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Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions

Sweet Potato β-Carotene Bioefficacy Is Enhanced by Dietary Fat and Not Reduced by Soluble Fiber Intake in Mongolian Gerbils^1,2

³ Interdepartmental Graduate Program in Nutritional Sciences, University of Wisconsin, Madison, WI 53706; ⁴ Department of Food Science and Technology, Makerere University, Kampala, Uganda; ⁵ International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh 1212; and ⁶ Interdisciplinary Ph.D. Program in Nutrition, and ⁷ Department of Human Nutrition, The Ohio State University, Columbus, OH 43210

Orange-fleshed sweet potato (OFSP) is an important source of β-carotene (βC). Provitamin A bioefficacy from plant foods is influenced by dietary fat and fiber. We fed 3% OFSP powder diets with varying amounts of fat and soluble fiber to vitamin A (VA)-depleted Mongolian gerbils (n = 85) for 3 wk (8 groups, n = 10/group; control, n = 9) following a baseline kill (n = 6). OFSP diets differing in fat (3, 6, and 12%) contained 0.24% soluble fiber. Two additional 3% OFSP diets contained 6% fat and 3 or 9% white-fleshed sweet potato (WFSP) powder with soluble fiber contents of 0.42 and 0.80%, respectively. Control, VA-, and βC-supplemented groups were included. Simulated digestion experiments compared the bioaccessibility of βC from boiled vs. oil stir-fried OFSP. All OFSP diets maintained VA status and 12% fat and WFSP-added diets improved VA status above baseline (P < 0.05). Bioefficacy, as bioconversion factors, in gerbils fed 12% fat (3.5 ± 1.4 µg βC:1 µg VA) was improved over the 3% fat and βC groups (6.5 ± 3.7 and 6.7 ± 3.7 µg βC:1 µg VA, respectively) (P < 0.05) but did not differ from WFSP-added groups or the 6% fat group with no WFSP. Stir-frying doubled the efficiency of βC incorporation into micelles during small intestinal digestion in support of the stimulatory effect of dietary fat on bioefficacy in vivo. Soluble fiber intake derived from WFSP did not influence bioefficacy. Replacing WFSP with OFSP will affect VA status if adopted by target groups.

^* To whom correspondence should be addressed. E-mail: sherry{at}nutrisci.wisc.edu.

Manuscript received 25 August 2008. Initial review completed 1 October 2008. Revision accepted 22 October 2008.

Published online 3 December 2008.