Does vitamin D improve athletic performance?
Weak EvidenceIT DEPENDS
Weak evidence links vitamin D supplementation to athletic performance improvements. Correcting deficiency may restore baseline function, but supplementation above adequate levels does not enhance performance in vitamin D-sufficient athletes.
The Verdict
Weak evidence links vitamin D supplementation to athletic performance improvements. Correcting deficiency may restore baseline function, but supplementation above adequate levels does not enhance performance in vitamin D-sufficient athletes.
What the Evidence Shows
Vitamin D receptors are present in skeletal muscle, leading to hypotheses that adequate levels support muscle function, power output, and recovery. Observational studies find correlations between higher vitamin D status and better athletic performance, but these likely reflect confounding by outdoor training exposure and overall health behaviors. Intervention trials show a clear pattern: athletes who are deficient (below 30 nmol/L) and supplement to adequate levels show genuine improvements in muscle strength and power. However, athletes already at sufficient levels (above 75 nmol/L) show no additional performance benefits from supplementation, even to supraphysiological levels. A meta-analysis of 13 RCTs in athletes found no significant overall effect on strength, power, or VO2max, though subgroup analysis of deficient populations showed moderate improvements. The widespread vitamin D insufficiency in indoor athletes and those at northern latitudes (40-70% prevalence) means correction of deficiency has legitimate performance implications. However, this represents restoration of normal function rather than performance enhancement. Claims of supra-physiological benefits are not supported. Additionally, vitamin D's role in bone health, immune function, and injury recovery may indirectly support athletic performance by reducing training interruptions.
Evidence Quality
2
Meta-Analyses
8
RCTs
5
Observational
Important Caveats
- ⚠️ Benefits are limited to correcting deficiency, not enhancing beyond sufficiency
- ⚠️ Observational associations are heavily confounded by sun exposure and fitness level
- ⚠️ Optimal athletic performance threshold remains debated (75 vs 100 nmol/L)
- ⚠️ Supraphysiological dosing carries hypercalcemia risk without additional benefit
Population Studied
Competitive and recreational athletes across multiple sports; ages 18-40, including indoor athletes and those at northern latitudes
Dosage
Studies used 1000-5000 IU per day or 50,000 IU weekly; doses depend on baseline status and target serum level of 75-100 nmol/L
Duration
Serum levels reach steady state after 8-12 weeks of supplementation; performance studies lasted 6-16 weeks
Supporting Studies (2)
Effect of vitamin D supplementation on muscle strength: a systematic review and meta-analysis
Meta-AnalysisTomlinson PB, Joseph C, Angioi M. · Journal of Science and Medicine in Sport (2015)
Meta-analysis found vitamin D supplementation significantly improved upper and lower limb muscle strength in vitamin D-deficient adults, with greater effects in those with baseline levels below 30 nmol/L.
View paper (DOI) →Vitamin D supplementation and physical performance in adolescent swimmers
RCTJastrzebska M, Kaczmarczyk M, Suarez AD, et al. · Journal of Strength and Conditioning Research (2016)
Adolescent swimmers supplementing with 6000 IU/day for 8 weeks showed significant improvements in sprint performance and peak power output compared to placebo, coinciding with correction of baseline insufficiency.
View paper (DOI) →Contradicting Studies (1)
Vitamin D supplementation and athletic performance in vitamin D-sufficient athletes: a systematic review with meta-analysis
Meta-AnalysisFarrokhyar F, Sivakumar GK, Englesbe K, et al. · British Journal of Sports Medicine (2017)
In athletes with baseline vitamin D levels above 75 nmol/L, supplementation had no effect on VO2max, vertical jump, sprint time, or muscle strength across 13 RCTs regardless of dose used.
Why this disagrees:
When baseline deficiency is absent, vitamin D supplementation provides no ergogenic benefit. The performance improvements seen in some studies reflect restoration of normal muscle function from deficiency rather than genuine performance enhancement above physiological norms.