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Am J Clin Nutr. 2002 Dec;76(6):1345-50.

Relative bioavailability of calcium-rich dietary sources in the elderly.

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Mineral Bioavailability Laboratory, Jean Mayer US Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston.



The recent increase in the dietary calcium recommendation from 800 to 1200 mg/d for persons aged > 51 y has made it important to identify alternative high-calcium dietary sources that the elderly can use in meeting their calcium requirement.


We determined the bioavailability of calcium from 3 different sources: orange juice fortified with calcium-citrate malate, skim milk, and a calcium carbonate supplement.


Twelve subjects [9 women and 3 men with a mean (+/- SEM) age of 70 +/- 3 and 76 +/- 6 y, respectively] consumed low-calcium (300 mg/d) and high-calcium (1300 mg/d) diets for three 1-wk periods each during a 6-wk crossover study. The acute biochemical response to calcium from each of the 3 sources was assessed during a 4-h period after the initial breakfast meal of the high-calcium diet.


Postprandial suppression of serum parathyroid hormone did not differ significantly between the test meals containing calcium-fortified orange juice, the calcium carbonate supplement, and milk. This finding suggests that the calcium bioavailability from the 3 sources was equivalent. During the 1-wk high-calcium diet periods, fasting serum calcium increased by 3% (P < 0.0001), serum 1,25-dihydroxyvitamin D decreased by 20% (P < 0.0001), and a biomarker of bone resorption (serum N-telopeptide collagen cross-links) decreased by 14% (P < 0.02) compared with the low-calcium diet period. However, no differences among the supplemental calcium sources were found in these calcium-responsive measures or fasting serum parathyroid hormone concentration.


In elderly subjects, the calcium bioavailability of the 3 high-calcium dietary sources tested was equivalent, during both the acute postprandial and longer-term periods.

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