Inhibitory effects of dietary calcium on the initial uptake and subsequent retention of heme and nonheme iron in humans: comparisons using an intestinal lavage method.

Background: Calcium is the only reported dietary inhibitor of both heme- and nonheme-iron absorption. It has been proposed that the 2 forms of iron enter a common pool in the enterocyte and that calcium inhibits the serosal transfer of iron into blood.

Objectives: We aimed to ascertain whether the inhibitory effect of calcium occurs during initial mucosal uptake or during serosal transfer and to compare the serosal transfer of heme and nonheme iron, which should not differ if the 2 forms have entered a common mucosal iron pool.

Increased contractility of cardiomyocytes from copper-deficient rats is associated with upregulation of cardiac IGF-I receptor.

Hearts from severely Cu-deficient rats show a variety of pathological defects, including hypertrophy and, in intact hearts, depression of contractile function. Paradoxically, isolated cardiomyocytes from these rats exhibit enhanced contractile properties. Because hypertrophy and enhanced contractility observed with other pathologies are associated with elevation of insulin-like growth factor-I (IGF)-I, this mechanism was examined for the case of dietary Cu deficiency.

Controlled substitution of soy protein for meat protein: effects on calcium retention, bone, and cardiovascular health indices in postmenopausal women.

In a controlled feeding study, the effects of substituting 25 g soy protein for meat on calcium retention and bone biomarkers were determined. Postmenopausal women (n = 13) ate two diets that were similar, except that, in one diet, 25 g high-isoflavone soy protein (SOY) was substituted for an equivalent amount of meat protein (control diet), for 7 wk each in a randomized crossover design. After 3 wk of equilibration, calcium retention was measured by labeling the 2-d menu with (47)Ca, followed by whole-body counting for 28 d.

Controlled high meat diets do not affect calcium retention or indices of bone status in healthy postmenopausal women.

Calcium balance is decreased by an increased intake of purified proteins, although the effects of common dietary sources of protein (like meat) on calcium economy remain controversial. We compared the effects of several weeks of controlled high and low meat diets on body calcium retention, using sensitive radiotracer and whole body scintillation counting methodology. Healthy postmenopausal women (n = 15) consumed diets with similar calcium content (approximately 600 mg), but either low or high in meat (12 vs.

Initial uptake and absorption of nonheme iron and absorption of heme iron in humans are unaffected by the addition of calcium as cheese to a meal with high iron bioavailability.

Background: Quantitative data on the mucosal uptake and serosal transfer of nonheme-iron absorption in humans and the effects of calcium on these components are limited.

Objective: Our objective was to measure the initial mucosal uptake and the subsequent serosal transfer of nonheme iron and to determine the effects of adding calcium to a meal on both heme- and nonheme-iron retention.

Design: Whole-gut lavage and whole-body scintillation counting methods were applied to determine the 8-h uptake of nonheme iron and the 2-wk retention (absorption) of heme and nonheme iron in healthy adults (n = 17) after the consumption of meals of radiolabeled food.