Amount of dietary fat and type of soluble fiber independently modulate postabsorptive conversion of ss-carotene to vitamin A in mongolian gerbils

Current dietary guidelines recommend a decrease in fat intake and an increa se in fiber consumption. Decreased bioavailability (BV) of carotenoids is t hought to be associated with both of these recommendations. A 2 x 4 factori al design was used to test the effects of dietary fat level at 10 or 30% of total energy and fiber type using no fiber, silica, citrus pectin or oat g um (7 g/100 g) on beta -carotene (betaC) BV in 4- to 5-wk-old Mongolian ger bils. We assessed BV as both accumulation of PC and bioconversion of PC to vitamin A (VA) in tissues. A VA- and PC-deficient diet was fed for 1 wk fol lowed by one of eight isocaloric, semipurified diets supplemented with carr ot powder [similar to1 mug betaC, 0.5 mug alpha -carotene (alphaC)/kJ diet] for 2 wk (n = 12/group). Increasing dietary fat resulted in higher VA (P = 0.074) and lower PC (P = 0.0001) stores in the liver, suggesting that cons umption of high fat diets enhances conversion of PC to VA. The effect of so luble fiber on hepatic VA storage was dependent on fiber type. Consumption of citrus pectin resulted in lower hepatic VA stores and higher hepatic PC stores compared with all other groups, suggesting less conversion of PC to VA. In contrast, consumption of oat gum resulted in hepatic VA and betaC st ores that were higher (P = 0.012) and lower (P = 0.022), respectively, than those of citrus pectin-fed gerbils. The level of dietary fat consumed with soluble fiber had no interactive effects on hepatic VA, betaC or alphaC st ores. Results demonstrate that betaC BV is independently affected by dietar y fat level and type of soluble fiber, and suggest that these dietary compo nents modulate postabsorptive conversion of betaC to VA. This study confirm s the negative effects of citrus pectin on betaG BV, and suggests that oat gum does not adversely affect betaC BV.