Bailey Drewes '14
Nutritional Intake, Menstrual Function, and Serum Osteoprotegerin in Female Collegiate Cross-Country Runners
Approximately 44-46% of female distance runners demonstrate menstrual dysfunction versus 2-5% of the general population. Menstrual dysfunction can lead to the loss of bone mineral density and increased risk for stress fractures. Low energy availability predisposes female distance runners to the development of menstrual dysfunction (De Souza 2004). Thirty calories per kilogram of lean body mass (cals/kgLBM) is the lower limit of energy intake required to maintain normal menstrual function.
Purpose: To determine whether menstrual status changes as a response to energy availability, and whether serum osteoprotegerin (OPG; a marker of bone turnover) levels reflect changes in these two variables.
Methods: Subjects were recruited from a collegiate cross-country team. IRB approval and informed consents were obtained. Subjects completed a bone and menstrual health history survey at the beginning of the study. Subjects recorded weekly exercise totals and menstruation frequency over a three-month time period. Three-day diet records and serum samples were collected during early, peak, and late season. Serum 25-OH vitamin D was measured during late-season. ELISA assays were used to measure serum 25-OH vitamin D and OPG. Data was analyzed using multi-variable analysis of variance.
Results: Two subjects were amenorrheic coming into the study and 6 subjects were oligomenorrheic. No changes in menstrual status occurred during the course of the study. There were no correlations between energy availability, menstrual status and serum OPG levels. The average cals/kgLBM was 52.7 and the lowest reported cal/kg LBM was 31.7. Twenty subjects consumed less than the recommended 15 µg of vitamin D per day and 21 subjects consumed less than the recommended 1,500 mg of calcium per day at all three points during the season. Vitamin D deficiency (<75 nmol/L) was observed in 26 subjects.
Conclusions: Serum OPG and menstrual status do not appear to correlate with energy availability in this study. Energy availability may have been sufficient to prevent changes in menstrual status or OPG in this population. Inadequate dietary vitamin D and calcium intake was 64.5% and 67.7% respectively among the subjects. Female cross-country runners should be encouraged to increase their vitamin D and calcium intake to preserve bone mineral intensity.
Bailey Drewes presenting her research at the Northland Chapter of the American College of Sports Medicine, March 28, 2014.
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