydrate [286][287][288] . Further, coingesting creatine with carbohydrate has been shown to optimize creatine and carbohydrate loading 289 . Most endurance athletes also perform interval training (sprint or speed work) in an attempt to improve anaerobic threshold. Since creatine has been reported to enhance interval sprint performance, creatine supplementation during training may improve training adaptations in endurance athletes 290,291 . Finally, many endurance athletes lose weight during their competitive season. Creatine supplementation during training may help people maintain weight.
Sodium Phosphate. We previously mentioned that sodium phosphate supplementation may increase resting energy expenditure and therefore could serve as a potential weight loss nutrient. However, most research on sodium phosphate has actually evaluated the potential ergogenic value. A number of studies indicated that sodium phosphate supplementation (e.g., 1 gram taken 4 times daily for 3-6 days) can increase maximal oxygen uptake (i.e., maximal aerobic capacity) and anaerobic threshold by 5-10% 219,220,292,293 . These finding suggest that sodium phosphate may be highly effective in improving endurance exercise capacity. Other forms of phosphate (i.e., calcium phosphate, potassium phosphate) do not appear to possess ergogenic value.

Sodium Bicarbonate (Baking Soda).
During high intensity exercise, acid (H+) and carbon dioxide (CO 2 ) accumulate in the muscle and blood. One of the ways you get rid of the acidity and CO 2 is to buffer the acid and CO 2 with bicarbonate ions. The acid and CO 2 are then removed in the lungs. Bicarbonate loading (e.g., 0.3 grams per kg taken 60-90 minutes prior to exercise or 5 grams taken 2 times per day for 5-days) has been shown to be an effective way to buffer acidity during high intensity exercise lasting 1-3 minutes in duration [294][295][296][297] . This can improve exercise capacity in events like the 400 -800 m run or 100 -200 m swim 298 . Although bicarbonate loading can improve exercise, some people have difficulty with their stomach tolerating bicarbonate as it may cause gastrointestinal distress.
Caffeine. Caffeine is a naturally derived stimulant found in many nutritional supplements typically as Gaurana, Bissey Nut, or Kola. Caffeine can also be found in coffee, tea, soft drinks, energy drinks, and chocolate. Studies indicate that ingestion of caffeine (e.g., 3-9 mg/kg taken 30 -90 minutes before exercise) can spare carbohydrate use during exercise and thereby improve endurance exercise capacity 295,299 .
People who drink caffeinated drinks regularly, however, appear to experience less ergogenic benefits from caffeine 300 . Additionally, some concern has been expressed that ingestion of caffeine prior to exercise may contribute to dehydration although recent studies have not supported this concern 301-303 . Caffeine doses above 9 mg/kg can result in urinary caffeine levels that surpass the doping threshold for many sport organizations. Suggestions that there is no ergogenic value to caffeine supplementation is not supported by the preponderance of available scientific studies.

Possibly Effective
Post-Exercise Carbohydrate and Protein. Ingesting carbohydrate and protein following exercise enhances carbohydrate storage and protein synthesis. Theoretically, ingesting carbohydrate and protein following exercise may lead to greater training adaptations. In support of this theory, Esmarck and coworkers 93 found that ingesting carbohydrate and protein immediately following exercise doubled training adaptations in comparison to waiting until 2hours to ingest carbohydrate and protein.
Additionally, Tarnopolsky and associates 304 reported that post-exercise ingestion of carbohydrate with protein promoted as much strength gains as ingesting creatine with carbohydrate during training. These findings underscore the importance of post-exercise carbohydrate and protein ingestion.
Glutamine. As described above, glutamine has been shown to influence protein synthesis and help maintain the immune system. Theoretically, glutamine supplementation during training should enhance gains in strength and muscle mass as well as help athletes tolerate training to a better degree.
Although there is some evidence that glutamine supplementation with protein can improve training adaptations, more research is needed to determine the ergogenic value in athletes.

