Should athletes supplement vitamin D for performance?
Supplement if you are deficient or at clear risk of it. If your level is already adequate, extra vitamin D has not reliably improved strength, power, or endurance.
Vitamin D is essential for bone and muscle function, and low blood levels are common in athletes who train indoors, live far from the equator, cover most of their skin, or get little dietary vitamin D. Deficiency is a real health problem. That does not make vitamin D a universal performance supplement.
Randomized trials in athletes repeatedly show the same split: supplements raise blood vitamin D reliably, but strength and power do not reliably follow. The 2023 meta-analysis of eleven trials found no statistically significant improvement in upper-body strength, lower-body strength, or power. Earlier pooled work reached the same conclusion. Reviews that report promising performance signals also describe inconsistent results, small samples, and the likelihood that baseline status matters.
Correct a deficiency, not a number on a label
Vitamin D behaves more like a missing nutrient than an ergogenic drug. If you are deficient, correcting it supports normal bone and muscle biology and may matter for general health. If you are already sufficient, pushing the level higher has no dependable training payoff.
A blood 25-hydroxyvitamin D test is more informative than guessing. Testing is especially reasonable after repeated low results, limited sun exposure, bone-stress injury, malabsorption, or clinician concern. Dose should follow the result and medical context. Large intermittent “megadoses” are not automatically better, and chronic excessive intake can raise calcium to dangerous levels.
The evidence for preventing ordinary respiratory infections has also become less impressive as larger trials arrived, so “immune support” is not a reason to take unlimited vitamin D.
The takeaway
Treat vitamin D as nutrition insurance for a documented gap. Get sensible sun exposure where appropriate, eat vitamin-D-containing foods, and test when risk is meaningful. For an athlete with adequate status, another capsule is unlikely to add kilos to the bar or seconds to the clock.