Calcium
Helps keep bones strong; prevents or slows osteoporosis.
People over 50 may need supplements if they don't get 1,200 milligrams a day from food. Younger people need at least 1,000 milligrams a day (about three servings of milk, yogurt, or cheese). Calcium should also come from dietary sources, such as nonfat or low-fat milk, dairy products, and some leafy greens.
Choosing a calcium supplement can be confusing. There are different forms of calcium (such as carbonate or citrate) and various types of products (pills, liquids, powders, even candies). A dose may be two pills a day, or as many as 16. Some supplements contain other ingredients as well. Here’s what you need to know.
Why do I need calcium?
Calcium is vital for bone health. It’s also needed for many other bodily functions, such as regulating heartbeats, conducting nerve impulses, making muscles contract, and helping blood clot. The daily recommendation is 1,000 milligrams for adults up to age 50; 1,200 milligrams for ages 51 and older.
How do I know if I need a calcium supplement?
That depends on your diet. Dairy foods provide the most calcium. Fish with bones (like sardines and canned salmon) and dark leafy greens contain respectable amounts; broccoli, almonds, and figs provide calcium, too. And there are many calcium-fortified products, such as some orange juice, soy milk, tofu, and cereals. If you don’t eat these foods often, you should consider a supplement.
What’s the difference between the forms of calcium?
Calcium occurs naturally bound to other substances—such as carbonate, citrate, or gluconate—never alone. Each form contains a different percentage of “elemental” calcium. Calcium carbonate contains the most calcium by weight—40%. The more calcium, the fewer pills you need. Supplement labels list calcium and what percent of the Daily Value (1,000 milligrams) a dose provides.
Are some forms of calcium better?
Not from a practical standpoint. Some studies have found that calcium citrate is best absorbed. But focus on getting enough calcium, rather than what form it comes in. Calcium carbonate is a good choice because it is cheapest and you need to take only two or three pills a day (though it may make you gassy or constipated). Don’t fall for claims that coral calcium—derived from the “remnants” of living sea coral—is better absorbed. It won’t cure allergies, multiple sclerosis, or other diseases, as is often claimed, and it’s expensive.
How should I take my calcium?
In doses of no more than 500 milligrams at a time. The body absorbs larger amounts less efficiently. If possible, take calcium carbonate with meals, since stomach acid secreted during digestion helps enhance its absorption. Calcium citrate is well absorbed without stomach acid, so you can take it anytime. This is a plus for people who produce low levels of acid—a condition called achlorhydria, which worsens with age.
How much is too much?
Don’t exceed 2,500 milligrams of calcium a day, since that can increase the risk of certain kinds of kidney stones. If you’re prone to kidney stones, check with your doctor before taking calcium. Depending on the type of stones you form, calcium may either decrease or increase the risk. If you eat a lot of calcium-fortified foods, along with milk and other dairy foods, and also take a supplement, you may be getting too much.
Does fiber interfere with calcium absorption? What about oxalates in spinach and other foods?
Some kinds of fiber do reduce calcium absorption somewhat. If your breakfast cereal is high in wheat bran, for instance, take your calcium pill at lunch. Fiber from oats and other grains (including standard doses of psyllium, such as Metamucil) doesn’t appear to be a problem. Oxalates, substances found in many plant foods (especially some leafy greens, like spinach), bind to calcium and thus reduce its absorption. But because foods high in oxalates tend to be rich in calcium, some of the calcium is still absorbed. If you get the recommended daily amounts of calcium from a variety of sources, such dietary interactions shouldn’t be a problem.
Are calcium supplements safe?
Calcium carbonate from dolomite, bone meal, oyster shells, or coral can contain lead and other toxic metals, but levels have declined over the years. Of 32 calcium products recently tested by ConsumerLab.com, only one failed because of too much lead.
What else should I look for in my supplement?
Calcium absorption requires vitamin D. There’s growing evidence that the more vitamin D you get, the less calcium you need, and that if you don’t get enough D, calcium provides much less benefit. If you don’t take a multivitamin/mineral pill (which always contains D), take a calcium supplement that provides the vitamin. You don’t need to take calcium and D at the same time, but it can be convenient if your supplement contains both.
What to do
• Get as much calcium as you can from foods, which contain other nutrients that also boost bone health. Make up for shortfalls with calcium supplements. (See below for a list of calcium-rich foods, and see “The Good-for-Your-Bones Diet.”)
• Take whatever supplement is most convenient and cheapest (usually calcium carbonate, found in many over-the-counter antacids). And keep taking it. If you stop you lose the benefit. Pills, chewables, powders, and liquids are all acceptable.
• Take calcium with meals to enhance absorption (not necessary with calcium citrate), but no more than 500 milligrams at a time.
• Get at least 200 IU of vitamin D a day if you’re under 50; 400 IU if you’re 50 to 70; 800 to 1,000 IU if you’re over 70.
• Check with your doctor or pharmacist if you take thyroid hormones, corticosteroids, tetracycline, or iron pills. Calcium can interfere with these and some other drugs and minerals. H-2 blockers (such as Zantac or Pepcid) and proton pump inhibitors (such as Nexium or Prilosec) can decrease calcium absorption. You may need to take them at different times.
• Don’t forget daily weight-bearing exercise, which is essential for strong bones.
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