The recommended dietary allowance (RDA) for calcium is 1,000 mg per day for men and women ages 19-50. After age 50, women get bumped up to 1,200 mg per day. Although it is far and away better to get your nutrients through diet (see below for a list of superstar sources), many people find it difficult to consume that much every day. A supplement can help make up the difference. But which supplements are best?
Calcium Carbonate vs. Calcium Citrate
Studies indicate that both forms work well, so it’s up to you and your doctor to decide which you should take. Calcium carbonate is easy to find and inexpensive, but your body absorbs it best when you take it with food (it relies on stomach acid to break it down). Calcium citrate works equally well on a full or empty stomach, and it might be a better choice for people who don’t produce enough stomach acid or who take acid-reducing drugs. Also, look for a supplement that also includes vitamin D, which is critical for calcium absorption and a valuable nutrient in its own right.
How to Take Calcium Supplements
Your body can only absorb about 500 mg at a time. I recommend getting the rest of your calcium through diet, but if you need to supplement with more than that, spread out your doses. Plus, this reduces the likelihood that you’ll experience the gas, bloating, and constipation that can occur with higher doses (calcium carbonate may be more likely to cause these symptoms).
Pills, chews, and calcium-fortified foods and drinks all appear to work equally well.
Watch Out For…
Calcium supplements can interfere with the absorption of iron, so if you take an iron supplement, take your calcium at a different time.
High doses of supplemental calcium are linked to kidney stones, and possibly cardiovascular problems. All the more reason to get most of your calcium through diet! That said, there’s no need to go overboard with calcium-rich foods (especially dairy products) either—intakes greater than 1,500–2,000 mg per day may be linked to a higher risk of prostate cancer.
Calcium can interact with several medications; if you take any of these, talk to your doctor before supplementing with calcium: Bisphosphates (drugs for osteoporosis), antacids that contain aluminum, beta-blocker or calcium-channel blocker blood pressure drugs, bile acid sequestrants (cholesterol-lowering drugs), calcipotriene (a topical medication for psoriasis), digoxin or sotalol (Betapace) (to treat irregular heart rhythms), diuretics, antibiotics, and thyroid medications.
For more information on calcium and supplements, check out this fact sheet from the Office of Dietary Supplements at the National Institutes of Health.
Dietary Sources of Calcium*
Yogurt, plain, low fat, 8 ounces—415 mg
Yogurt, fruit, low fat, 8 ounces—338–384 mg
Orange juice, calcium-fortified, 6 ounces—375 mg
Mozzarella, part skim, 1.5 ounces—333 mg
Sardines, canned in oil, with bones, 3 ounces—325 mg
Cheddar cheese, 1.5 ounces—307 mg
Milk, nonfat, 8 ounces—299 mg
Soybeans (edamame), cooked, 1 cup—261 mg
Tofu, firm, made w/calcium sulfate, ½ cup—253 mg
Salmon, pink, canned, solids with bone, 3 ounces—181 mg
Tofu, soft, made with calcium sulfate, ½ cup—138 mg
Cottage cheese, 1% milk fat, 1 cup—138 mg
Frozen yogurt, vanilla, soft serve, ½ cup—103 mg
Ready-to-eat cereal, calcium-fortified, 1 cup—100–1,000 mg
Turnip greens, fresh, boiled, ½ cup—99 mg
Kale, fresh, cooked, 1 cup—94 mg
Sesame seeds, 1 tablespoon—88 mg
Ice cream, vanilla, ½ cup—84 mg
Soy, rice, or almond milk, calcium-fortified, 8 ounces—80–500 mg
Almonds, 1 ounce (23 almonds)—75 mg
Chinese cabbage/bok choi, raw, shredded, 1 cup—74 mg
Bread, white, 1 slice—73 mg
Navy beans or cannellini, cooked, ½ cup—60 mg
Figs, dried, ¼ cup—60 mg
Sour cream, reduced fat, 2 tablespoons—31 mg
Bread, whole-wheat, 1 slice—30 mg
Broccoli, raw, ½ cup—21 mg
*Note: Don’t rely solely on dairy products to get your calcium—a 2009 review of studies in the American Journal of Clinical Nutrition found that the countries with the highest intake of dairy products also had the highest rates of fracture from osteoporosis. There are plenty of excellent nondairy sources of calcium on this list; fill your plate with a wide range of sources for the best bone benefit.