2007 Annual Report 1a.Objectives (from AD-416) To utilize in vitro and in vivo models of Fe and Zn bioavailability to screen select micronutrient-dense staple food crops (rice, wheat, maize, beans, sweet potato, and cassava) and identify those varieties that have high Fe and Zn bioavailability. In addition, these models will be used to investigate diet and food ingredient interactions that influence bioavailability of these minerals. 1b.Approach (from AD-416) We propose to use a two-tiered approach in the evaluation of the bioavailability of Fe and Zn in select micronutrient-dense staple plant food genotypes under development in this project. First, we will employ the in vitro Caco-2 cell model to screen large numbers of promising micronutrient-dense genotypes of staple plant food crops for bioavailable Fe. Then, after using this approach to identify promising, Fe-enriched genotypes, we will employ a pig model to evaluate both Fe and Zn bioavailability in each select genotype in the context of whole diets typical of each reference region of the project. Samples that show promise in this collaborative research can then be advanced for human trials with other collaborators of the Harvest Plus program. 3.Progress Report This report serves to document research conducted under a General Assistance Type Cooperative Agreement between ARS and the Department of Food Science at Cornell University. Additional details of research can be found in the report for the parent project 1907-42520-003-00D, “Understanding Soil-Plant-Human/Animal Food Systems and Nutrient Bioavailability to Improve Human Health.” To monitor progress on this project, frequent meetings, emails and telephone conversations were used. Studies conducted to determine the adequacy of extrinsic radiolabeling of bean Fe, indicated that extrinsic radiolabels did not equilibrate completely with the intrinsic Fe in the bean. This observation implies that the more costly method of intrinsic isotope labeling of bean Fe is needed to accurately evaluate Fe bioavailability from beans. The bioavailability of Fe in the ferritin form was evaluated in a simulated digestion/cell culture model and found not to be a form of Fe with enhanced bioavailability. Ferritin was degraded in the acid pH of the stomach and digestive enzymes thus releasing iron from ferritin in the inorganic form. Legume seeds store significant amounts of Fe as ferritin but the bioavailability of ferritin-Fe is in question. In agreement with human studies, in vitro studies demonstrated that ferritin Fe bioavailability is the same as FeSO4. In addition, ferritin-Fe is released during digestion at the low pH of the stomach contents and interacts with dietary Fe inhibitors and promoters similar to FeSO4. These results indicate that ferritin Fe is not a promoter of Fe bioavailability. Approximately 160 maize samples were received from collaborators at CIMMYT in Mexico. The objective was to determine the degree that genotype by environment interaction affect Fe bioavailability. It is important to know relative effects of this interaction on this nutritional trait as it may overwhelm the effect that can be introduced by genotype alone. Cassava samples were also received from the International Institute of Tropical Agriculture (IITA) and from CIAT and evaluated for Fe concentration and bioavailability. IITA samples were not high in Fe concentration and did not show a diverse range of Fe concentration and bioavailability. CIAT samples appeared to be higher in Fe and have more bioavailable Fe.