Comparison of bioavailability of the vitamin A-forming carotinoids (beta-cryptoxanthin. beta-carotene and alpha-carotene).

Beta‐carotene (BC), beta‐cryptoxanthin (CX) and alpha‐carotene (AC) are common vitamin A (VA)‐forming carotenoids in human diets and blood. Recently conversion ratios for VA formation were set at 12:1, 24:1, and 24:1 for BC‐, CX‐ and AC‐rich foods, respectively. The conversion ratio for BC is based on scientific data of its bioavailability, but ratios for CX‐ and AC‐rich foods are based primarily on the chemical structure of these carotenoids without regard for their bioavailability from their primary food sources. However, in our studies CX serum concentrations have been unexpectedly high compared to dietary intakes. We hypothesized that CX serum concentrations might also be elevated compared to dietary intake in other studies. We calculated the ratio of dietary intake to serum concentration for AC, BC, and CX from our studies and several large US and European surveys. We then compared the ratios of AC/BC and CX/BC. The ratio of AC/BC approached 1 (AC/BC = 0.74 to 1.1), suggesting that eating similar amounts of AC‐ and BC‐rich foods result in similar blood concentrations, and thus that the primary food sources of AC and BC have comparable bioavailability. However, the ratio of CX/BC was 5.6 to 35, suggesting that eating comparable amounts of CX and BC resulted in much higher serum CX concentrations. This suggests that the bioavailability of CX from its main food sources is higher than BC or AC, and that CX‐rich foods might be better sources of VA than expected from their abundance in the diet.