Effects of dietary intervention in young female athletes with menstrual disorders

The strenuous physical activity of professional female athletes may generate serious health problems. It is estimated that between 16% [1] and 61% [2] of female athletes suffer from hypothalamic-pituitary menstrual disorders. In studies conducted by Torstveit et al. [3], the frequency of menstrual disorders among elite female athletes was 34.5% in aesthetic disciplines, 30.9% in endurance disciplines, 23.5% in weight class disciplines, 17.6% in anti-gravitation disciplines, 16.7% in technical disciplines, 12.8% in ball game and power sport disciplines.

There is a disturbingly low level of knowledge among athletes of different sports disciplines regarding the potential health effects of untreated menstrual dysfunctions [4, 5]. Young female athletes are not aware that a long-term negative energy balance, inadequate nutrient intake, and endocrine disorders including the hypothalamic-pituitary-ovarian axis are particularly dangerous in the period of achieving the peak bone mass and may contribute to metabolism disturbances in the skeletal tissue. Christo et al. [6] observed significantly lower BMD values in the lumbar spine area among athletes with menstrual disorders compared to physically active and sedentary women with regular cycles. The study of Nicolas et al. [7] also showed a significantly decreased bone density in athletes suffering from amenorrhea and oligomenorrhea. Studies of athletes with amenorrhea and low bone mass showed that even after the restoration of the menstrual cycle bone density remained significantly lower compared to the average value of women in this age group [8].

Prolonged menstrual disorders have a negative effect on the quality and quantity of plasma lipoproteins, which favors the formation of atherosclerotic lesions. Significant differences in blood lipid parameters in athletes with amenorrhea compared to athletes with regular cycles have been demonstrated. In the study of Rickenlund et al. [9], athletes with amenorrhea had significantly higher levels of total and LDL cholesterol compared to athletes and sedentary women with regular cycles. The increase in the LDL levels was higher when the energy intake was lower.

Taking the afore mentioned into account it seemed appropriate to take steps to limit menstrual disorders and their negative health effects. The aim of this study was to evaluate nonpharmacological dietary interventions on the menstrual disorders in young female athletes.

In the study, the authors evaluated the effects of an individualized dietary intervention, providing an appropriate energy availability, energy balance and an adequate intake of minerals and vitamins, on the menstrual cycle in young female athletes. Diets were planned by taking into account the total energy expenditure, nutritional status and the current training period, in the expectation that an individualized diet will help reduce menstrual dysfunctions without decreasing total energy expenditure, training volume and hormonal treatment. The planned study period was nine months, and this study provides results obtained after three months, the first time-point, post dietary intervention start.

Our results concerning energy and nutritional intakes, obtained before the start of the above dietary intervention, were similar to our previous results [18, 19]. They were also comparable to those obtained by Hoch et al. [20] and Tomten et al. [21], who also demonstrated energy availability below 30 kcal/kg FFM/d and the negative energy balance in athletes with menstrual disorders. Furthermore, similarly to studies by Manore [15], Hoogenboom et al. [22], Quah et al. [23] and Woolf et al. [24], daily diet values for most vitamins and minerals indicated deficiency. In study participants, the RMR was also lower than predicted value. Similar to Mallinson et al. [25], we used the RMR/pRMR ratio as an indicator of the energy status. The mean value obtained was 92.8 with a range of 72.3-115.5, potentially indicating an energy deficiency in some part of study participants. Many authors suggested that body weight alone and an intensive physical activity are not sufficient to explain the onset of menstrual disorders. Many authors suggested that menstrual dysfunction occurs only in the presence of relative caloric deficiency resulting from inadequate nutritional intake precluding achievement of an appropriate energy expenditure. They also emphasize that this is the most important factor leading to menstrual disorders development [26, 27]. Results presented by Thong et al. [28] also showed an inadequate energy intake among female athletes with amenorrhea. In the above case, energy availability was 50% lower compared to regularly menstruating women (16 kcal/d/kg FFM and 30 kcal/d/kg FFM, respectively). The relationship between normal functioning of the hypothalamic-pituitary-gonadal axis and an adequate energy intake under stress conditions was already demonstrated in the 1980s. In runners, Kaiserrauer et al. [29] showed that the use of a low-energy diet, deficient in protein and fat, may contribute to progesterone serum concentrations reduction and the luteal phase shortening.

