Vitamin D and football: higher blood levels, no demonstrated performance gain

Nine studies, several aspects of performance

The researchers brought together eleven publications covering nine independent studies, involving 312 players. Eligible studies compared vitamin D supplementation with a control condition. The main analyses were based solely on randomized trials.

The review examined blood concentrations of 25-hydroxyvitamin D, or 25(OH)D, along with jumping, sprinting, aerobic capacity and muscular performance. The available abstract does not detail the doses, durations or control conditions for each study.

The blood marker rises, but performance gains remain unclear

In the pooled analyses of randomized trials, supplementation was associated with higher blood concentrations of 25(OH)D. This finding concerns vitamin D status, not directly the ability to play better.

For jumping, sprinting, aerobic capacity and muscular performance, none of the pooled effects were statistically significant. However, the estimates remain uncertain: these findings do not demonstrate that any benefit is impossible.

This distinction matters when assessing a sports supplement claim. An improvement in the biological marker measured is not enough to establish an improvement in the physical abilities needed on the pitch.

Evidence too uncertain to promise a sporting benefit

The authors rate the certainty of the evidence as low for blood vitamin D levels, jumping and muscular performance. It is very low for sprinting and aerobic capacity. They call for larger, better-designed randomized trials using standardized tests relevant to football.

The abstract does not establish whether the results differ according to baseline vitamin D status. It therefore does not support a specific conclusion for players who were initially deficient, or allow these observations to be generalized to all athletes.

What we can take away

This review does not provide sufficiently robust evidence to present vitamin D as a supplement that improves football performance. It distinguishes higher blood levels from a demonstrated sporting benefit.