Calcium
Calcium (Ca)
Minerals. Modern nutrition.
Also called Calcium carbonate, Calcium citrate, Dicalcium phosphate, Oyster shell calcium
Pinyin: gài
Spanish: Calcio
Blocks iron and some medicinesThe most common mineral in the body. It builds strong bones and teeth and helps muscles and nerves work.
Did you know? About 99 percent of the body's calcium is in bones and teeth. The body will pull calcium out of bone to keep blood levels steady, so bone loss can happen even when a blood test looks normal.
What it may help, and how strong the proof is
- Bones. Calcium is needed to build and keep bone. Adding calcium to vitamin D lowers fractures in some older adults, but the effect is modest. In people who already get enough, extra calcium has not shown added bone benefit.Good proof
- Heart health. Calcium pills were once thought to protect the heart. Large reviews have not shown a clear benefit, and some suggest a small rise in heart attack risk from pills, though the evidence is mixed.Not supported
Parts of the body
Traditional use
In East Asia, tofu set with calcium or magnesium salts has long been a main calcium source. In many coastal cultures, small fish eaten whole, bones and all, supplied calcium too.
How it is classified
How people take it
Adults ages 19 to 50 and men ages 51 to 70 need 1,000 mg a day (RDA). Women 51 and up, and men 71 and up, need 1,200 mg a day. The upper limit is 2,500 mg a day for ages 19 to 50 and 2,000 mg a day for ages 51 and up, from food and supplements combined. Calcium carbonate works best with food, and calcium citrate can be taken any time.
Food, tablet and capsule.
Where to get it
Good sources are milk, yogurt and hard cheeses such as Swiss and cheddar, fortified plant milks and orange juice, canned sardines and salmon with bones, tofu set with calcium salts, kale, bok choy, broccoli, collard greens, and almonds. Spinach and rhubarb are high in calcium, but their oxalate blocks much of it. Pills come as calcium carbonate, citrate, and oyster shell (also carbonate).
Be careful
Calcium from food is safe. Pills can cause constipation, gas and bloating. High doses can raise the risk of kidney stones in some people. Some bone meal and oyster shell products have been found to contain lead, so choose tested brands.
Avoid if: kidney stones; high blood calcium; sarcoidosis.
Mixing with other things
- Works well together
Vitamin D helps the gut absorb calcium, so the two are often taken together.
- Works well together
Vitamin K2 helps bone proteins bind calcium.
- Works well together
Calcium and magnesium work as partners in muscle and bone, so their balance matters.
- Works well together
Bone formation needs calcium, vitamin D and trace minerals such as manganese.
- Use caution
Calcium blocks iron absorption when taken at the same time. Take them at least two hours apart.
- Use cautionAntibiotics (doxycycline, Cipro and similar)
Calcium binds quinolone and tetracycline antibiotics and lowers how much the body absorbs. Take them 2 to 4 hours apart.
- Use cautionThyroid medicine (levothyroxine (Synthroid))
Calcium lowers absorption of levothyroxine. Take thyroid medicine on an empty stomach, and keep calcium at least 4 hours away.
- Use cautionWater pills (furosemide, hydrochlorothiazide)
Thiazide water pills lower calcium loss in urine, so calcium levels can rise with high-dose supplements.
- Worth knowing
Boron may help the body keep calcium. The evidence comes from small trials only.
- Worth knowing
Oxalates in spinach bind calcium and block some of its absorption.
Found in these formulas
Bone trio (Modern)
The honest take
Calcium is needed for bones, but most of the benefit comes from getting enough in food. Pills help people who do not get enough, and they do not guarantee bone health. Reviews of calcium pills in healthy people found no clear heart benefit, and some hint at more risk.