WEST LAFAYETTE, Ind.—According to new research from Purdue University, overweight and moderately obese postmenopausal women who consume high-protein diets rich in meat and poultry to shed pounds may be at risk for developing low bone mineral density faster than women who eat normal protein diets without any meat.
The study, published online in the Journal of Gerontology: Medical Sciences, analyzed data from two controlled diet studies on postmenopausal women aged 43 to 80. The first study reduced 28 women's individual daily diets by 750 calories to achieve a 1.5-pound weight loss each week for 12 weeks. Fifteen participants ate meat-free diets with protein from vegetarian, dairy and egg sources, comprising 18 percent of each woman's energy intake. The amount of protein was comparable to the recommended dietary allowance of 0.36 grams of protein per pound of body weight per day. Diets for the other 13 women were composed of 30 percent of energy from protein with 40 percent of the protein from lean pork and 60 percent of the protein from vegetarian, dairy and egg sources. On average, the women each lost about 19 pounds; however, those who ate the higher-protein, meat-containing diet lost bone mineral density.
In the second study, 43 postmenopausal women each ate a 1,250-calorie diet for nine weeks. All consumed the same 1,000-calorie vegetarian diet; however, 15 received 250 calories from chicken breast meat, 14 received 250 calories from beef tenderloin, and 14 received 250 calories from shortbread cookies and sugar-coated chocolates. Eleven women acted as the control group. All women who ate the energy-reduced diets successfully lost weight; however, the groups that consumed the higher-protein meat-containing diets also lost bone mineral density compared to the control group.
"We know that when overweight, postmenopausal women reduce their energy intake to successfully lose weight, they can lose less lean body mass when they consume higher amounts of protein and include lean meats, such as pork loins, ham, beef and chicken, in their diet," said Wayne W. Campbell, professor of foods and nutrition. "However, we also found that these older women lost bone mineral density faster than women who consumed normal protein diets that did not contain any meats. This finding is of concern for this age group that is susceptible to osteoporosis."
