Submitted to: Food and Nutrition Bulletin
Publication Type: Review Article
Publication Acceptance Date: 12/2/2000
Publication Date: N/A
Citation: Interpretive Summary: Iron and zinc deficiencies are common world-wide among populations subsisting on diets composed of cereals. The cereal compound, phytate, readily binds iron and zinc in an insoluble form so that those minerals cannot be absorbed in the small intestine. An increase in the amount of iron and zinc in the cereals may overcome this problem. Through breeding strategies, new varieties of cereals can be produced that have higher iron and zinc concentrations. We tested the availability of iron and zinc from those higher mineral cereals in a group of college-aged women who had low iron stores. The increased amount of iron and zinc only allowed the women to absorb a little more iron and zinc. The increase was too small to overcome the negative effects of phytate and to improve iron and zinc nutrition.
Technical Abstract: Iron and zinc deficiencies are common in populations dependent on cereal- based diet due to the poor bioavailability of these minerals in those foods. Selective breeding of high mineral grains can improve the total intake of iron and zinc. However, the additional iron and zinc from those grains may not be available for absorption due to the high phytate content of cereals. Iron and zinc bioavailability needs to be measured before the high mineral crops are promoted. Iron or zinc bioavailability can be measured from: 1) the response of a physiological variable, 2) assessment of body retention, 3) tissue or blood uptake, 4) changes in pool size, or 5) rates of absorption. Iron bioavailability is preferentially measured from erythrocyte uptake of an oral radio or stable iron tracers; zinc bioavailability is measured from the rate of absorption of an oral isotopic tracer compared to an intravenous tracer. The oral label, required for studies of both iron and zinc, may be intrinsically labeled in the plant during growth or extrinsically added prior to feeding. Iron and zinc bioavailability from intrinsically-and extrinsically-labeled normal- and high-mineral common bean varieties was tested in young women with low iron stores. The absorption of intrinsic and extrinsic labels of iron and zinc did not differ. The bioavailability of iron and zinc from both varieties was low, about 1.5 and 13%, respectively. Methods to improve the bioavailability of iron and zinc from plant foods need to be developed.