Julie Howe, Auburn University, 201 Funchess Hall, Auburn, AL 36849 and Sherry A. Tanumihardjo, University of Wisconsin-Madison, 1415 Linden Dr., Madison, WI 53706.
In many areas of the world, vitamin A (VA) deficiency is a major health problem. Staple foods such as maize, rice, cassava, and wheat, are typically low in provitamin A. Recent efforts to genetically improve cassava with provitamin A carotenoids, e.g., β-carotene, have been successful, but whether this approach alleviates VA deficiency has not been determined. Two studies investigated the bioefficacy of provitamin A carotenoids from cassava and compared the effects of cassava percentage and carotenoid content on VA status in VA-depleted Mongolian gerbils (Meriones unguiculatus). Three near-isogenic cassava lines were used to prepare 6 feeds with variable carotenoid compositions. To deplete stored VA, gerbils were fed a white cassava VA-free diet for 4 wk. In study 1, treatments (n = 10 per group) included 45% high-β-carotene cassava, β-carotene and VA supplements (pair-fed to high-β-carotene maize), and oil control. In study 2, gerbils (n ~ 10 per group) were fed ~30% or ~15% of two different cassava varieties. After the 4-wk treatment phase, serum and liver VA were determined. For study 1, total liver VA was significantly higher in the VA group, lower in the control, and did not differ from the β-carotene supplement or baseline groups when compared with the high-β-carotene cassava group. On a β-carotene basis, bioconversion was ~4:1 (mg β-carotene:1 mg VA) in the high β-carotene cassava and ~3:1 in the β-carotene supplement group. Liver β-carotene was present in the high β-carotene cassava and β-carotene supplement groups. Storage of β-carotene, rather than conversion to VA, indicates gerbils had adequate VA. Study 2 showed no significant difference in liver VA regardless of diet, but stored β-carotene was greater in gerbils receiving the ~30% cassava diets compared to the ~15% diet. Biofortified cassava adequately maintained VA status in this model and was as effective as β-carotene supplementation.