beta-carotene isomers in human serum, breast milk and buccal mucosa cells after continuous oral doses of all-trans and 9-cis beta-carotene

The concentrations of all-trans beta-carotene (tBC) and 9-cis beta-carotene (9cBC) isomers in serum, breast milk and buccal mucosa cells were determined after continuous oral doses as a simple, non-invasive method to determine whether differences in tissue uptake are important determinants of serum responses. Twelve healthy lactating women were recruited for a nonresidential study. On d 1, blood samples were obtained from fasting subjects for baseline concentrations of beta-carotene isomers. Over a 1-wk period, subjects were given either seven doses of a placebo (n = 4) or seven doses of naturally occurring BC (n = 8) derived from Dunaliella bardawil (64 mg tBC, 69 mg 9cBC). Subjects were instructed to consume a single beta-carotene dose along with a meal containing adequate fat each day for 1 wk, On d 2, 3, 5 and 8, blood samples and breast milk were collected from fasting subjects. On d 1 and 8, buccal mucosa cells were collected. Samples were analyzed for carotenoids by HPLC. In the experimental group, the mean serum concentration of tBC significantly increased to seven times the baseline level by the end of the supplementation period (P < 0.0001). The serum concentration of 9cBC significantly increased to three times the baseline level by the end of the supplementation period (P < 0.0001). The changes in milk and buccal mucosa cells levels of tBC and 9cBC followed a pattern similar to that for serum, showing significant increases at the end of the supplementation period. In the control group, the serum, milk and buccal mucosa cell concentrations of BC isomers did not change. This study confirms the previously reported differences in the serum response curves of tBC and 9cBC and provides evidence that there is no difference in tissue uptake of tBC and 9cBC.