Vitamin D supplementation and exercise for improving physical function, body composition and metabolic health in overweight or obese older adults with vitamin D deficiency: a pilot randomized, double-blind, placebo-controlled trial

Purpose Vitamin D supplementation may have non-skeletal health benefits and enhance exercise responsiveness, particularly in those with low vitamin D levels. We determined whether, compared with placebo, vitamin D supplementation taken prior to and during a 12-week exercise program improves physical function, body composition or metabolic health, in overweight and obese older adults with vitamin D deficiency. Methods Fifty overweight or obese older adults (mean +/- SD age: 60 +/- 6 years; BMI 30.6 +/- 5.7 kg/m(2)) with vitamin D deficiency (25-hydroxyvitamin D [25(OH)D] < 50 nmol/L) were recruited. Participants were randomly allocated to receive either vitamin D-3 (4000 IU/day) or matching placebo for 24 weeks. Between weeks 12 and 24, all participants completed multi-modal exercise three days per week while continuing with vitamin D/placebo. Mean changes in physical function (primary outcome: gait speed), body composition and biochemical parameters at weeks 12 and 24 were compared between groups. Results Vitamin D supplementation, with or without exercise, had no effect on gait speed. From baseline to week 12, vitamin D supplementation increased serum 25(OH)D levels (placebo: 2.5 +/- 14.7 nmol/L; treatment: 43.4 +/- 18.4 nmol/L; P < 0.001) and reduced stair climb times (placebo: 0.3 +/- 1.0 s; treatment: - 0.2 +/- 1.0 s; P = 0.046). From 12 to 24 weeks, vitamin D supplementation combined with exercise decreased waist circumference (placebo: 1.3 +/- 7.3 cm; treatment: - 3.0 +/- 6.1 cm; P = 0.02) and waist-to-hip ratio (placebo: 0.01 +/- 0.05; treatment: - 0.03 +/- 0.05; P = 0.01) relative to placebo. Vitamin D supplementation, with or without exercise, had no effect on other physical function, body composition or metabolic health outcomes. Conclusion Vitamin D supplementation had no effect on most physical function, body composition or metabolic health parameters when taken alone, or during exercise, in overweight or obese older adults with vitamin D deficiency. Vitamin D-related improvements in stair climb times and waist circumference suggest that future trials should explore the effects of vitamin D on muscle power, and its effects on body composition when combined with exercise, in populations with moderate or severe vitamin D deficiency.