Date:   5/22/2009 2:51:20 AM ( 16 y ago)
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URL:   https://www.curezone.org/forums/fm.asp?i=1423910

http://www.ajcn.org/cgi/reprint/68/1/3.pdf


Does calcium interfere with iron absorption?

"Several animal studies have clearly shown that calcium interferes with dietary iron absorption and that addition of calcium to the diet may even induce iron deficiency (1, 2). Epidemiologic data also suggest that calcium interferes with iron absorption. In an extensive study in France (n = 1108), serum ferritin and hemoglobin concentrations were negatively and significantly correlated with the intake of calcium (3). Similar findings were made in a study on French students (n = 476) (4). In a longitudinal study in adolescent girls, high intake of calcium was associated
with a lower serum ferritin concentration (5). However,
inconsistent and conflicting results have been reported even when the methods and experimental design seem to be adequate. Moreover, the same research group has sometimes reported conflicting results. For example, one group found an inhibition of iron absorption by calcium in 2 studies (6, 7) but no effect in another (8). Similarily, we reported divergent results in 2 studies (2, 9). In this issue of The American Journal of Clinical Nutrition (10), 2 studies are presented on the effect of calcium on iron absorption with contradictory results. The question arises: Are there some special problems or pitfalls in studies on the interaction of calcium with iron absorption?"


http://findarticles.com/p/articles/mi_m0887/is_n3_v10/ai_10600750/


Calcium and iron absorption: two reports

"When taken without food, calcium carbonate did not inhibit the absorption of ferrois sulphate; however, at relatively high doses (600 mg), both calcium citrate and calcium phosphate significantly reduced iron absorption, by 49% and 62%, respectively. When taken with food, all three calcium supplements inhibited the absorption of the iron supplement, by 40-57%. They also inhibited the absorption of nonheme food iron. The degree of inhibition varied with the composition of the test meal.

These findings suggest that individuals who need both calcium and iron supplements should choose calcium carbonate and take it between meals. If taken with meals, "calcium supplements used regularly may make it more difficult to meet daily iron requirements." James D Cook, Sandra A Dassenko, and Paul Whittaker, Calcium Supplementation: Effect on Iron Absorption, American J Clinical Nutrition 53(1):106-111 (Jan 1991)"

"The same problem can occur when calcium from foods is consumed with an iron source. Researchers from the University of Goteborg, Sweden, evaluated the effects of various sources of dietary calcium on iron absorption in normal adult volunteers using a double-radiosotope technique. The researchers initially planned to use wheat rolls as the iron-containing test meal, and to add calcium to the four before baking. However, it was found that the addition of calcium reduced phytate degradation during fermentation and baking, thus interferring indirectly with iron absorption.

To avoid this problem, a second set of experiments was conducted in which calcium was added to rolls after baking. It was found that calcium accded in this way had a direct dose-related inhibiting effect on iron absorption, reducing it by 50-60% at calcium doses of 300-600 mg. When 165 mg calcium was given as milk, cheese, or calcium chloride, iron absorption was again reduced by 50-60%. Absorption of heme iron from a hamburger meal was also reduced by 165 mg calcium."


http://www.ncbi.nlm.nih.gov/pubmed/1600930


Calcium and iron absorption: mechanism of action and nutritional importance.

"We investigated the inhibitory effect of calcium on iron absorption in 57 human subjects. Three studies suggested that the effect is not located in the gastrointestinal tract. The presence of phytate in a meal and formation of calcium-iron-phytate complexes is not a prerequisite for the inhibition. The relative increase in iron absorption by ascorbic acid was the same in meals with and without calcium, suggesting that calcium did not influence the balance between enhancing and inhibiting ligands in the gastrointestinal lumen. No inhibiting effect on iron absorption was seen when adding 3 mg calcium to 0.01 mg iron (molar ratio Ca/Fe = 420). Previous studies showing a marked inhibition by calcium had a lower molar ratio, but greater amounts of calcium were given. This suggests that a minimal concentration of calcium is needed to achieve an effect. The present results indirectly support our original hypothesis that the inhibitory effect of calcium on iron absorption is situated within the intestinal mucosal cells. The practical nutritional implications of the inhibitory effect of calcium are considerable since addition of milk, milkshake or cheese to common meals such as pizza or hamburger meals reduced iron absorption by 50-60%. It is recommended to reduce the intake of dairy products with the main meals providing most of the dietary iron, especially for those having the highest iron requirements i.e. children, teenagers and women at childbearing age."


http://www.ncbi.nlm.nih.gov/pubmed/1984335?ordinalpos=1&itool=EntrezSystem2.P...


Calcium: effect of different amounts on nonheme- and heme-iron absorption in humans.

"We investigated the effect of calcium on iron absorption in 126 human subjects. Addition of calcium chloride to wheat rolls significantly reduced iron absorption. Doses between 40 and 600 mg Ca were studied. The inhibition was clearly dose related up to 300 mg Ca. Calcium added to the dough when making the rolls reduced phytate degradation during fermentation and baking. As little as 40 mg Ca added to 80 g flour reduced phytate degradation by 50%, thus increasing the phytate content of the rolls to levels interfering with iron absorption. Calcium also had a direct dose-related inhibiting effect on iron absorption, noted by adding calcium to the rolls after they had been baked instead of to the dough. Iron absorption was reduced by 50-60% at doses of 300-600 mg Ca. Giving 165 mg Ca as milk, cheese, or calcium chloride reduced absorption by 50-60%. The same amount of calcium also significantly reduced heme-iron absorption, suggesting that the effect of calcium is related to the mucosal transfer of iron. The observed marked inhibitory effect on iron absorption of calcium in amounts frequently encountered in normal meals has important nutritional implications."
 

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