Effects of energy availability and dietary macronutrients on bone mineral density in male and female vocational ballet dancers

INTRODUCTION: Adequate Energy Availability (EA) is crucial to support physiological functions, optimal performance and bone mineral density (BMD). Young ballet dancers following a high-volume of training are predisposed to low EA due to high Energy Expenditure (EE) and insufficient Energy Intake (EI) to match this balance. This study aimed to examine the relationship between EA, dietary macronutrients and BMD in vocational ballet dancers.
METHODS: BMD and body composition of 25 dancers (female n=15, male n=10) were measured via DEXA. Three-day EA was calculated by subtracting EE (measured using continuous heart rate monitoring – Polar M430) from EI (dietary diary). Macronutrients (Carbohydrates, Protein, Fat) were analysed using Nutritics Software. Menstrual status was evaluated through questionnaires.
RESULTS: Low EA (<30kcal/kgFFM/day) was found in 88% of ballet dancers (12 female, 10 male) (3.9±22.7 kcal/FFM/ day). There were significant differences between female and male in lumbar spine (LS) BMD Z-score (female -1.1±0.7; male 0.29±0.7), EA (female 15.7±31.0 kcal/FFM/ day; male -13.7±11.3 kcal/FFM/ day) and EE (female 1386±540.6 kcal; male 3026±279.4 kcal). There was moderate-negative correlation between EA and BMD Z-score LS (r=-0.581; p=0.002) and strong-positive correlation between EE and BMD Z-score LS (r=0.727; p<0.001). No significant correlations between EA and menstrual status were found. Moreover, 88% of the ballet dancers did not meet the American College of Sports Medicine recommendations for carbohydrates (3.20±0.58 vs 6-10 g/kg/ day) and 32% for protein intake (0.99±0.13 vs 1.2-1.7 g/kg/ day).
DISCUSSION: Modern literature describes Relative Energy Deficiency in Sport (RED-S) in female and male athletes performing high volumes of training. Our study also found that most of the dancers, female and male, did not meet the recommendations for EA, carbohydrates and proteins intake. However, low EA did not seem to have a negative effect on BMD or menstrual status, as seen in other studies. Higher EE seemed to correlate with higher BMD, possibly explained by the larger EE in those with more FFM, which also had a positive correlation with BMD. Unfortunately, few limitations were found including the self-reported nutritional diaries and the cross-sectional nature of the study to assess BMD.