Estimating the concentration of β-carotene required for maximal protection of low-density lipoproteins in women

The reportedly inconsistent antioxidant protective effect of beta-carotene on plasma LDL may depend on LDL's beta-carotene concentration. We measured carbonyl production by CuSO4-challenged LDL from nine healthy women living at the US Department of Agriculture-Western Human Nutrition Research Center and consuming a natural food diet that provided only 0.14 mu mol beta-carotene/d for 120 d. During the first 60 d, four women received a placebo and the remaining five women received too small a supplement (0.93 mu mol beta-carotene/d) to increase plasma or LDL beta-carotene; therefore, the data for all nine women during this time were pooled. From days 61 to 120, all subjects received the small supplement. From days 101 to 120 they all received an additional, larger, mixed carotenoid supplement (6.16 mu mol beta-carotene/d), Plasma beta-carotene dropped from 0.76 +/- 0.21 mu mol/L ((x) over bar +/- SEM) on day 2 to 0.33 +/- 0.08 on day 60 (P = 0.035) and rose to 1.73 +/- 0.18 (P = 0.001) on day 120. LDL beta-carotene dropped from 1.67 +/- 0.53 mu mol/g LDL protein on day 2 to 1.27 +/- 0.28 mu mol/g LDL protein on day 60 (P = 0.650) and rose to 10.04 +/- 1.07 mu mol/g LDL protein (P = 0.001) on day 120. Plasma lycopene dropped from 0.20 mu mol/L on day 2 to 0.02 mu mol/L on day 60 and did not increase by day 120. Carbonyl production rose from 24 +/- 6 mu mol/g LDL protein on day 2 to 42 +/- 4 mu mol/g LDL protein (P = 0.001) on day 60 and dropped to 6 +/- 1 mu mol/g LDL protein (P = 0.001) on day 120, LDL seemed fully protected with 9.7 +/- 2.5 mu mol beta-carotene/g LDL protein, or 2.3 +/- 1.8 mu mol beta-carotene/L plasma.