Calcium supplements have been in the news a lot this week, with revelations just yesterday that the nutrient is more effective when combined with phosphorous contrasting with news a day earlier that calcium supplements can help combat colon cancer.
Today, the news is good, and comes from a new study by Tufts University researchers. They claim that elderly Americans who are on high protein diets and have adequate calcium intake can reverse bone loss usually associated with high protein diets. The study was 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 adults who ate a diet high in protein as well as the supplements 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," said Bess Dawson-Hughes, lead author of the study.
The recommended daily allowance (RDA) for calcium in the US is 1,200 milligrams, equivalent to one calcium supplement (500 mg), one cup of fat-free milk, one 8-oz. serving of yoghurt, and a 1-oz. slice of cheese, the researchers said.
The average protein intake by the volunteers in the study was 79 grams per day, 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, the researchers said.
The type of protein consumed - plant or animal - did not make a difference in the effect on bone mass density, the study showed. Instead, it was the amount of protein in the diet which was significant.
The Tufts researchers said that protein might help calcium absorption when there is sufficient calcium in the diet through food and/or supplementation. Earlier results were contradictory. For example, 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," said 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."