Vitamin D for Athletes
Skeletal muscle carries vitamin D receptors, and vitamin D affects fast-twitch fibre function, calcium handling, and post-exercise recovery. Deficiency is surprisingly common in elite athletes — particularly those in indoor sports (gymnastics, basketball, ice hockey, dance) and those with darker skin training at high latitudes.
Deficiency prevalence
Screening studies of Division I US college athletes report 30–70% deficient (< 30 ng/mL) depending on sport and latitude. NBA players (indoor sport, mostly Black athletes) had 32% severely deficient (< 20 ng/mL) and 47% insufficient (20–32 ng/mL) in a 2015 study. European football (soccer) squads show similar winter deficiency rates.
Performance evidence
- Muscle strength — meta-analyses show correcting deficiency modestly improves grip strength, jump height, and sprint performance. Effect largest in most-deficient athletes.
- VO2max — mixed evidence; small trials suggest improved aerobic capacity when starting deficient.
- Recovery — vitamin D reduces exercise-induced muscle damage markers (CK, myoglobin) in some studies.
- Sufficient athletes — supplementation beyond 30–40 ng/mL doesn't enhance performance further. There's no ergogenic effect in already-replete athletes.
Stress fractures
A landmark 2008 study of female Navy recruits found 800 IU vitamin D + 2,000 mg calcium daily reduced stress fracture incidence by 20% during 8 weeks of basic training. Similar signals exist in ballet dancers and runners. Screen and correct any athlete presenting with stress fracture.
Practical protocol
- Test 25(OH)D early season and mid-winter for all serious athletes at latitudes above 35°.
- Target 40–50 ng/mL (100–125 nmol/L) — the athletic target is often higher than the general-population sufficiency threshold.
- Deficient athletes: 4,000–5,000 IU/day cholecalciferol for 8–12 weeks, then re-test and titrate to 2,000 IU/day maintenance.
- Take with dietary fat (breakfast or main meal) for optimal absorption.
- Vitamin D is not on any anti-doping banned list — regular supplementation is compatible with WADA rules.