High Protein Diet May Benefit Bone Health in Elderly
BOSTON--A high protein diet may be beneficial to bone health in the elderly, but only in the presence of adequate calcium and vitamin D intakes, according to researchers from the Human Nutrition Research Center on Aging at Tufts University (www.hnrc.tufts.edu). Researchers, led by Bess Dawson-Hughes, M.D., senior scientist and chief, conducted a secondary analysis of their previous calcium/vitamin D intervention study to determine whether protein consumption affected bone health in the elderly.
The study authors originally compared the effects of calcium and vitamin D supplementation vs. placebo on bone mineral density in 342 healthy elderly men and women (age 65 and older). The secondary analysis, which will be published in the April issue of the American Journal of Clinical Nutrition (www.ajcn.org), determined that protein intake also affects bone health, but only in the presence of adequate calcium and vitamin D. "We found that protein has a favorable effect on changes in bone density if you have an adequate calcium and vitamin D intake," Dawson-Hughes said. "But, it has a neutral effect if you have an inadequate calcium and vitamin D intake. So, in the placebo group, more and more protein wasn't helpful."
This finding could explain the mixed study results on protein and bone density, according to Dawson-Hughes. "The literature is very mixed," she said. "Some studies show protein is harmful to bone, others show that it is not. ... [Our results] may help to explain the variety of findings out there--it depends on how much calcium and vitamin D the groups consume whether you'd see a positive effect."
Study participants either consumed a 500 mg/d supplement of calcium and approximately 700 mg/d of dietary calcium, as well as approximately 200 IU/d of vitamin D, or placebo for three years. Calcium intakes were below the recommended daily allowance (RDA), although they were higher than the majority of people in this age group, according to Dawson-Hughes. However, protein intakes were generally above the RDA. While the RDA for protein is between 40 g/d and 60 g/d, study participants averaged 79 g/d, with those in the highest third of protein intake averaging 96 g/d.
"The average intake of the lowest third of the [participants] was higher, in fact, than the RDA for protein," Dawson-Hughes said. "So, we're not talking about taking really malnourished people and bringing them up to the RDA, which is an interesting perspective. It raises the possibility that the elderly might benefit from more than the current RDA [of protein]. But that's something that's going to take a lot more work."