A sustainable solution to dietary iron deficiency can be achieved in part by increasing bioavailable iron in seeds used for food such as soybeans. Dietary iron deficiency and anemia afflict 1.5 billion people world-wide, approximately 6.6 percent of women of reproductive age and approximately 11 percent of children and adolescents in the U.S. are affected. Since ferritin is used as a natural source of iron in the early development of humans, other animals, and plants, the availability of iron in soybean seeds that are rich in ferritin was tested in iron deficient rats. Soybeans were selected for study because of the naturally high iron levels, a variety of readily accessible cultivars, the large consumption world-wide including, recently, in the United States. Measuring bioavailability of ferritin iron has recently shown that horse spleen ferritin and soybean meal ferritin from iron-rich soybean cultivars can cure nutritional iron deficiency at amounts of iron equivalent to ferrous sulfate. Diets were equivalent for carbohydrate, protein, and fat. Recovery from anemia was measured by hematocrit, hemoglobin concentration, and tissue (spleen, liver, brain) iron concentrations. The results contrast with those obtained previously with labelled Fe, in part because of new knowledge which shows (a) a slow equilibration of the isotopically labeled iron (1-2 years); (b) coexistence of ferritin with in vivo in pools with distinctive labeling; (c) that extrinsically added iron labels only approximately 0.1 percent of the ferritin iron; and (d) that protocols for intrinsically labelled iron likely produced a stress ferritin which can have slow iron turnover. Preliminary data show that soybean seed ferritin concentrations are cultivar specific, that nodule iron is recycled to provide approximately 41 percent seed iron, accounting at least in part for the high concentration of iron in legume seeds, and that much of the iron in soybean seeds is in ferritin. In order to further understand the relationship between seed ferritin and bioavailable iron, experiments in iron-deficient and iron-sufficient humans are proposed to analyze: (1) The utilization of soybean ferritin iron from soy flour or tofu or broth; the effect of ascorbate and phytate on absorption will be determined as well to evaluate the influence of inhibitors and enhancers. (2) The effect of soybean processing on retention of soybean ferritin. If time permits, the ferritin promotor and seed ferritin will be analyzed in crosses of cultivars with high and low amounts of ferritin and soluble iron to allow future development of soybeans with enhanced amounts of iron that can contribute to a sustainable solution to iron deficiency in humans.
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