THE FLUCTUATION OF PLASMA CAROTENOID CONCENTRATIONS BY PHASE OF THE MENSTRUAL-CYCLE - A CONTROLLED DIET STUDY

This is the first controlled diet study to examine the fluctuation of plasma carotenoids, lipoproteins, and serum hormone concentrations by phase of the menstrual cycle. Nonsmoking, premenopausal women (n = 12) with confirmed ovulatory cycles were given a standard diet with 10 mg total carotenoids/d for two cycles under isoenergetic conditions. Blo od was drawn for simultaneous measurement of carotenoids, lipoproteins , and hormones on menses days 1-2, 4-6, 11 through 1 d after the lutei nizing hormone surge, and 7-8 d after the surge, representing the mens es, early and late follicular, and midluteal phases, respectively. Reg ression modeling with adjustment for plasma cholesterol concentrations was used to compare mean individual and total plasma carotenoid conce ntrations by phase of the cycle. Plasma carotenoid concentrations were at their lowest at menses and significantly higher thereafter, except for a-carotene. Compared with plasma concentrations at menses, p-caro tene peaked (increased by 9%, P = 0.01) in the late follicular phase. Plasma lutein/zeaxanthin and anhydrolutein concentrations were higher by 8-11% (P less than or equal to 0.006) and by 15-31% (P less than or equal to 0.02), respectively, during the last three phases. Plasma ly copene and phytofluene concentrations peaked (increased by 12%, P = 0. 004; and by 21%, P = 0.006, respectively) at the midluteal phase. This cyclic fluctuation may affect the estimation of the plasma carotenoid -disease relation in studies of premenopausal women.