FOOD INTERACTIONS AND FACTORS THAT AFFECT IRON BIOAVAILABILITY FROM BEANS AND PEARL MILLET
Plant, Soil and Nutrition Research
2012 Annual Report
1a.Objectives (from AD-416):
We will determine how other foods commonly consumed in combination with beans or pearl millet affect the iron (Fe) bioavailability and absorption of the overall meal. Food interactions will be based on common combinations of targeted countries of Latin America, Asia, and Africa.
1b.Approach (from AD-416):
We will use a combination of in vitro screening coupled with in vivo long term feeding trials of poultry. We previously demonstrated that the chicken model exhibits the appropriate responses to iron (Fe) deficiency and can serve as a model for iron (Fe) bioavailability. These feeding trials will span up to 8 weeks depending on the observed effects of the test diets.
The focus of this project shifted from pearl millet to sorghum as collaborators in India were unable to provide us with samples. Transgenic sorghum samples supplied by Pioneer Seeds, engineered to be low in phytic acid (an inhibitor of Fe absorption) were evaluated using our initial cell culture (ie. in vitro) model and found to have improved Fe bioavailability, perhaps as much as 2-3 times that of control samples. However, polyphenolic compounds are high in sorghum, and strongly inhibit Fe bioavailability. Additional amounts of these lines were generated over the past year so that animal testing to confirm the previous in vitro results could be conducted. Evaluation of these larger amounts with our cell culture model indicates that the reduced phytate does improve Fe bioavailability; however, the bioavailability appears to be very low. When added to a poultry ration at a level of 75% no beneficial difference in Fe bioavailability was observed in the transgenic lines relative to the controls. Feeding the same diets to poultry also showed no beneficial effects. These results suggest that future research should be directed at increasing the Fe concentration in these lines and or reducing the polyphenolic compounds in order for these lines to have nutritional benefit.
High and normal Fe black beans, generated by bean breeders at the International Center for Tropical Agriculture (CIAT) were sent to our lab for comparison of Fe bioavailability. These were the same exact lines that were used in a recent human feeding trial in Mexico. Preliminary results from our animal studies indicate that the high Fe black beans provided more Fe relative to the normal beans. More complete analysis of the results and tissue analysis of the animals are pending. These results are promising for biofortification; however, the seed coat polyphenols of black beans are potent inhibitors of Fe absorption and pose a serious challenge to Fe biofortification of this crop. Additional studies to understand the precise polyphenols in the seed coat that inhibit Fe absorption are warranted.