In a study in the April 2002 American Journal of Clinical Nutrition, researchers at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University demonstrated that adequate calcium and vitamin D can reverse bone loss that can occur with high protein diets.
Three hundred forty-two healthy men and women over the age of sixty-five were randomized to receive 500 milligrams calcium per day along with vitamin D or a placebo for a period of three years, and diets and bone mass density were assessed. Protein intake for the participants ranged from 79 to 96 grams per day, well above the recommended protein intake for healthy people of 40 to 60 grams per day. A high protein diet is common for people following the Atkins plan or the South Beach Diet and may benefit older individuals in preventing muscle wasting and promoting wound healing.
The group receiving calcium experienced an increase in bone mass density, whereas the placebo group experienced a reduction in calcium levels with rising protein intake. Protein source did not effect bone density. The researchers explained that sufficient calcium intake may be conducive to protein aiding calcium absorption.
Lead author, Senior Scientist and Chief of the Calcium and Bone Metabolism Laboratory at the Human Nutrition Research Center on Aging, Bess Dawson-Hughes, MD summarized, "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. These results help us to better understand the mechanics behind calcium and vitamin D supplementation and their effect on bone mass density. 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."
Dawson-Hughes B, Harris SS. Calcium intake influences the association of protein intake with rates of bone loss in elderly men and women. Am J Clin Nutr. 2002 Apr;75(4):773-9.