Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/21/2002
Publication Date: 5/1/2003
Citation: Roughead, Z.K., Johnson, L.K., Lykken, G.I., Hunt, J.R. 2003. Controlled high meat diets do not affect calcium retention or indices of bone status in healthy postmenopausal women. Journal of Nutrition. 133:1020-26.
Interpretive Summary: A high meat intake has been cited as a risk factor for the development of osteoporosis. This is based on earlier studies which have reported that when the intake of purified proteins is increased, less calcium is retained in the body. However, the effects of consuming common sources of protein (like meat) on calcium retention are controversial. One of the sources for the controversy is that methods used previously to measure calcium retention have been insensitive. Also, the duration of most studies has been only a few days which does not allow for adaptation to the test diets. In this study, we used a sensitive method which monitors the retention of a calcium tracer in the body with a whole body scintillation counter. We also used two carefully planned diets for a longer duration of several weeks. Fifteen healthy postmenopausal women ate these diets which had similar calcium content (~ 600 mg), but were either low (~1.6 oz/day) or high (10.5 oz/day) in meat for 8 weeks each, in random order. After 4 weeks of equilibration on each diet, we monitored the retention of the calcium tracer for 28 days. We also measured indicators of bone metabolism in urine and blood samples. We found that the amount of calcium retained in the body was the same (16% on the low and 17% on the high meat diet). The urinary acidity, which was initially higher on the high meat diet, decreased with time. Also, these diets did not affect the amount of calcium lost in the urine or any of the indicators of bone metabolism. We have concluded that consuming a high meat diet does not adversely affect calcium retention or bone health in postmenopausal women.
Technical Abstract: Calcium balance is impaired by an increased intake of purified proteins, but the effects of common dietary sources of protein (like meat) on the calcium economy remain controversial. Sensitive radiotracer and whole body scintillation counting methodology were used to compare the effects of several weeks of controlled high and low meat diets on body calcium retention. Healthy postmenopausal women ate diets with similar calcium content (~ 600 mg), but either low or high in meat (12% vs. 20% of energy as protein) for 8 wk each, in a randomized crossover design. After 4 wk of equilibration on each diet, calcium retention was measured by extrinsically labeling the 2-d menu with 47Ca, followed by whole body scintillation counting for 28 days. Urinary and blood indicators of bone metabolism were also determined on each diet. Calcium was similarly retained during the high and low meat dietary periods (day 28, mean ± pooled SD: 17.1 vs.15.6%, ± 0.6%, respectively; P=0.09). An initially higher renal acid excretion on the high meat, versus the low meat diet, decreased significantly with time. The diets did not affect urinary calcium loss or indicators of bone metabolism. Under controlled conditions, a high- compared with a low-meat diet for 8 wk did not affect calcium retention or biomarkers of bone metabolism in healthy postmenopausal women. Calcium retention is not impaired by consuming protein from common dietary sources such as meat.