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United States Department of Agriculture

Agricultural Research Service


Location: Plant, Soil and Nutrition Research

2011 Annual Report

1a.Objectives (from AD-416)
Objective 1. Determine the genes affecting iron level and bioavailability in edible portions of maize by utilizing quantitative trait loci (QTL) mapping and an in-vitro digestion/Caco-2 cell culture model system. Confirm this QTL information via in-vitro and in-vivo studies and transfer this information to plant breeders. Objective 2. Investigate the role and mechanisms of action of prebiotic compounds, beneficial bacteria, and plant phenolic constituents on the bioavailability of iron and zinc from the diet.

1b.Approach (from AD-416)
This project seeks to improve the bioavailability of iron (Fe) and zinc (Zn) in plant foods by two distinct strategies. First, a multidisciplinary, genomics-based approach will be used to identify the genes and chemical factors that modulate Fe bioavailability in maize grain, using maize as the model to demonstrate proof of concept for this work. The second approach defines how prebiotic (non-digestible carbohydrates) and polyphenolic compounds in plant foods influence Fe and Zn bioavailability and thereby enhance absorption of Fe and Zn from plant foods in the intestine. Maize Fe Bioavailability: The goal here is to improve the nutritional quality of maize with respect to Fe via identifying the genetic factors that contribute to improved seed-iron concentration and bioavailability. This will be accomplished by building on current genetic mapping of maize seed-Fe bioavailability using a simulated intestinal digestion/Caco-2 cell assay. Animal models will then be used to confirm the cell culture results before definitive testing in humans. By identifying the genes that contribute to seed-iron accumulation and bioavailability, plant breeders will be able to improve the nutritional quality of maize. Prebiotics, Beneficial Bacteria, Polyphenols and Fe/Zn Bioavailability: The gastrointestinal microflora is increasingly becoming recognized as a major factor in human health via systemic effects on gut health and nutrient absorption. Prebiotic compounds such as inulin dramatically alter the profile of intestinal microflora and this alteration may enhance absorption of Fe and Zn. Therefore, one of the goals here is to determine if prebiotics enhance Fe and Zn absorption via changes in gut microflora. The second subobjective is to determine if polyphenolic compounds play a significant role in Fe absorption in long term feeding trials. This will be accomplished via animal feeding trials and cell culture models, whereby foods will be compared that have low and high amounts of prebiotics (eg. inulin, raffinose, stachyose) and polyphenols (e.g., kaempferol, quercitin, chlorogenic acid, ferulic acid). In these studies Fe and Zn absorption from these foods will be measured, as well as their effect on the bacterial profile. By understanding the role of prebiotics and polyphenols in the absorption of these two essential minerals, plant foods and food products can be improved to provide more optimal nutrition.

3.Progress Report
Progress was made on Objective 1 of the research plan which is under NP107. We have identified regions of the maize genome where genes reside that influence maize seed Fe bioavailability. In other words, we developed maize with high and low bioavailable Fe in the kernels and successfully tested these varieties three times in poultry. On all occasions the birds fed the “high” bioavailable Fe maize maintained their Fe status at a level significantly higher than those consuming the “low” bioavailable Fe maize. These varieties now warrant testing in human subjects for confirmation that the nutritional value of iron in the maize has been enhanced which is the objective of the national program component assigned to this project.

We are working to identify the compounds that account for the differences in the above-mentioned maize lines. This research has now been facilitated by the acquisition of a critical piece of equipment, specifically an LC mass spectrometer with state-of-the-art software capable of identifying the compounds or metabolites in the maize seed that are related to Fe bioavailability. Our research personnel have been training on how to use this instrument over the past year and are applying it to this research objective.

We have also studied the Fe bioavailability of lentils. We were able to demonstrate that increasing the iron concentration in lentils can provide nutritional benefits. For example, in both a cell culture model and a poultry feeding trial, we studied 3 lentil varieties that differed in their iron concentrations (varieties tested had 55, 75 and 95 µg Fe/g seed). In a 4 week poultry feeding trial, iron deficient broiler chickens that were given a 40% lentil diet showed improvement in their iron status that was consistent and proportional to the lentil iron concentrations. These observations are important as lentil is a common crop that is widely consumed in areas where people suffer from dietary iron deficiency.

In FY 2011, we participated in a human efficacy trial, testing the effect of high black beans on iron status in children in Mexico. This work was a collaboration with scientists from Cornell University, the International Center for Tropical Agriculture (CIAT) in Cali, Colombia, the National Institute of Health in Mexico, and the organization known as HarvestPlus, in Washington, DC. This research shows promise that increasing the iron concentration in black beans can provide additional Fe to resource poor children in Mexico; however, this promising result was not a strong difference likely due to unexpected complications in performing human efficacy trials in this relatively remote region.

Prebiotics such as inulin have been shown to increase mineral absorption. Using chicken eggs during the last few days of incubation, and using the hatched chicks, we have demonstrated that intra amniotic administration and dietary inulin have improved the iron status of iron deficient broiler chicks. Furthermore, we have been able to show that this occurs via increased Fe absorption in the intestine. These results are encouraging as it implies that similar results should occur in humans consuming prebiotics.

1. ARS researchers at the Robert W. Holley Center at Ithaca, NY, demonstrated that addition of a prebiotic (inulin) improves poultry health and growth rate. Prebiotics such as inulin are known to improve health and growth rate in almost all animals including humans. Our research has shown that these benefits can extend to poultry, specifically broiler chicks where early health and growth can be beneficial to poultry producers. Injection of substances into poultry eggs is already practiced in the poultry industry; thus the addition of a prebiotic injection could be easily incorporated into industry practices. In regards to humans and animal health, this research further confirms the benefits and mechanism of action of probiotic on gut health and nutrient absorption.

2. High Fe lentils alleviated Fe deficiency in poultry. Iron deficiency affects a third of the world’s population, mostly those consuming staple food crops that are relatively low in Fe as a major part of their diet. In cooperation with the Saskatchewan Pulse Growers Association and the University of Saskatchewan, Saskatoon, Canada, ARS researchers at the Robert W. Holley Center at Ithaca, NY, have identified that high Fe lentils are produced and processed in this region. Moreover we have shown that these high Fe lentils can produce nutritional benefits in poultry, suggesting that similar effects should be seen in Fe deficient humans. A large scale human efficacy study is now being planned to test the effect of high Fe lentils in humans in Bangladesh. This is the first research effort and collaboration that has established a location and grower association capable of producing a biofortified crop via sustainable modern agricultural practices.

Review Publications
Glahn, R.P. 2009. The use of caco-2 cells in defining nutrient bioavailability: application to iron bioavailability of foods. In: McClements, D., Decker, E. Designing functional foods: measuring and controlling food structure breakdown and nutrient absorption. Cambridge, UK: Woodhead Publishing Limited. p. 340-361.

Lung'Aho, M.G., Glahn, R.P. 2010. Use of White Bean Instead of Red Bean May Improve Iron Bioavailability from a Tanzanian Complementary Food Mixture. International Journal for Vitamin and Nutrition Research. 80(1):24-31.

Mcauliffe, G.J., Chang, J., Glahn, R.P., Shuler, M.L. 2008. Development of a gastrointestinal tract microscale cell culture analog to predict drug transport. Molecular and Cellular Biomechanics. 5(2):119-132.

Last Modified: 4/23/2014
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