Longitudinal Changes in Vitamin D and Body Composition in NCAA D1 Male Basketball Players

Abstract

Quantification of body composition changes with seasonal Vitamin D changes is not well-described. PURPOSE: To: 1) assess longitudinal changes in total body fat, lean, and bone tissue mass over 10-months and 2) explore relationships between Vitamin D, body composition, diet and sun exposure. METHODS: Male collegiate basketball players underwent dual energy x-ray absorptiometry (DXA) scans on four occasions: December 2016 (Start); April 2017 (End); July 2017 (Start Weights); October 2017 (End Weights) to quantify total body fat, lean, and bone mass. Blood was collected on 3 occasions (End; Start Weights; End Weights) and analyzed for serum 25-hydroxy vitamin D (25-OH- D). Food frequency questionnaires completed twice (Start and End Weights) with subjective reporting of sun exposure throughout weight-training. RESULTS: 11 (7 African- American) completed testing (age 20±1years; BMI 24.0±1.7kg/m2). Non-significant (NS) changes noted in total body fat percentage, which was lowest at End (16.1±2.1; 15.5±1.8; 16.6±2.2; 15.8±2.0%) and lean mass which was highest at End Weights (70.4±9.5; 71.4±9.1; 70.8±9.1; 74.3±9.3kg) while bone mineral density (BMD) increased steadily over time (1.33±0.10; 1.34±0.13; 1.35±0.12; 1.36±0.12g/cm2); (Start; End; Start Weights; End Weights, respectively). Serum 25-OH-D levels were deficient (<20ng/ mL) at End (18.9±7.3ng/mL) but replete at Start Weights (32.2±12.8ng/mL) and End Weights (32.2±7.7ng/mL). African-American players spent less hours per week in the sun vs Caucasian players (6.5±2.3 vs. 11.2±3.7 hours/week; p=0.02) and ingested less Vitamin D in their diet (135.9±58.6 vs. 207.0±70.4; p=0.10)(African-American vs. Caucasian, respectively). Start Weight serum 25-OH-D levels significantly associated with: End Weight minus Start Weight (Δ) total fat mass (r=0.69;p=0.02), dietary sodium intake (r=0.65;p=0.04), and dietary iron intake (r=0.89;p=0.001). CONCLUSION: Collegiate male basketball players living in the Midwest (latitude 42°) demonstrate serum 25-OH- D deficiency at the end of the competitive season, but are replete (>30ng/mL) during summer training. Mild (NS) fluctuations in body composition occurred, with increased fat while detraining and increased lean mass with strength training. BMD increased despite seasonal variation in serum 25-OH-D.