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Some studies indicate that high levels of protein consumption (but within a normal range for a standard North American diet) correlate with increased excretion of calcium. One suggestion is that this may lead to greater risk for osteoporosis (lose of calcium from the bone). Three studies are cited below: American Journal of Clinical Nutrition 59: 1356-1361, 1994. Thomas Remer & Friedrich Manz. Estimation of the renal net acid excretion by adults consuming diets containing variable amounts of protein. Three men and three women participated in this study. For purposes of this page, I am only describing some of the work. Three levels of protein intake were compared: Low protein had 49 grams of protein/day; Medium was 95 grams; High was 120 grams. Calcium excretion was approximately twice as much in the medium as compared to the low; and 2.25 times as much in the high as in the low. One problem with this work is that the diets differed in other than just protein content. Journal of Nutrition 111: 545-552, 1981. Michael B Zemel, Sally A Schuette, Maren Hegsted, & Hellen M Linkswiler. Role of the sulfur-containing amino acids in protein-induced hypercalciuria in men. For purposes of this page, this paper is significant because it confirmed a correlation between protein consumption and calcium excretion in urine. Eight men participated: They compared the same men consuming 50 g versus 150 g of protein. At the higher protein consumption, excretion of calcium was double that at the lower protein consumption. This paper, the diets were as identical as could be managed. To generate the difference in protein level, a high protein containing bread and a lower-protein containing bread were eaten. Obviously that meant some adjustments to carbohydrates and fat consumption, but it didn't mean that different foods were eaten. Journal of Nutrition 100: 1425-1430, 1970. Nancy E Johnson, Emerita N Alcantara & Hellen Linkswiler. Effect of level of protein intake on urinary and fecal calcium and calcium retention of young adult males. In this study, 3 male college students were fed a high protein containing diet for 45 days and then switched to a low protein containing diet; 3 other males were first given the diet low in protein then switched to the diet high in protein. Every subject showed increased calcium excretion in urine when on the high protein diet. In the discussion the authors suggest, and cite others that have also suggested, that a longterm effect of a high protein diet may be to increase one's risk of osteoporosis (loss of calcium from bones). The quantity of protein is within what might be considered normal for a North American: the high protein diet contained 141 g of protein; the low protein contained 48 g of protein. In this study other changes in the diet were minimized, yet calories consumed the same. |
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The University of Arizona Last update Apr 10, 1999 schmidtz@u.arizona.edu willott@u.arizona.edu "http://research.biology.arizona.edu/mosquito/willott/323/project/eating/ptnca.html" All contents copyright © 1998. All rights reserved. |