Health risks of high protein diets.

Health risks of high protein diets. Watch More Healthy Vegetarian Ideas

Your high-protein diet may help you lose weight, but it could also increase your risk of osteoporosis. Recent research in the Journal of Gerontology found that overweight postmenopausal women on a weight-loss diet who ate meaty, protein-rich diets lost bone density faster than those who consumed moderate-protein vegetarian diets.

In the study, one group of women ate a meat-free diet made up of 18 percent protein; another group followed a diet of 30 percent protein (from pork, dairy, egg and vegetarian sources). Both groups lost an average of 19 pounds over 12 weeks, but the meat-eaters lost bone density too. (The researchers examined the effects of protein from chicken and beef and found similar results.)

"Meat contains high levels of sulfur-containing amino acids that promote acid production, and that acid load may promote bone breakdown," says Wayne W. Campbell, Ph.D., professor of foods and nutrition at Purdue. Postmenopausal women's bone health is already compromised by a natural decrease in bone-protecting estrogen.

Campbell recommends that, for bone health, postmenopausal women get adequate, not excessive, protein-between 16 and 18 percent of calories (that's 50 to 56 grams in a 1,250-calorie diet, which is about what the women in the studies ate), with an emphasis on plant-based sources. Top sources of plant-based proteins include beans, lentils, whole grains and nuts.

November/December 2010