Vitamin D supplementation and body composition changes in collegiate basketball players: a 12-week randomized control trial

Abstract

Background: Vitamin D promotes bone and muscle growth in non-athletes, suggesting supplementation may be ergogenic in athletes. Our primary aim was to determine if modest Vitamin D supplementation augments favorable body composition changes (increased bone and lean mass and decreased fat mass) and performance in collegiate basketball players following 12 weeks of standardized training.

Methods: Members of a men's and women's NCAA D1 Basketball team were recruited. Volunteers were randomized to receive either a weekly 4000 IU Vitamin D₃ supplement (D3) or placebo (P) over 12 weeks of standardized pre-season strength training. Pre- and post-measurements included 1) serum 25-hydroxy vitamin D (25(OH)D); 2) body composition variables (total body lean, fat, and bone mass) using dual-energy X-ray absorptiometry (DXA) scans and 3) vertical jump test to assess peak power output. Dietary intake was assessed using Food Frequency questionnaires. Main outcome measures included changes (∆: post-intervention minus pre-intervention) in 25(OH)D, body composition, and performance.

Results: Eighteen of the 23 players completed the trial (8 females/10 males). Eight received the placebo (20 ± 1 years; 3 females) while ten received Vitamin D₃ (20 ± 2 years; 5 females). Weekly Vitamin D₃ supplementation induced non-significant increases (∆) in 25(OH)D (2.6 ± 7.2 vs. -3.5 ± 5.3 ng/mL; p = 0.06), total body bone mineral content (BMC) (73.1 ± 62.5 vs. 84.1 ± 46.5 g; p = 0.68), and total body lean mass (2803.9 ± 1655.4 vs. 4474.5 ± 11,389.8 g; p = 0.03), plus a non-significant change in body fat (-0.5 ± 0.8 vs. -1.1 ± 1.2%; p = 0.19) (Vitamin D₃ vs. placebo supplementation groups, respectively). Pre 25(OH)D correlated with both Δ total fat mass (g) (r = 0.65; p = 0.003) and Δ total body fat% (r = 0.56; p = 0.02). No differences were noted in peak power output ∆ between the D3 vs. P group (-127.4 ± 335.4 vs. 50.9 ± 9 W; NS). Participants in the D3 group ingested significantly fewer total calories (-526.2 ± 583.9 vs. -10.0 ± 400 kcals; p = 0.02) than participants in the P group.

Conclusions: Modest (~517 IU/day) Vitamin D₃ supplementation did not enhance favorable changes in total body composition or performance, over 3 months of training, in collegiate basketball players. Weight training provides a robust training stimulus for bone and lean mass accrual, which likely predominates over isolated supplement use with adequate caloric intakes.

Keywords: 25-hydroxyvitamin D; basketball; body composition; sweat sodium.

Figure 1.

Study participant enrollment and randomization into vitamin D3 and placebo supplementation groups.

Figure 2.

Vitamin D₃ and placebo supplement group comparisons over time (pre- to post-intervention) for 25(OH)D (2a), bone mineral density (BMD)(2b), total body fat percent (2c), and total body lean mass (2d).

Figure 3.

Relationships between total dietary vitamin D₃ intake vs. 25(OH)D (3a; pre- and post-intervention); 25(OH)D vs. the change (Δ) in fat mass (3b; pre- and post-intervention); and the change (Δ) in 25(OH)D vs. pre-intervention 25(OH)D levels (3c; randomized into the placebo or vitamin D₃ supplement group). All change (Δ) values represent post-intervention minus pre-intervention.

Figure 4.

Relationships between total body bone mineral density (BMD) vs. sweat [Na⁺] (a), total dietary sodium intake (b), and total dietary calcium intake (c), and between sweat [Na⁺] vs. total dietary sodium intake (d) obtained at pre-intervention (baseline) testing.