Abstract
BackgroundOur objective was to determine if a biofortified variety of black bean can provide more bioavailable-iron (Fe) than a standard variety. Two lines of black beans (Phaseolus-vulgaris L.), a standard (DOR500; 59μg Fe/g) and biofortified (MIB465; 88μg Fe/g) were used. The DOR500 is a common commercial variety, and the MIB465 is a line developed for higher-Fe content. Given the high prevalence of Fe-deficiency anemia worldwide, it is important to determine if Fe-biofortified black beans can provide more absorbable-Fe.MethodsBlack bean based diets were formulated to meet the nutrient requirements for the broiler (Gallus-gallus) except for Fe (dietary Fe-concentrations were 39.4±0.2 and 52.9±0.9 mg/kg diet, standard vs. biofortified, respectively). Birds (n=14) were fed the diets for 6-weeks. Hemoglobin-(Hb), liver-ferritin and Fe-related transporter/enzyme gene-expression were measured. Hemoglobin-maintenance-efficiency and total-body-Hb-Fe values were used to estimate Fe-bioavailability.ResultsHemoglobin-maintenance-efficiency values were higher (P<0.05) in the group consuming the standard-Fe beans on days 14, 21 and 28; indicating a compensatory response to lower dietary-Fe. Final total-Hb-Fe body content was higher in the biofortified vs. the standard group (26.6±0.9 and 24.4±0.8 mg, respectively; P<0.05). There were no differences in liver-ferritin or in expression of DMT-1, Dcyt-B, and ferroportin. In-vitro Fe-bioavailability assessment indicated very low Fe-bioavailability from both diets and between the two bean varieties (P>0.05). Such extremely-low in-vitro Fe-bioavailability measurement is indicative of the presence of high levels of polyphenolic-compounds that may inhibit Fe-absorption. High levels of these compounds would be expected in the black bean seed-coats.ConclusionsThe parameters of Fe-status measured in this study indicate that only a minor increase in absorbable-Fe was achieved with the higher-Fe beans. The results also raise the possibility that breeding for increased Fe-concentration elevated the levels of polyphenolic-compounds that can reduce bean Fe-bioavailability, although the higher levels of polyphenolics in the higher-Fe beans may simply be coincidental or an environmental effect. Regardless, Fe-biofortified beans remain a promising vehicle for increasing intakes of bioavailable-Fe in human populations that consume high levels of these beans as a dietary staple, and the bean polyphenol profile must be further evaluated and modified if possible in order to improve the nutritional quality of higher-Fe beans.
Highlights
Iron (Fe) deficiency is the most common nutrient deficiency worldwide [1]
Hemoglobin (Hb), Hb Hemoglobin iron (Fe) and Hb maintenance efficiency (HME) There were no significant differences in feed intakes at any time throughout the study; Fe intakes were consistently higher in the “Biofortified Fe” group vs. “Standard Fe” group
Significant differences were measured in hemoglobin maintenance efficiency (HME) on days 14, 21 and 28 of the experiment between the “Biofortified Fe” group vs. “Standard Fe” group (Figure 1)
Summary
Iron (Fe) deficiency is the most common nutrient deficiency worldwide [1]. Iron deficiency is widespread in low-income populations where consumption of meat is low and consumption of cereal grains and legumes which contain inhibitors of iron absorption make up the bulk of a diet with little diversity [2,3,4,5,6,7]. This strategy is known as biofortification [16] In theory, this effort is expected to improve the Fe status of humans in developing countries as it utilizes the tools of plant breeding and agriculture to enhance the amount of absorbable Fe in staple food crops. This effort is expected to improve the Fe status of humans in developing countries as it utilizes the tools of plant breeding and agriculture to enhance the amount of absorbable Fe in staple food crops Once these lines have been developed and stabilized for traits such as higher Fe concentration and or higher Fe bioavailability, the nutritional benefits should be driven and provided by agriculture and sustainable in terms of cost and benefit. Given the high prevalence of Fe-deficiency anemia worldwide, it is important to determine if Fe-biofortified black beans can provide more absorbable-Fe
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