Calcium
How much calcium adults need, where to get it without dairy, and why vitamin D is part of the answer.
Last revised
The main mineral in bone and teeth, and essential to muscle contraction, nerve signaling and blood clotting. Bone acts as the body's reserve, so a sustained shortfall is drawn from the skeleton.
How much adults need
The Recommended Dietary Allowance is 1,000 mg a day for adults 19 to 50 and men 51 to 70, and 1,200 mg for women 51 and older and men over 70. Teens aged 9 to 18 need 1,300 mg, because peak bone mass is being built. The upper limit is 2,500 mg a day for adults up to 50 and 2,000 mg after 50, counting food and supplements together.
Where to get it
Dairy is the densest common source: an 8-ounce (240 ml) glass of milk provides about 300 mg, 8 ounces of plain low-fat yogurt over 400 mg, and 1.5 ounces of cheddar cheese about 300 mg. Without dairy: calcium-fortified plant milks and juices, tofu made with calcium sulfate, canned sardines and salmon eaten with the bones, kale, bok choy, and fortified cereals. Spinach contains calcium but binds it with oxalate, so very little is absorbed.
Vitamin D is half the story
Calcium absorption depends on vitamin D, which is why the two are discussed and often prescribed together. Meeting a calcium target while low in vitamin D achieves less than the number suggests. The vitamin D RDA, 15 mcg (600 IU) a day for most adults and 20 mcg (800 IU) over 70, applies here as elsewhere.
Supplements are not automatically better
Where intake from food is adequate, extra calcium from supplements has not been shown to add benefit and has been linked in some studies to kidney stones and, more controversially, to heart risk. Food first is the general advice, with supplements where intake is genuinely low or where a doctor recommends them. Calcium carbonate is best absorbed with food; calcium citrate can be taken with or without it.
At a glance
| Term | Detail |
|---|---|
| RDA, adults 19-50 | 1,000 mg a day |
| RDA, women 51+ and men 71+ | 1,200 mg a day |
| RDA, ages 9-18 | 1,300 mg a day |
| 8 oz (240 ml) milk | about 300 mg |
| 1.5 oz cheddar cheese | about 300 mg |
| Non-dairy sources | fortified plant milks, calcium-set tofu, canned fish with bones, kale |
| Poorly absorbed source | spinach, because of its oxalate content |
| Required for absorption | vitamin D |
When to get help
See your doctor if you have broken a bone from a minor fall, have lost height, or have several osteoporosis risk factors. Talk to your doctor before taking calcium supplements if you have had kidney stones, kidney disease, or a parathyroid disorder. Get medical advice for symptoms of high blood calcium: persistent thirst, frequent urination, nausea, constipation, bone pain and confusion. Call 911 for a fall with a suspected broken hip or a head injury.
Where this comes from
- NIH Office of Dietary Supplements - Calcium Fact Sheet for Health Professionals
- Bone Health & Osteoporosis Foundation - Calcium and Vitamin D
- Dietary Guidelines for Americans - Dietary Guidelines for Americans, 2020-2025
Medical disclaimer
This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to your doctor, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 911.