Protein intake: effects on bone mineral density and the rate of
bone loss in elderly women.
Rapuri PB, Gallagher JC, Haynatzka V.
Bone Metabolism Unit, Creighton University, School of Medicine, Omaha, NE 68131,
USA. thiyyari@creighton.edu
BACKGROUND: The role of dietary protein in bone metabolism is controversial.
OBJECTIVE: We investigated the associations of dietary protein intake with
baseline bone mineral density (BMD) and the rate of bone loss over 3 y in
postmenopausal elderly women. DESIGN: Women aged 65-77 y (n = 489) were enrolled
in an osteoporosis intervention trial. We studied the associations of protein
intake as a percentage of energy with baseline BMD and the rate of bone loss in
96 women in the placebo group (n = 96). We also examined the effect of the
interaction of dietary calcium intake with protein intake on BMD. RESULTS: In
the cross-sectional study, a higher intake of protein was associated with higher
BMD. BMD was significantly higher (P < 0.05) in the spine (7%), midradius (6%),
and total body (5%) in subjects in the highest quartile of protein intake than
in those in the lower 2 quartiles. This positive association was seen in women
with calcium intakes > 408 mg/d. There was no significant effect of protein
intake on hip BMD. In the longitudinal study of the placebo group, there was no
association between protein intake and the rate of bone loss. CONCLUSIONS: The
highest quartile of protein intake (: 72 g/d) was associated with higher BMD in
elderly women at baseline only when the calcium intake exceeded 408 mg/d. In the
longitudinal study, no association was seen between protein intake and the rate
of bone loss, perhaps because the sample size was too small or the follow-up
period of 3 y was not long enough to detect changes.
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