The researchers randomized 30 UK-based athletes and 30 age-matched healthy non-athletes into two groups, a vitamin D group (5,000 IU/day) and placebo. They assessed vitamin D status in both groups before supplementation.
The authors found that 62% of the athletes and 73% of the controls had vitamin D blood levels < 20 ng/mL. After supplementation, vitamin D status increased significantly from baseline mean 11 ng/mL to 41 ng/mL in the vitamin D group, with no significant change in the placebo group.
The vitamin D group demonstrated a significant increase in 10 meter sprint times (P = 0.008) and vertical jump height (P=0.008), with no change among the placebo participants.
The authors call for future studies using larger sample sizes. They conclude:
“The current data supports previous findings that athletes living at Northerly latitudes (UK = 53° N) exhibit inadequate vitamin D concentrations. Additionally the data suggests that inadequate vitamin D concentration is detrimental to musculoskeletal performance in athletes.”
Dr Graeme L Close, lead author of the study said he and his team would like further research to investigate the optimum vitamin D dose for various tissues, providing evidence to encourage increasing the recommended daily allowance of D.
Source: Close GL, et al. Assessment of vitamin D concentration in non-supplemented professional athletes and healthy adults during the winter months in the UK: implications for skeletal muscle function. K Sports Sci. Oct 2012.