Dietary fiber and saturated fat are linked to bone mineral density in amenorrheic athletes
Barron, Elizabeth M.
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The Female Athlete Triad, consisting of the interrelated conditions of low energy availability, leading to menstrual disturbances and low bone mineral density, is commonly diagnosed amongst excessively exercising women. The American College of Sports Medicine emphasizes that the underlying factor of the Triad is a discrepancy between dietary energy intake and the energy requirements needed to support high levels of physical activity in addition to other homeostatic and physiological bodily processes. Although low energy availability is largely recognized as a causative factor for amenorrhea and low bone density, no studies to date have examined specific macro- and micro-nutrient intake relating to bone mineral density in the female athlete population. The hypothesis to be tested was that a difference in the intake of specific nutrients between athletes with menstrual disturbances (amenorrheic) and regularly menstruating (eumenorrheic) athletes contributes to low bone mineral density in female athletes exhibiting symptoms of the Triad. Methods: 4-day food records were collected from 118 females, ages 14-23 years, who exhibited weight within the normal range. 68 participants were amenorrheic athletes (AA), 24 participants were eumenorrheic athletes (EUM), and 26 participants were non-exercising females within the same age group (non-athletes: NA). Serum levels of vitamin D, phosphorus, calcium, and estradiol were also collected. Results: In contrast to previous studies, there was no difference in energy availability between the AA, EUM, and NA groups. The groups did differ in their intake of several macro-and micro-nutrients, and many of these nutrients correlated significantly with lumbar spine BMD. In a multivariate model that included vegetable and total proteins, soluble, insoluble and total dietary fiber, pectins, phytic acid, natural folate, calcium intake, vitamin D intake, serum vitamin D levels, and % calories from saturated fatty acids (SFA), only dietary fiber remained negatively associated and % calories from SFA positively associated with lumbar spine BMD. Conclusions: Dietary fiber has a significant inverse association and % calories from SFA a positive association with lumbar spine BMD, even after controlling for other nutrient intake and serum levels and intake of Vitamin D and calcium. Therefore, fiber and saturated fat may exert effects unrelated to vitamin D status and overall energy availability to impact bone density. Nutrition guidelines for female athlete triad patients need to be reassessed.