A new study by Tufts University researchers reports elderly Americans who are on high protein diets and have adequate calcium intake can reverse bone loss usually associated with high protein diets.
In a randomized, placebo-controlled study, published in the April issue of The American Journal of Clinical Nutrition, researchers from the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University (HNRCA) gave 342 healthy men and women over age 65 either daily calcium (500 milligrams) and vitamin D supplements, or a dummy pill for three years. During the study, the researchers reviewed the volunteers’ diets (specifically their calcium and protein intake) and bone mass density.
The results show that the supplemented adults who ate a diet high in protein displayed significant positive effects on their bone mass density. On the other hand, for the volunteers who took the placebo, calcium levels absorbed into their bloodstream were reduced as they consumed more protein.
“Our results suggest that a higher calcium intake is going to be protective against any adverse effects of protein on bone, and may allow protein to have a positive effect,” says Bess Dawson-Hughes, M.D., lead author of the study, and senior scientist and chief, Calcium and Bone Metabolism Laboratory, Jean Mayer USDA HNRCA at Tufts University.
The recommended daily allowance (RDA) for calcium is 1200 milligrams, which can easily be achieved by consuming one calcium supplement (500 mg), one cup of fat-free milk, one 8-oz. serving of yogurt, and a 1-oz. slice of cheese.
The average protein intake by the volunteers in the study was 79 grams per day (g/d), and the adults who ate the most protein averaged 96 g/d. The recommended protein intake for a healthy person is between 40-60g/d. Elderly people may be on a high protein diet to increase their caloric intake, help wound healing and maintain muscle mass. Additionally, like millions of Americans, they may desire to lose weight using a high protein, low carbohydrate plan. The type of protein consumed — plant or animal — did not make a difference in the effect on bone mass density, rather it was the amount of protein in the diet.
Tufts researchers note that when there is sufficient calcium in the diet (through food and/or supplement), protein may aid in calcium absorption, as reported here. Previous studies of this kind have reported contradictory results. One study showed a low-protein diet was associated with a greater rate of bone loss, whereas another study associated a high-protein diet with a greater rate of bone loss. Scientists are not yet able to agree on the effect of protein in the diet on bone, but they have concurred on the negative impact of low-calcium diets on bone density.
“These results help us to better understand the mechanics behind calcium and vitamin D supplementation and their effect on bone mass density,” explains Dawson-Hughes. “This study is a significant confirmation that adequate calcium in the diet is crucial. This report, however, also shows that there is much more research needed in this area.”