Time course of calcium absorption in humans: Evidence for a colonic component
- 79 Downloads
We examined the time course of calcium absorption (CaAbs) in 155 studies, using a double isotope technique. The subjects were 118 healthy peri-menopausal women (mean age 53.3 years), studied as impatients under metabolic balance conditions. We measured the ratio of radiolabeled calcium (oral:IV) in serum and urine for 144 hours after the oral dose, and generated a composite CaAbs curve for all 155 studies using normalized data. Although CaAbs was 80.9% complete at 3 hours, it was still only 95.8% complete at 7 hours; the remaining 4.2% was absorbed in a slower late component, and did not reach completion until about 26 hours. The rapid initial component probably represents mainly small intestinal absorption and the late component, colonic. At the dietary intakes of our subjects, we estimate the size of the late component at about 6.8 mg/day. For fully accurate measurements of CaAbs, it is necessary to allow for this small late component.
Key wordsCalcium absorption Calcium nutrition Colonic absorption
Unable to display preview. Download preview PDF.
- 2.Favus MJ (1965) Factors that influence absorption and secretion of calcium in the small intestine and colon. Am J Physiol 248:G147–157Google Scholar
- 3.Ammann P, Rizzoli R, Fleisch H (1986) Calcium absorption in rat large intestine in vivo: availability of dietary calcium. Am J Physiol 251:G14–18Google Scholar
- 4.Grinstead WC, Pak CYC, Krejs CJ (1984) Effect of 1,25-dihydroxyvitamin D3 on calcium absorption in the colon of healthy humans. Am J Physiol 247:G189–192Google Scholar
- 7.Bronner F (1962) Experimental studies of calcium absorption in man. Bibl Nutr Dieta 3:22–31Google Scholar
- 9.Magee DF, Dalley AF (1986) Digestion and the structure and function of the gut. Karger, Basel (Switzerland), p 183Google Scholar
- 12.James WPT, Branch WJ, Southgate DAT (1978) Calcium binding by dietary fibre. Lancet 639Google Scholar