Morrison et al.  compared supplement use by age group and found that young people consumed protein shakes/bars and creatine more than older people in the US. Other studies confirmed that the type of supplements used is age-related besides the type of exercise training [27–30]. Moreover, in Brazil, Goston and Correia  found that use of supplements was associated with the people who needed them less, since their diet appeared concurrently to be good or excellent. A similar observation has been described by Conner et al.  and Millen et al. . Many authors suggest that athletes need extra protein in their diet as food or as supplements [33–37], however regular gym attendees do not need these extra supplements [30, 34, 37]. When comparing protein supplements by age and strength exercise training groups between our data and others from different studies, it appears that US has the highest prevalence of users with 59.8% among 85 subjects  followed by Brazil with 40.1% of users among 231 subjects . Our survey showed 30.1% of supplement users amongst 207 subjects [Table 2]. According to other investigations, our study shows supplement consumption is more prevalent amongst men attending gyms [7, 20, 30]. Moreover, after stratifying protein supplements in whey protein shakes, egg protein shakes, protein bars, protein gel and protein shake blends, it appears that a majority of the users were taking whey protein shakes (50.0%), probably because they are thought to be the most effective. The questions that remain unanswered are: are they really more effective or rather more promoted by the media? And are they cheaper than others?
Our investigation also showed that younger supplement users did not habitually add multivitamin or minerals to their protein supplements. This finding is in accordance with previous studies [20, 30].
In terms of source of information, we found that a high proportion of the subjects (34.0%) relied on the instructor. This was slightly lower than the rate found by Morrison et al.  amongst the American sample (38.7%), while Goston and Correia  reported only 14.1% of the users in Brazil relying on the gym instructors' guidelines. In this study, only few persons indicated consulting a physician for supplementation prescription (13.0%), a similar rate was reported by Goston and Correia  (14.6%), however, those rates were quite different to that reported by Morrison et al. . In our sample of Italian fitness centers users, "word to mouth" was found to represent 16.0% of the information sources of supplementation, whilst Goston and Correia  reported 9.9% and Morrison et al.  63.1%. It is important to underline that no one indicated consulting a nutritionist, whereas in Morrison et al'  and Goston and Correia' studies  the relative proportion is as high as 30.0%. It is clear that more studies are necessary to better understand this phenomenon.
In agreement with Goston and Correia , we found that users consumed more high protein food than non-users, in particular meat, but less snacks and bakery products than non-users. In addition, the use of supplements appears to be associated with persons who have already healthier dietary habits . The sample size could be considered a limit of the study but considering strength and conditioning adepts only, most of the studies we found reported similar sample size [20, 30]. This might be related to the difficulties to deal with managers and fitness adepts. In order to overcome these difficulties and to increase the sample a project named PP (Protein Project) is currently involving three European universities and the Italian National Olympic Committee (CONI). The results of this study will hopefully be published in future manuscripts and complete the current investigation.