Calcium
Calcium is the most abundant mineral in the body — 99% is stored in bone and teeth, the remaining 1% is critical for muscle contraction, nerve signalling, blood clotting, and enzyme activation. It cannot function without vitamin D, which enables intestinal absorption.
Daily requirements
- Ages 19–50: 1,000 mg/day.
- Women 51+ and men 71+: 1,200 mg/day.
- Pregnancy / lactation: 1,000–1,300 mg (depending on age).
- Tolerable Upper Intake Level: 2,000–2,500 mg/day (depending on age).
Food-first approach
Dietary calcium is safer and more effective than supplements. Population studies suggest calcium supplements above ~500 mg per dose may modestly increase cardiovascular risk (Bolland 2010; disputed by other analyses), while dietary calcium does not. Aim to meet the RDA from food; use supplements only to fill gaps.
Best food sources
- Plain yogurt (1 cup): 300–450 mg
- Milk (1 cup): 300 mg
- Fortified plant milks: 300 mg
- Cheese, cheddar (1.5 oz): 300 mg
- Sardines with bones (3 oz): 325 mg
- Tofu, calcium-set (½ cup): 250 mg
- Kale (1 cup cooked): 245 mg
- Collard greens (1 cup cooked): 268 mg
- Almonds (1 oz): 76 mg
Carbonate vs citrate
- Calcium carbonate — 40% elemental calcium; cheapest; requires stomach acid so take with meals. Common in Tums, generic supplements.
- Calcium citrate — 21% elemental; absorbed with or without acid; preferred if you take a PPI or have atrophic gastritis.
- Split doses: maximum single-dose absorption plateaus at ~500 mg elemental. If you need 1,000 mg from supplements, split into two doses.
- Don't take with iron: calcium blocks iron absorption. Separate by 2+ hours.
Calcium and vitamin D — the paired story
Without adequate vitamin D, only 10–15% of dietary calcium is absorbed. With sufficient vitamin D (25(OH)D ≥ 30 ng/mL), absorption rises to 30–40%. Osteoporosis and fracture- prevention trials that use both calcium and vitamin D produce larger effects than either alone. See our osteoporosis page.
Kidney stones
Counterintuitively, higher dietary calcium reduces kidney stone risk (by binding dietary oxalate in the gut). Calcium supplements may modestly increase risk, especially if taken between meals. If you're prone to calcium-oxalate stones, prioritise food calcium consumed with oxalate-containing meals and stay well hydrated.