Essential Amino Acids (EAA).
Ingestion of 3-6 grams of EAA following resistance exercise has been shown to increase protein synthesis [84][85][86][87][88][89][90][91][92] . Theoretically, ingestion of EAA after exercise should enhance gains in strength and muscle mass during training. While there is sound theoretical rationale, it is currently unclear whether following this strategy would lead to greater training adaptations and/or whether EAA supplementation would be better than simply ingesting carbohydrate and a quality protein following exercise.

Branched Chain Amino Acids (BCAA).
Ingestion of BCAA (e.g., 6-10 grams per hour) with sports drinks during prolonged exercise would theoretically improve psychological perception of fatigue (i.e., central fatigue). Although there is strong rationale, the effects of BCAA supplementation on exercise performance is mixed with some studies suggesting an improvement and others showing no effect 36 [312][313][314][315][316] . However, it is unclear whether dietary supplements containing botanical ephedrine (i.e., ephedra) and caffeine (e.g., kola nut) have similar effects on performance. Further, since most sport organizations ban use of ephedrine the potential use in athletes appears limited.

Too Early to Tell
A number of supplements purported to enhance performance and/or training adaptation fall under this category. This includes the weight gain and weight loss supplements listed in Table 3 as well as the following supplements not previously described in this category.

Medium Chain Triglycerides (MCT).
MCT's are shorter chain fatty acids that can easily enter the mitochondria of the cell and be converted to energy through fat metabolism 317 . Studies are mixed as to whether MCT's can serve as an effective source of fat during exercise metabolism and/or improve exercise performance [318][319][320][321][322] .
Ribose. Ribose is a 3-carbon carbohydrate that is involved in the synthesis of adenosine triphosphate (ATP) in the muscle (the useable form of energy). Clinical studies have shown that ribose supplementation can increase exercise capacity in heart patients [323][324][325][326][327] . For this reason, ribose has been suggested to be an ergogenic aid for athletes. Although more research is needed, most studies show no ergogenic value of ribose supplementation on exercise capacity in health untrained or trained populations [328][329][330] .

Apparently Ineffective
Inosine. Inosine is a building block for DNA and RNA that is found in muscle. Inosine has a number of potentially important roles that may enhance training and/or exercise performance 331 . Although there is some theoretical rationale, available studies indicate that inosine supplementation has no apparent affect on exercise performance capacity [332][333][334] .

Supplements to Promote General Health
In addition to the supplements previously described, several nutrients have been suggested to help athletes stay healthy during intense training. For example, the American Medical Association recently recommended that all Americans ingest a daily low-dose multivitamin in order to ensure that people get a sufficient amount of vitamins and minerals in their diet. Although one-a-day vitamin supplementation has not been found to improve exercise capacity in athletes, it may make sense to take a daily vitamin supplement for health reasons. Glucosomine and chondroitin have been reported to slow cartilage degeneration and reduce the degree of joint pain in active individuals which may help athletes postpone and/or prevent joint problems 335,336 . Vitamin C, glutamine, Echinacea, and zinc have been reported to enhance immune function 42,[337][338][339] . Consequently, some sport nutritionists recommend that athletes who feel a cold coming on take these nutrients in order to enhance immune function 42,[337][338][339] .
Similarly, nutrients such as vitamins E and C may help restore overwhelmed anti-oxidant defenses exhibited by athletes and reduce the risk of numerous chronic diseases 340 . Creatine, calcium ß-HMB, BCAA, and Lcarnitine have been shown to help athletes tolerate heavy training periods 36,74,80,81,83,[341][342][343][344] . Finally, omega-3 fatty acids, in supplemental form, are now endorsed by the American Heart Association for heart health in certain individuals 345 . This supportive supplement position stems from: 1.) an inability to consume cardio-protective amounts by diet alone; and, 2.) the mercury contamination sometimes present in wholefood sources of DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid) found in fatty fish. Consequently, prudent use of these types of nutrients at various times during training may help athletes stay healthy and/or tolerate training to a greater degree 37 .

