Cassava with enhanced β-carotene maintains adequate vitamin A status in Mongolian gerbils (Meriones unguiculatus) despite substantial cis-isomer content

Abstract

Efforts to increase-β-carotene in cassava have been successful, but the ability of high-β-carotene cassava to prevent vitamin A deficiency has not been determined. Two studies investigated the bioefficacy of provitamin A in cassava and compared the effects of carotenoid content and variety on vitamin A status in vitamin A-depleted Mongolian gerbils (Meriones unguiculatus). Gerbils were fed a vitamin A-free diet 4 weeks prior to treatment. In Expt 1, treatments (ten gerbils per group) included 45% high-β-carotene cassava, β-carotene and vitamin A supplements (intake matched to high - carotene cassava group), and oil control. In Expt 2, gerbils were fed cassava feeds with 1.8 or 4.3nmol provitamin A/g prepared with two varieties. Gerbils were killed after 4 weeks. For Expt 1, liver vitamin A was higher (P<005) in the vitamin A (1.45 (sd 0.23) μmol/liver), lower in the control (0.43 (sd 0.10) mol/liver), but did not differ from the β-carotene group (0.77 (sd 0.12) mol/liver) when compared with the high-β-carotene cassava group (0.69 (sd 0.20) μmol/liver). The bioconversion factor was 3.7μg β-carotene to 1 μg retinol (2mol:1mol), despite 48% cis-β-carotene [(Z)-β- carotene] composition in cassava. In Expt 2, cassava feed with 43nmol provitamin A/g maintained vitamin A status. No effect of cassava variety was observed. Serum retinol concentrations did not differ. β-Carotene was detected in livers of gerbils receiving cassava and supplements, but the cis-to-trans ratio in liver differed from intake. Biofortified cassava adequately maintained vitamin A status and was as efficacious as β-carotene supplementation in the gerbil model.