Objectives: This study combined multiple sources of vitamin A in an animal to determine the effect on liver concentrations. Many countries are now combining vitamin A interventions in the same population groups. This increases the risk of excessive stores of vitamin A.
Methods: The study design was a 2x2x2 factorial with maize (orange vs. white) by carrot (orange vs. white) by preformed vitamin A fortificant (VA+ vs. VA-) in male Mongolian gerbils (n = 85). The study included a 14-d vitamin A-depletion period followed by a 62-d treatment period (8 treatments, n = 10/treatment). Total retinol from liver and serum was quantified by HPLC.
Results: Treatments significantly affected liver retinol concentrations (P < 0.0001), but did not affect serum retinol concentrations (P > 0.05). The vitamin A fortificant was not able to maintain baseline liver reserves, but did prevent vitamin A deficiency, defined as < 0.1 micromole/g liver. Orange maize maintained baseline liver retinol concentrations. The groups that were fed orange carrot all had similar liver retinol concentrations (~0.7 micromole/g liver). Therefore, the vitamin A level in the liver was maintained even though a wide difference in provitamin A carotenoids was fed. beta-Carotene concentrations revealed a dose response.
Conclusions: It appears that a liver reserve concentration of 0.7 micromole/g liver mitigates further bioconversion of provitamin A carotenoids beyond requirements. Historically, this level was considered excessive. This is the first study to show that this liver reserve has a biological negative impact on bioconversion of provitamin A carotenoids.