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Aging Bone Mineral Density Better With High Protein Diet Plus Extra Calcium, Vitamin D

Consuming a high protein diet and taking calcium and vitamin D supplements could help healthy older men and women increase total body bone mineral density (BMD).

Researchers from Tufts University in Boston, Massachusetts, United States, say they found no evidence that the type of protein -- animal or plant -- mattered: "BMD may be improved by increasing protein intake in many older men and women, as long as they meet the currently recommended intakes of calcium and vitamin D.

They add, "Further research is needed to determine whether a similar association would be observed in older adults consuming these nutrients from other sources."

A 20 percent higher protein intake in older adults supplemented with calcium and vitamin D is associated with favourable changes in total body BMD.

The researchers examined the associations between protein intake and change in BMD in 342 healthy men and women aged 65 years and older, randomised in a three-year, placebo-controlled trial of calcium and vitamin D supplementation. Supplements included 500 milligrams of calcium as calcium citrate malate and 17.5 µg (700 IU) vitamin D daily.

Participants were almost equally divided between men and women: 161 men and 181 women.

The investigators assessed protein intake at 18 months using a food-frequency questionnaire. They used dual-energy X-ray absorptiometry to assess BMD in participants every six months.

Participants in the supplemented group took in a mean of 1,346 mg of total calcium per day. Those in the non-supplemented group took in 871 mg/d. Mean protein intake for members of both groups reached 79.1 grams per day.

Higher protein intake was significantly associated with a favourable three-year change in total body BMD in the supplemented participants. Placebo participants did not have this change.

Pattern of change in femoral neck BMD with increasing protein intake was similar to that for total body BMD in supplemented participants, they note: "Calcium intake also appeared to influence the association of protein intake with absorbed calcium."

At the lower mean calcium intake of 800 mg/d, a 20 percent higher protein intake was associated with a 23 percent lower absorbed amount of calcium. At the higher calcium intake, absorbed calcium was greater overall. It did not change significantly with increasing protein intake.
American Journal of Clinical Nutrition, 2002; 75: 773-779.

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