BETA-CAROTENE SUPPLEMENTATION INCREASES ANTIOXIDANT CAPACITY OF PLASMA IN OLDER WOMEN

The antioxidant effect of dietary beta-carotene supplementation on the peroxidation potential of plasma was investigated in a randomized dou ble-blind, placebo-controlled study. Twelve healthy women (62-80 y) su pplemented their usual daily diet with 90 mg of beta-carotene (n = 6) or placebo (n = 6) capsules for 3 wk. Plasma concentrations of beta-ca rotene, alpha- and gamma-tocopherol, ascorbate, urate, bilirubin and i n vitro production of phosphatidylcholine hydroperoxides (PC-OOH) and utilization of plasma antioxidants in the presence of 50 mmol/L 2,2'-a zobis (2-aminopropane) hydrochloride (AAPH), a free radical generator, at 37 degrees C were measured before and after dietary treatment. Pla sma beta-carotene increased from 0.76 +/- 0.16 to 6.45 +/- 1.16 mu mol /L (P < 0.05) in supplemented but not placebo-treated subjects. The pl asma concentrations of other antioxidants did not change significantly in either group. beta-Carotene supplementation did not affect basal l evels of plasma PC-OOH as measured by HPLC postcolumn chemiluminescenc e but did affect AAPH-induced production of PC-OOH. Before supplementa tion, the induction period of plasma PC-OOH production was 2.4 +/- 0.4 h, with levels reaching 5.39 +/- 1.50 mu mol/L after 6 h of incubatio n. After supplementation, the induction period increased significantly to 4.2 +/- 0.4 h (P < 0.01), with a lower PC-OOH production of 2.16 /- 0.90 mu mol/L after 6 h (P < 0.05). In this system, plasma ascorbat e concentrations were depleted first, followed by loss of bilirubin an d alpha-tocopherol and then by the sequential loss of gamma-tocopherol , urate and beta-carotene. These results indicate that beta-carotene s upplementation increases the plasma antioxidant capacity of older wome n.