Calcium is Not All You Need for Strong Bones

Source: Tufts University
May 16, 2002 (Reviewed: April 19, 2004)

When you think of keeping your bones strong, you probably think first of calcium. But according to recent research, you may also need adequate protein and vitamin D, in addition to calcium. Tufts University researchers recently examined the relationship between these nutrients and their effect on bone health. The results are published in the American Journal of Clinical Nutrition.

An appraisal of diet and bone health

The participants were 342 healthy men and women aged 65 and older. At the beginning of a 3-year period, their bone density, an indicator of bone health, was measured in the hip, spine, and the entire body using an x-ray device. The volunteers were then randomly assigned to receive either daily supplements of calcium (500 mg) and vitamin D (700 IU), or sugar pills (placebos). They also filled out detailed dietary questionnaires so that the researchers could assess their intakes of protein, calcium, vitamin D, total calories, and other nutrients. Investigators also measured the absorption rate of calcium in each volunteer, using a blood test.

Protein and supplements affect bone mass

After three years, the researchers tested the volunteers' bone density again. They found significantly less bone loss in the volunteers who took the supplements and who had higher protein intakes (18-30% of their total calories from protein), compared with those who took the supplements but who had lower protein intakes (10-15% of total calories from protein). Protein intake did not have any effect - negative or positive - on bone mass in the volunteers who took a placebo instead of supplements.

Protein also seemed to influence how well the body absorbed calcium, but only in people who didn't get enough calcium. The volunteers taking the placebo, on average, consumed less calcium. They also absorbed proportionally less calcium as the amount of protein they consumed increased. On the other hand, those taking the supplements not only had higher calcium intakes, but they also had a higher absorption rate.

What it all means

Getting adequate protein, calcium, and vitamin D is essential for strong bones. When protein intake is low, bone health may take a backseat to the body's other uses for protein. But this isn't a recommendation for an excessively high-protein diet, like those made popular by many recent diet books. The recommended amount of protein for healthy adults is 0.8 grams per kilogram of body weight per day. People who eat a balanced diet that includes food from all food groups can easily achieve this.

On the other hand, many people don't seem to get enough calcium and vitamin D. To make sure you do, keep these points in mind:

• People over 65 need 1,200 mg calcium and 400 IU vitamin D (this goes up to 600 IU for people over 70).
• Some of the best dietary sources of calcium are low-fat milk, calcium-fortified orange juice, hard cheese, and yogurt.
• The best dietary sources of vitamin D are low-fat milk and fortified cereals.
• You may also wish to talk to your doctor about taking supplements of calcium and vitamin D.

Source

• Calcium intake influences the association of protein intake with rates of bone loss in elderly men and women. B. Dawson-Hughes, S. Harris, Am J Clin Nutr, 2002, vol. 75, pp. 773--779

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