Vitamin D and Athletic Performance
Vitamin D is one of the most-discussed nutritional considerations in sports medicine. The evidence is clear: correcting deficiency in deficient athletes helps performance modestly; supplementation of already-sufficient athletes provides no ergogenic benefit.
Performance-relevant biology
- Skeletal muscle — vitamin D receptors in fast-twitch fibres; deficiency causes proximal myopathy, reduced strength and power.
- Bone — stress-fracture prevention in high-impact sports.
- Immune — reduces respiratory infection rates that disrupt training.
- Testosterone — modest effect in deficient men; see testosterone page.
- Cardiac — VO₂max may improve modestly with correction of deficiency.
The performance meta-analysis
Farrokhyar 2017 pooled 13 trials in athletes and physically active adults: vitamin D supplementation modestly improved muscle strength (grip, jump) and power, with larger effect in those starting deficient. No consistent improvement in endurance metrics in already-sufficient athletes.
Screening protocols
- Elite and competitive athletes at latitudes > 35°: pre-season and mid-winter 25(OH)D testing.
- Indoor-sport athletes (gymnastics, basketball, ice hockey, dance): screen year-round.
- Athletes with stress-fracture history or recurrent injury: annual screening minimum.
- Target 25(OH)D 40-50 ng/mL — higher than general-population sufficiency, common in sports-medicine practice.
Dosing for athletes
- Deficient (< 30 ng/mL): 4,000-5,000 IU/day cholecalciferol for 8-12 weeks, then re-test and adjust.
- Insufficient (30-40 ng/mL): 2,000-4,000 IU/day for correction, then 2,000 IU/day maintenance.
- Sufficient (> 40 ng/mL): 1,000-2,000 IU/day maintenance year-round.
- Take with a fat-containing meal for best absorption.
Anti-doping status
Vitamin D is not on the WADA banned list. All cholecalciferol supplements are compatible with competition anti-doping rules. Use products with Informed-Sport or NSF Certified for Sport labels for guaranteed batch testing against banned-substance contamination.