Biofortified Pearl Millet (Pennisetum glaucum L.) Provides More Bioavailable Iron than Standard Pearl Millet: Studies In vivo (Gallus gallus) and an In vitro Digestion/Caco-2 Model

Abstract

Objectives: Pearl millet (Pennisetum glaucum L.) is the most widely grown type of millet, primarily in Africa and India. Our objective was to compare the capacities of two isolines of pearl millet (standard and Fe biofortified) to deliver iron (Fe) for hemoglobin (Hb) synthesis. Methods: In-vitro analysis indicated that the biofortified line should provide more Fe (P<0.05), and indicate the presence of high levels of polyphenolic compounds that inhibit Fe-absorption. Pearl millet based diets (75% w/w) were formulated except for Fe (dietary Fe concentrations were 22.1±0.5 and 78.6±0.5μg/g) to be tested in-vivo (Gallus gallus). Diets were fed for 6 weeks; Hb, liver ferritin and Fe-related transporter/enzyme gene-expression were measured. Hb-maintenance efficiency (HME) and total body Hb-Fe values were used to estimate Fe-bioavailability from the diets. Results: From week 5 onward, Hb values were higher (P<0.05) in biofortified group vs. standard. Final total Hb-Fe content was higher in the biofortified vs. the standard  (26.7±1.4 and 15.5±0.8 mg, respectively) groups (P<0.05). DMT-1, Dcyt-B, and ferroportin expressions were higher and liver ferritin was lower (P<0.05) in the standard group vs. the biofortified group, indicating adaptive response to Fe-deficiency. Conclusions: We conclude that the biofortified pearl millet diet delivered more absorbable Fe and thus represents a promising vehicle for increasing intakes of bioavailable Fe in human populations that consume this dietary staple. In vitro studies indicate that a strong polyphenolic inhibitory effect on Fe-bioavailability is evident; thus further research into improving the nutritional content of pearl millet should involve assessment and if possible modification of the polyphenolic profile.