Higher iron pearl millet (Pennisetum glaucum L.) provides more absorbable iron that is limited by increased polyphenolic content

BACKGROUND: Our objective was to compare the capacity of iron (Fe) biofortified and standard pearl millet (Pennisetum glaucum L.) to deliver Fe for hemoglobin (Hb)-synthesis. Pearl millet (PM) is common in West-Africa and India, and is well adapted to growing areas characterized by drought, low-soil fertility, and high-temperature. Because of its tolerance to difficult growing conditions, it can be grown in areas where other cereal crops, such as maize, would not survive. It accounts for approximately 50% of the total world-production of millet. Given the widespread use of PM in areas of the world affected by Fe-deficiency, it is important to establish whether biofortified-PM can improve Fe-nutriture. METHODS: Two isolines of PM, a low-Fe-control (“DG-9444”, Low-Fe) and biofortified (“ICTP-8203 Fe”,High-Fe) in Fe (26 μg and 85 μg-Fe/g, respectively) were used. PM-based diets were formulated to meet the nutrient requirements for the broiler (Gallus-gallus) except for Fe (Fe concentrations were 22.1±0.52 and 78.6±0.51 μg-Fe/g for the Low-Fe and High-Fe diets, respectively). For 6-weeks, Hb, feed-consumption and body-weight were measured (n = 12). RESULTS: Improved Fe-status was observed in the High-Fe group, as suggested by total-Hb-Fe values (15.5±0.8 and 26.7±1.4 mg, Low-Fe and High-Fe respectively, P<0.05). DMT-1, DcytB, and ferroportin mRNA-expression was higher (P<0.05) and liver-ferritin was lower (P>0.05) in the Low-Fe group versus High-Fe group. In-vitro comparisons indicated that the High-Fe PM should provide more absorbable-Fe; however, the cell-ferritin values of the in-vitro bioassay were very low. Such low in-vitro values, and as previously demonstrated, indicate the presence of high-levels of polyphenolic-compounds or/and phytic-acid that inhibit Fe-absorption. LC/MS-analysis yielded 15 unique parent aglycone polyphenolic-compounds elevated in the High-Fe line, corresponding to m/z = 431.09. CONCLUSIONS: The High-Fe diet appeared to deliver more absorbable-Fe as evidenced by the increased Hb and Hb-Fe status. Results suggest that some PM varieties with higher Fe contents also contain elevated polyphenolic concentrations, which inhibit Fe-bioavailability. Our observations are important as these polyphenols-compounds represent potential targets which can perhaps be manipulated during the breeding process to yield improved dietary Fe-bioavailability. Therefore, the polyphenolic and phytate profiles of PM must be carefully evaluated in order to further improve the nutritional benefit of this crop.