Seed Coat Removal Improves Iron Bioavailability in Cooked Lentils: Studies Using an in Vitro Digestion/Caco-2 Cell Culture Model

Abstract

In this study we examined the range of Fe concentration and relative Fe bioavailability of 24 varieties of cooked lentils, as well as the impact of seed coat removal on Fe nutritional as well as antinutrient properties. Relative Fe bioavailability was assessed by the in vitro/Caco-2 cell culture method. While the Fe concentration of the whole lentil was moderately high (72.8 ± 10.8 μg/g, n = 24), the relative Fe bioavailability was moderate (2.4 ± 1.0 ng of ferritin/mg of protein). Although removing the seed coat reduced the Fe concentration by an average of 16.4 ± 9.4 μg/g, the bioavailability was significantly improved (+5.3 ± 2.2 ng of ferritin/mg of protein; p < 0.001), and the phytic acid concentration was reduced by 7% (p = 0.04). Like most legume seeds, the lentil seed coat contains a range of polyphenols known to inhibit Fe bioavailability. Thus, along with breeding for high Fe concentration and bioavailability (i.e., biofortification), seed coat removal appears to be a practical way to improve Fe bioavailability of the lentil.