EFFECT OF MENSTRUAL-CYCLE PHASE ON THE CONCENTRATION OF INDIVIDUAL CAROTENOIDS IN LIPOPROTEINS OF PREMENOPAUSAL WOMEN - A CONTROLLED DIETARY STUDY

Because premenopausal women experience cyclic fluctuations of plasma c arotenoids and their lipoprotein carriers, it is hypothesized that car otenoid concentrations in lipoprotein fractions fluctuate by phase of the menstrual cycle. Nine women ate a standard set of carotenoid-rich foods daily for two cycles under isoenergetic conditions. In the secon d cycle, hormones and carotenoids in lipoprotein fractions were measur ed in the early and late follicular and luteal phases. alpha-Carotene concentrations in the LDL fraction were lower in the early than in the late follicular phase (P = 0.03) on the basis of regression analysis. beta-carotene concentrations in the LDL fraction and the HDL2 subfrac tion were higher in the late follicular than in the luteal phase (P = 0.02 and P = 0.04, respectively). Lutein/zeaxanthin concentrations in the LDL and HDL fractions were higher in the late follicular than in t he luteal phase (P = 0.03 and P = 0.02, respectively). In each phase, 80% of alpha-carotene, 82% of beta-carotene, 85% of lycopene, and 64% of lutein/zeaxanthin were distributed in the LDL fraction. Among the h ydrocarbon cartenoids, 18% of alpha-carotene and of beta-carotene and 13% of lycopene were distributed in the HDL fraction, with slightly mo re in the HDL2 than in the HDL3 subfraction. In contrast 34% of lutein /zeaxanthin was distributed in the HDL fraction with more concentrated in the HDL3.than in the HDL2 subfraction. Less than 4% of any caroten oid was found in the VLDL+IDL (intermediate-density-lipoprotein) fract ions. Thus, the hydrocarbon carotenoids were highly concentrated in th e LDL fraction and xanthophyll was more evenly distributed in the LDL and HDL fractions. The cyclic fluctuations of these carotenoids in lip oprotein fractions add another dimension to the understanding of their transport and physiologic function.