Vitamin D B
Useful only in deficiency: it does not increase strength in those with adequate intake
Citable fact
«Vitamin D» — evidence level B. Dosage: 1000–2000 IU per day for maintenance. In confirmed deficiency, higher doses are prescribed by a doctor, guided by blood 25(OH)D. Source: PMID 27379960, permanent link to the source in the list below.
How it works
It regulates calcium metabolism and the expression of vitamin D receptors in muscle tissue, affecting contractile function and protein synthesis; in deficiency these processes are impaired.
Dosage and intake
1000–2000 IU per day for maintenance. In confirmed deficiency, higher doses are prescribed by a doctor, guided by blood 25(OH)D.
Daily with fat-containing food — absorption is higher that way. Large doses once a week are tolerated worse and give a less stable level.
Forms
Cholecalciferol (D3) and ergocalciferol (D2) have been studied. D3 raises 25(OH)D levels more effectively; data on injectable forms are limited.
What is confirmed
- Correcting deficiency increases muscle strength in people with initially low 25(OH)D
- Reduced risk of stress fractures with adequate status together with calcium
- In athletes with a normal level, supplementation gives no strength gains
- Possible reduction in the risk of upper respiratory tract infections in winter
Adverse effects and limitations
- Megadoses (above 4000 IU long-term) lead to hypercalcemia, nausea and kidney stones
- Feeling unwell and muscle pain in overdose are hard to distinguish from other causes
- Without a blood test it is easy to take an unnecessary supplement for years
Interactions
- Thiazide diuretics together with calcium increase the risk of hypercalcemia
- Orlistat and cholestyramine reduce the absorption of fat-soluble vitamins
- Anticonvulsants accelerate the breakdown of vitamin D
Who must not use it
- Under 18 years: Prophylactic doses by age; high doses only as prescribed by a doctor.
- Pregnancy and lactation: Usually 400–1000 IU per day as prescribed; high doses are not used without monitoring the level.
- hypercalcemia
- sarcoidosis
- urolithiasis
- kidney failure
Sources
- Effects of Vitamin D Supplementation on Muscle Strength in Athletes: A Systematic Review · Chiang CM, Ismaeel A, Griffis RB · Journal of strength and conditioning research, 2017 · PMID 27379960
- International society of sports nutrition position stand: nutritional concerns of the female athlete · Sims ST, Kerksick CM, Smith-Ryan AE · Journal of the International Society of Sports Nutrition, 2023 · PMID 37221858
- Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance · Thomas DT, Erdman KA, Burke LM · Journal of the Academy of Nutrition and Dietetics, 2016 · PMID 26920240
See also
Open in the app
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