SUMMARY
Numerous nutritional and herbal products are marketed to promote weight gain, weight loss, and/or improve performance. Most have a theoretical basis for use but little data supporting safety and efficacy in athletes. A number are heavily marketed despite data indicating that they do not affect body composition, performance, and/or training adaptations at the dosages recommended. It is in these particular situations that unsupported claims explicitly or implicitly endorsed by sport nutrition specialists constitute fraud and/ or "quackery". Prudent training, maintaining an energy balance and nutrient dense diet, proper timing of nutrient intake, and obtaining adequate rest are the cornerstones to enhancing performance and/or training adaptations. Use of a limited number of nutritional supplements that research has supported can help improve energy availability (e.g., sports drinks, carbohydrate, creatine, caffeine, etc) and/or promote recovery (carbohydrate, protein, essential amino acids, etc) can provide additional benefit in certain instances. The sport nutrition specialist should stay up to date regarding the role of nutrition on exercise so they can provide honest and accurate information to their students, clients, and/or athletes about the role of nutrition and dietary supplements on performance and training. Furthermore, the sport nutrition specialist should actively participate in exercise nutrition research; write unbiased scholarly reviews for journals and lay publications; help disseminate the latest research findings to the public so they can make informed decisions about appropriate methods of exercise, dieting, and/or whether various nutritional supplements can affect health, performance, and/or training; and, disclose any commercial or financial conflicts of interest during such promulgations to the public. Finally, sport nutrition specialists can challenge companies who sell exercise equipment and/or nutritional supplements to develop scientifically based products, conduct research on their products, and honestly market the results of studies so consumers can make informed decisions. Has been marketed as a supplement that will improve muscle mass, strength, and aerobic power in the lactic acid and oxygen systems. It also may have a calming effect that has been linked to an improved mental strength.
In well-nourished athletes, pyridoxine failed to improve aerobic capacity, or lactic acid accumulation 353 . However, when combined with vitamins B 1 and B 12, it may increase serotonin levels and improve fine motor skills that may be necessary in sports like pistol shooting and archery 357

mcg/d
A coenzyme involved in the production of DNA and serotonin. DNA is important in protein and red blood cell synthesis. Theoretically, it would increase muscle mass, the oxygencarrying capacity of blood, and decrease anxiety.
In well-nourished athletes, no ergogenic effect has been reported. However, when combined with vitamins B 1 and B 6 , cyanocobalamin has been shown to improve performance in pistol shooting 358 . This may be due to increased levels of serotonin, a neurotransmitter in the brain, which may reduce anxiety. Folic acid (folate) 400 mcg/d Functions as a coenzyme in the formation of DNA and red blood cells. An increase in red blood cells could improve oxygen delivery to the muscles during exercise. Believed to be important to help prevent birth defects and may help decrease homocysteine levels.
Studies suggest that increasing dietary availability of folic acid during pregnancy can lower the incidence of birth defects 359 . Additionally, it may decrease homocysteine levels (a risk factor for heart disease) 360 . In well-nourished and folate deficient-athletes, folic acid did not improve exercise performance 361 . Pantothenic acid 5 mg/d Acts as a coenzyme for acetyl coenzyme A (acetyl CoA). This may benefit aerobic or oxygen energy systems.
Research has reported no improvements in aerobic performance with acetyl CoA supplementation. However, one study reported a decrease in lactic acid accumulation, without an improvement in performance 362 . Beta carotene None Serves as an antioxidant. Theorized to help minimize exerciseinduced lipid peroxidation and muscle damage.
Research indicates that beta carotene supplementation with or without other antioxidants can help decrease exercise-induced peroxidation. Over time, this may help athletes tolerate training. However, it is unclear whether antioxidant supplementation affects exercise performance 349 . Vitamin C Males 90 mg/d Females 75 mg/d Used in a number of different metabolic processes in the body. It is involved in the synthesis of epinephrine, iron absorption, and is an antioxidant. Theoretically, it could benefit exercise performance by improving metabolism during exercise. There is also evidence that vitamin C may enhance immunity.
In well-nourished athletes, vitamin C supplementation does not appear to improve physical performance 363,364 . However, there is some evidence that vitamin C supplementation (e.g., 500 mg/d) following intense exercise may decrease the incidence of upper respiratory tract infections 337  Boron has been marketed to athletes as a dietary supplement that may promote muscle growth during resistance training.
The rationale was primarily based on an initial report that boron supplementation (3 mg/d) significantly increased β-estradiol and testosterone levels in postmenopausal women consuming a diet low in boron.
Studies which have investigated the effects of 7 wk of boron supplementation (2.5 mg/d) during resistance training on testosterone levels, body composition, and strength have reported no ergogenic value 126,127 . There is no evidence at this time that boron supplementation during resistance-training promotes muscle growth.
Calcium 1000 mg/d (ages  Involved in bone and tooth formation, blood clotting, and nerve transmission. Stimulates fat metabolism. Diet should contain sufficient amounts, especially in growing children/adole 129 scents, female athletes, and postmenopausal women. Vitamin D needed to assist absorption.
Calcium supplementation may be beneficial in populations susceptible to osteoporosis 367 . Additionally, calcium supplementation has been shown to promote fat metabolism and help manage body composition 214,215 . Calcium supplementation provides no ergogenic effect on exercise performance. Chromium Males 35 mcg/d Females 25 mcg/d (ages  Chromium, commonly sold as chromium picolinate, has been marketed with claims that the supplement will increase lean body mass and decrease body fat levels.
Animal research indicates that chromium supplementation increases lean body mass and reduces body fat. Early research on humans reported similar results 129 , however, more recent well-controlled studies reported that chromium supplementation (200 to 800 mcg/d) does not improve lean body mass or reduce body fat 134,368 . Iron Males 8 mg/d Females 18 mg/d (age  Iron supplements are used to increase aerobic performance in sports that use the oxygen system. Iron is a component of hemoglobin in the red blood cell, which is a carrier of oxygen.
Most research shows that iron supplements do not appear to improve aerobic performance unless the athlete is iron-depleted and/or has anemia 369 .

