Most of us grew up hearing that milk builds strong bones. That is true as far as it goes, but bone health is a bigger story than one mineral or one drink. Calcium matters a great deal, especially as we age. So do vitamin D, protein and, perhaps most of all, regular exercise. And when it comes to calcium supplements, the latest evidence suggests a more careful approach than "take one just in case."
Why calcium matters
About 99 percent of the calcium in your body is in your bones and teeth. Your bones are living tissue, constantly being broken down and rebuilt. You build most of your bone mass by your late twenties. After that, the goal is to hold on to it. Women lose bone faster in the years after menopause, which is why osteoporosis is more common in older women.
Calcium also helps your muscles contract, your nerves send signals and your heart keep its rhythm. If you do not get enough from food, your body takes it from your bones.
How much you need
The U.S. Office of Dietary Supplements lists these daily amounts on its calcium fact sheet:
- Adults 19 to 50: 1,000 mg
- Men 51 to 70: 1,000 mg
- Women 51 and older: 1,200 mg
- Everyone 71 and older: 1,200 mg
- Teens 9 to 18: 1,300 mg
The upper limit is 2,500 mg a day for adults up to 50 and 2,000 mg after 50, from food and supplements combined.
Food first
Calcium from food is the best choice for most people. It comes packaged with other nutrients and is less likely to cause problems than supplements. Good sources include:
- Dairy: a cup of milk or yogurt has about 300 mg. An ounce and a half of cheddar has about the same.
- Fortified plant milks and juices: often 300 mg or more per cup. Shake the carton, because calcium settles.
- Canned salmon and sardines with bones: about 180 to 325 mg per serving.
- Tofu made with calcium sulfate: can provide 250 mg or more per half cup. Check the label.
- Leafy greens: kale, bok choy, collard and turnip greens. Spinach contains calcium, but it is poorly absorbed.
- Beans, almonds, figs and fortified cereals add smaller amounts.
Try tallying a typical day. Many people get more calcium from food than they think and need only a little top-up, if any.
Do you need a supplement?
A supplement may help if you do not eat dairy or fortified foods, are vegan, have lactose intolerance, are an older woman with low intake, or have osteoporosis and your doctor recommends it.
The U.S. Preventive Services Task Force has said there is not enough evidence that calcium and vitamin D supplements prevent fractures in healthy older adults living at home, and it recommended against low-dose combinations for this purpose in women after menopause. That does not mean calcium does not matter. It means that if you already get enough from food, adding a pill is unlikely to help. People with osteoporosis or low intake are a different story, and your doctor will advise you.
Choosing a calcium supplement
- Calcium carbonate is the cheapest and most common. It contains the most calcium per pill, but it needs stomach acid, so take it with food. It is also found in some antacids.
- Calcium citrate is absorbed well with or without food, and is better for people who take acid-reducing medicines or are over 50. It is bulkier, so you may need more pills.
Check the label for elemental calcium, which is the amount you actually get. See how to read a supplement label.
How to take it
- Take 500 mg or less at a time. Your body absorbs calcium best in smaller doses. If you need more, split it between meals.
- Keep it apart from iron and thyroid medicine, by about four hours for thyroid medicine. Calcium also reduces absorption of some antibiotics and osteoporosis drugs. See supplement and drug interactions.
- Watch for constipation and bloating, especially with carbonate. Drinking water, eating fiber and switching to citrate can help.
- Count your antacids. If you use calcium-based antacids often, they count toward your total. See antacids, kidneys and bone health.
Are calcium supplements risky?
Some studies have raised concerns that calcium supplements might increase the risk of heart problems. Others have found no link. The evidence is mixed. Calcium from food has not been linked to the same concern. Supplements can increase the risk of kidney stones in some people. These are good reasons to get most of your calcium from food, and to avoid taking more than you need.
Calcium cannot work alone
- Vitamin D helps you absorb calcium. See how much vitamin D should you take.
- Weight-bearing and strength exercise, like walking, stair climbing, dancing and lifting weights, signals your bones to stay strong. This may be the single most important habit.
- Protein supports bone and muscle, which protects against falls.
- Do not smoke, and limit alcohol. Both weaken bones.
- Prevent falls with good lighting, clear floors and balance exercises. See hip mobility exercises and stretches.
Ask about a bone density test
Women 65 and older, and younger women after menopause who have risk factors, should ask their doctor about a bone density scan. Men with risk factors may benefit too. The Bone Health and Osteoporosis Foundation and MedlinePlus have helpful information.
The bottom line
Aim to get most of your calcium from food. If you fall short, a modest supplement, taken in doses of 500 mg or less with food, can fill the gap. Pair it with vitamin D, regular exercise and enough protein. For more, see our calcium ingredient page and the bone health goal page.