Calcium Interplay Important to Bone Health
By Rosalie Marion
April 24, 2002
Its no secret that the incidence
of bone fractures increases among the elderly. Adding to that concern, some
scientists theorize that high-protein diets may leach calcium from bone, itself
leading to bone loss. Now scientists funded by the
Agricultural Research Service have
released a three-year study suggesting that bone mineral density (BMD) may
actually benefit from high-protein diets--with one caveat. The high-protein
diet must also meet the recommended dietary allowance of calcium and vitamin D.
The researchers heading the study are with the
Calcium and Bone
Metabolism Laboratory at the Jean
Mayer USDA Human Nutrition Research Center on Aging at Tufts University in
The studys design, which looked at 342 men and women older than 65,
included prescreening the amount of calcium each consumed. Only those who did
not normally consume high amounts of calcium were chosen. In addition, the
study included only participants whose baseline BMD measurements proved average
for those over 65.
The researchers supplemented half the participants with 500 milligrams (mg)
of calcium and 700 International Units of vitamin D daily. The other half were
given placebos. Halfway through the study, dietary intakes of protein, calcium,
vitamin D and other nutrients were assessed using a self-administered, but
staff-monitored, food-frequency questionnaire. The results showed the mean
protein intake for all participants was 79 grams per day. For the calcium- and
vitamin D-supplemented group, the mean daily calcium intake was 1,346 mg per
day. For the placebo group, calcium intake was just 871 mg per day--well below
the recommended 1,200 mgs daily for those over 50.
The participants were tested every six months--six times total--for BMD. The
study, published in Aprils "American
Journal of Clinical Nutrition," showed that a high-protein diet had
favorable effects on bone density in the calcium-supplemented group, but not in
the unsupplemented group. This suggests that the calcium worked synergistically
with the protein to mitigate bone loss. The researchers agree the report proves
more research is needed in this area.
ARS is the U.S. Department of
Agricultures chief scientific research agency.