Fracture studies often target 1,000–1,200 mg/day total intake in postmenopausal women for 1–3 years; vitamin D status matters
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Calcium
Provides bone and tooth structure and enables muscle contraction and nerve signaling.
Established functions
- Provides bone and tooth structure and enables muscle contraction and nerve signaling.
Dietary sources
- milk
- small fish eaten with bones
- firm tofu
Claims and evidence
Claims that Calcium alone prevents or treats disease, or invariably improves health without deficiency, are unsupported.
Japanese reference amounts
- Japanese adults (age and sex as specified): Adult men 700–800 mg/day; women 650 mg/day (RDA)
Amounts studied
- Fracture studies often target 1,000–1,200 mg/day total intake in postmenopausal women for 1–3 years; vitamin D status matters
Tolerable upper limits
- Adults: 2,500 mg/day
Forms and bioavailability
Supplement forms: calcium carbonate, calcium citrate
- Take carbonate with food; citrate is less acid-dependent; divide doses to 500 mg or less.
Safety and interactions
Adverse effects
- constipation
- stones
- hypercalcemia
Medicine and nutrient interactions
- levothyroxine, bisphosphonates, iron, quinolones
Contraindications and cautions
- Seek care before supplementing with hypercalcemia or kidney stones.
Practical selection
- Compare Calcium 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 mineral fact sheetsNIH Office of Dietary Supplements
Daiki Minaki (editorial and evidence review) ·