Iron bioavailability from Amaranthus species: 2—Evaluation using haemoglobin repletion in anaemic rats

Initial screening of 46 lines from 12 species of Amaranthus indicated wide variation in total iron (Fe) and small but significant differences in bioavailable Fe when estimated by an in vitro assay. To verify if differences in bioavailable Fe detected by in vitro assay were biologically significant, one line from each species A tricolor, A hypochondriacus and A cruentus was evaluated using a haemoglobin (Hb) repletion assay with anaemic rats. Anaemic rats were fed treatment diets in which almost all Fe was provided by amaranth lines, and Hb gains were compared to those of rats fed control FeSO₄ diets. Slope ratio analysis indicated that Fe supplied by A hypochondriacus had a greater relative bioavailability (61%) than from A tricolor (44%), when compared to FeSO₄ (100%). However, A tricolor contained a higher concentration of total Fe (690 ppm) in the leaf material. When the same amount of amaranth was added to individual diets (30 g kg⁻¹ diet), analysis of Hb repletion efficiency (HRE) indicated that A tricolor supported the largest Hb gain of the three lines, despite having the lowest relative bioavailability compared to A hypochondriacus and A cruentus. Despite a lack of correlation between total and bioavailable Fe, these results suggest future efforts should focus initially on enhancing total Fe concentration of green leafy vegetables (GLVs), until the forms of bioavailable Fe in these plant materials are identified. Rat bioassay did confirm relative differences in bioavailable Fe estimated by the in vitro assay, supporting use of the in vitro assay in breeding programmes focused on improving Fe nutritional quality of GLVs. © 1998 Society of Chemical Industry