Antioxidants, but not B-group vitamins increase the resistance of low-density lipoprotein to oxidation: a randomized, factorial design, placebo-controlled trial

We have conducted an intervention trial to assess the effects of antioxidan ts and B-group vitamins on the susceptibility of low-density lipoprotein (L DL) to oxidation. A total of 509 men aged 30-49 from a local workforce were screened for total plasma homocysteine. The 132 selected (homocysteine con centration greater than or equal to 8.34 mu mol/l) men were randomly assign ed, using a factorial design, to one of four groups receiving supplementati on with B group vitamins alone (1 mg folic acid, 7.2 mg pyridoxine, 0.02 mg cyanocobalamin), antioxidant vitamins (150 mg ascorbic acid, 67 mg alpha-t ocopherol, 9 mg beta-carotene), B vitamins with antioxidant vitamins, or pl acebo. Intervention was double-blind. A total of 101 men completed the 8-we ek study. The lag time of LDL isolated ex vivo to oxidation (induced by 2 m u mol/l cupric chloride) was increased in the two groups receiving antioxid ants whether with (6.88 +/- 1.65 min) or without (8.51 +/- 1.77 min) B-vita mins, compared with placebo (-2.03 +/- 1.50) or B-vitamins alone (-3.34 +/- 1.08) (Mean +/- S.E., P < 0.001). Antibodies to malondialdehyde (MDA) modi fied LDL were also measured, but there were no significant changes in titer s of these antibodies in any group of subjects whether receiving antioxidan ts or not. Contrast analysis showed that there was no interaction between a ntioxidants and B-group vitamins. This study indicates that while B-group v itamins lower plasma homocysteine they do not have an antioxidant effect. T hus B-group vitamins and antioxidants appear to have separate, independent effects in reducing cardiovascular risk, (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.