Magnesium
Males 420 Females 320 Activates enzymes involved in protein synthesis. Involved in ATP reactions. Serum levels decrease with exercise. Some suggest that magnesium supplementation may improve energy metabolism/ATP availability.
Most well-controlled research indicates that magnesium supplementation (500 mg/d) does not affect exercise performance in athletes unless there is a deficiency 370,371 .
Phosphorus (phosphate salts) 700 mg/d Phosphate has been studied for its ability to improve all three energy systems, primarily the oxygen system or aerobic capacity.
Recent well-controlled research studies reported that sodium phosphate supplementation (4 g/d for 3 d) improved the oxygen energy system in endurance tasks 219,220,292 . There appears to be little ergogenic value of other forms of phosphate (i.e., calcium phosphate, potassium phosphate). More research is needed to determine the mechanism for improvement. Potassium 2000 mg/d* An electrolyte that helps regulate fluid balance, nerve transmission, and acid-base balance. Some suggest excessive increases or decreases in potassium may predispose athletes to cramping.
Although potassium loss during intense exercise in the heat has been anecdotally associated with muscle cramping, the etiology of cramping is unknown 372,373 . It is unclear whether potassium supplementation in athletes decreases the incidence of muscle cramping 374  Marketed as a supplement to increase aerobic exercise performance. Working closely with vitamin E and glutathione peroxidase (an antioxidant), selenium may destroy destructive free radical production of lipids during aerobic exercise.
Although selenium may reduce lipid peroxidation during aerobic exercise, improvements in aerobic capacity have not been demonstrated 375,376 .
Sodium 500 mg/d* During the first several days of intense training in the heat, a greater amount of sodium is lost in sweat. Additionally, prolonged ultraendurance exercise may decrease sodium levels leading to hyponatremia. Increasing salt availability during heavy training in the heat has been shown to help maintain fluid balance and prevent hyponatremia 374,377 . Vanadyl sulfate (vanadium)

None
Vanadium may be involved in reactions in the body that produce insulin-like effects on protein and glucose metabolism. Due to the anabolic nature of insulin, this has brought attention to vanadium as a supplement to increase muscle mass, enhance strength and power.
Limited research has shown that type 2 diabetics may improve their glucose control; however, there is no proof that vanadyl sulfate has any effect on muscle mass, strength, or power 189,190 .