Harvard Women's Health Watch

In Brief: Dietary calcium may be better for bones than calcium pills

In Brief

Dietary calcium may be better for bones than calcium pills

Most of us know that getting enough calcium is important to bone health, but a study suggests that the source of calcium may be at least as important as the amount. In the May 2007 issue of the American Journal of Clinical Nutrition, researchers at Washington University in St. Louis reported that women who get their calcium mostly from food have higher bone mineral densities (BMDs) than those who get their calcium mostly from supplements. The study involved 183 healthy postmenopausal women who did not smoke or take medications that could affect estrogen levels (estrogen helps boost BMD) and who did not have medical conditions that would interfere with bone metabolism.

For seven days, subjects recorded their daily intake of foods containing calcium and calcium from supplements. The researchers reviewed the data and divided the women into three groups: those getting at least 70% of their calcium from food, those getting at least 70% of their calcium from supplements, and those whose calcium intake was more evenly distributed between supplemental and dietary sources. Although the women getting most of their calcium from food consumed an average of only 830 milligrams (mg) per day, they had much higher BMDs than the women getting most of their calcium from supplements, who got 1,033 mg per day. Women who balanced their intake between diet and supplements had the highest BMDs — and also, at 1,620 mg per day, the highest calcium consumption.

Selected calcium-rich foods

Food

Calcium (mg)

Yogurt, plain, low-fat, 8 oz.

415

Yogurt, fruit, low-fat, 8 oz.

345

Milk, skim or fat-free, 1 cup

306

Milk, 1% milkfat, 1 cup

290

Cheese, mozzarella, 1 oz.

207

Cheese, cheddar, 1 oz.

204

Sardines, canned, w/bones, 3 oz.

325

Salmon, canned, w/bones, 3 oz.

181

Tofu,* firm, 4 oz.

163

Rhubarb, frozen, cooked, 1 cup

348

Collards, frozen, cooked, 1 cup

357

Spinach,** frozen, cooked, 1 cup

291

Kale, frozen, cooked, 1 cup

179

Bok choy, fresh, cooked, 1 cup

158

*Tofu made with calcium sulfate.

**Spinach contains oxalic acid, which interferes with calcium absorption.

Source: www.nal.usda.gov/fnic/foodcomp/Data/SR17/wtrank/sr17a301.pdf.

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