Deficient-adult studies often use D3 800–2,000 IU/day for 8–12 weeks; individualize to diagnosis and blood level
Reviewed · Published
Vitamin D
Regulates calcium absorption, bone mineralization, and muscle function.
Established functions
- Regulates calcium absorption, bone mineralization, and muscle function.
Dietary sources
- salmon
- dried shiitake
- egg yolk
Claims and evidence
Claims that Vitamin D alone prevents or treats disease, or invariably improves health without deficiency, are unsupported.
Japanese reference amounts
- Japanese adults (age and sex as specified): Adults: 9.0 µg/day (AI)
Amounts studied
- Deficient-adult studies often use D3 800–2,000 IU/day for 8–12 weeks; individualize to diagnosis and blood level
Tolerable upper limits
- Adults: 100 µg (4,000 IU)/day
Forms and bioavailability
Supplement forms: vitamin D3, vitamin D2
- Absorbed better with a fat-containing meal; D3 generally sustains blood levels longer than D2.
Safety and interactions
Adverse effects
- hypercalcemia
- nausea
- kidney injury
Medicine and nutrient interactions
- thiazides, digoxin, orlistat
Contraindications and cautions
- Hypercalcemia, granulomatous disease, or severe kidney disease requires medical supervision.
Practical selection
- Compare Vitamin D amount per serving, form, allergens, and batch testing; prefer a single-ingredient product suited to the intended use.
Sources and review
- Dietary Reference Intakes for Japanese (2025)Ministry of Health, Labour and Welfare (Japan)
- NIH ODS vitamin fact sheetsNIH Office of Dietary Supplements
Daiki Minaki (editorial and evidence review) ·