In athletes’ daily diets, the control of energy and nutrients intakes demonstrate significant variations. Despite mean values showing an increase of energy and nutrients intakes, the high standard deviation indicates that not all study participants adhere to the recommendations of the dietary intervention. This situation demonstrates how difficult it is to implement an individual diet in this group of subjects. During a three-month dietary intervention, an increased energy availability in the studied athletes was also observed. Additionally, the energy availability exceeded the critical value of 30 kcal/kg FFM/d. In athletes with menstrual disorders, Nattiv et al. [10] and DeSouza [30] indicated that an increased energy availability, and not the weight gain alone, is the most important factor for the restoration of regular menstrual cycles. Loucks et al. [25] suggested that the pulsatile secretion of LH depends on the energy availability, which was also confirmed in this paper (significant relationship between LH and energy availability). In our paper, despite the fact that after three months of non-pharmacological dietary intervention none of study participants resumed regular menses, LH and LH to FSH ratio significantly increased. In athletes, a surprising lack of changes in body weight and composition may be explained by decreased level of baseline RMR resulting from the long-term energy deficiency. Moreover, diets implemented during this dietary intervention aimed to provide a sustainable energy balance, thus to avoid weight gain.

In athletes, Dueck et al. [31] and Kopp-Woodroffe et al. [32] demonstrated the resumption of menses after approximately 6 months and 9–12 weeks, respectively. Competitive athletes should be counseled that the sustained resumption of menses (involving regular menstrual cycles of 36 days or less occurring in the period of 3 months or more) may take longer than one year, when non-pharmacological therapy is implemented. Arends et al. [33] found that the restoration of regular menstrual cycles in female athletes is possible after increasing the energy value of daily meals contributing to body weight and BMI increase. In the group of 373 female athletes, after five-year non-pharmacological dietary therapy, regular menstrual periods returned in 17.6% subjects. Moreover, in this group, a significant increase in BMI, from 20.8 ± 0.5 kg/m² to 22.7 ± 0.6 kg/m² (p < 0.005), as well as in body weight, from 58.0 ± 2.0 kg to 63.3 ± 2.3 kg (p < 0.005), were also observed. However, no information on body composition of the athletes from the above group were obtained. Dueck et al. [31] showed LH pulsatility accompanied by the weight gain of approximately 3 kg and a 6% body fat increase. In contrast, Loucks et al. [34, 35] have suggested that body weight changes are not associated with menstrual disturbances in athletes, probably due to adaptive energy-conserving mechanisms development allowing for the maintenance of body weight despite poor energy availability. Mallinson et al. [25] compared and contrasted responses of two exercising women with amenorrhea of varying duration to an intervention of increased energy intake. This study was very similar to ours due to implementation of a non-pharmacological dietary intervention without reducing the energy expenditure or the intensity and volume of training. In the case study conducted by Mallinson et al. [25], resumption of menses occurred 23 and 74 days into the intervention for the women with short-term and long-term amenorrhea, respectively. Recovery of regular menses and onset of ovulation coincided closely with increases in energy intake, weight gain and improvements in the metabolic environment.

In female athletes, difficulties in the restoration of regular menstrual cycles may result from multiple overlapping causes of such disorders. Bruni et al. [36] reported that inadequate dietary habits, extensive physical activity and stress are key factors differentiating women with menstrual disorders. The above situation demonstrates that an eventual use of a homogenous treatment in the population of women with menstrual disturbances or amenorrhea is impossible. Potential factors affecting menstrual cycle include various genetic, neuroendocrine and metabolic aspects. It seems that in the specific population included in our studies, all above mentioned factors, predisposing to such disorders, are present. Nattiv et al. [10] and Manore et al. [15] emphasized that an appropriately balanced diet with reduced training volume and intensity is the only possible way to alleviate menstrual disorders in female athletes. The present study is valuable because it is based on an individual, non-pharmacological diet intervention taking into account everyday burden of an intense physical effort without reduction of intensity and volume of everyday activities, which could be, according to authors’ knowledge, a potential cause of subject’s withdrawal from the study. In case of female athletes aiming to achieve desired results, the limitation of training sessions intensity is potentially difficult to accept intervention, therefore it was not suggested to study participants.

This study has several limitations. Firstly, LH and FSH concentrations were assessed only once before the start of dietary intervention, and then after three months. We did not determinate the pulsatile nature of those hormones, thus an assessment of the presence of ovulatory cycles in menstruating women was impossible. Secondly, the body composition was determined using the electrical bioimpedance method, which potentially raises some controversies. However, DEXA method was not used due to young age of study participants, tests frequency, and potential adverse (UV) effects.

This report provides further support for the role of energy deficiency in menstrual disorders among young female athletes and the benefits of an adequate energy intake and energy availability on hormones concentration. Continuation controlled dietary intervention is needed to assess the extent to which long-term improvement in the nutritional status results in improvements in the hormonal status of female athletes, to an extent that would allow the regulation of the menstrual cyclity.