An Overview of current information on bioavailability of dietary iron to humans
1983
Morris, Eugene R.
Extract: Bioavailability factors can greatly modify the absorption of dietary iron consumed in different meals by an individual. A greater percentage of heme iron is generally absorbed from animal tissues than of nonheme iron of either animal or plant food. The amount of meat in a meal is the only bioavailability factor known to influence absorption of heme iron. Absorption of iron from the exchangeable nonheme iron pool of a meal is influenced by both enhancing and inhibiting substances or factors. Ascorbic acid, meat, fish, and poultry enhance absorption of nonheme iron; hence, meals may be classified according to relative bioavailability depending on their content of meat, fish, poultry and/or ascorbic acid. Some low-molecular-weight organic acids also may increase the bioavailability of nonheme iron. Synthetic and metal-chalating agents added to foods, tea, and coffee, will inhibit absorption of nonheme iron in a concentration-dependent manner. Wheat bran, soy products, cow's milk, and egg tend to decrease bioavailability of nonheme iron when included in a meal; however, the effect of compounds thought to be responsible for this (phytate, fiber, phosphoproteins) is dependent on chemical form and concentration. In some foods there may be unidentified inhibitors, or interaction between compounds, to inhibit absorption of nonheme iron. Current information permits estimation of relative bioavailable iron in a meal. (author/wz)
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