Antioxidant vitamins and risk of cardiovascular disease. Review of large-scale randomised trials.
People who consume a diet rich in fruit and vegetables have lower risks of cancer, cardiovascular disease and all-cause mortality. Many prospective cohort studies have reported inverse associations between dietary intake or blood levels of beta-carotene and risks of cancer. Several large-scale trials were set up to assess whether beta-carotene supplementation might reduce the risk of cancer. Subsequently, evidence emerged from basic research which indicated that oxidative modification of low-density lipoprotein cholesterol increases its atherogenicity. The evidence from basic research, and epidemiological evidence for a possible protective effect of antioxidant vitamins for cardiovascular disease was strongest for vitamin E. More recently, further trials were set up to examine if supplementation with anti-oxidant vitamins might also reduce the risk of cardiovascular disease. This review summarises the available randomised evidence from published trials of beta-carotene supplementation involving 70,000 people from 3 large-scale trials in healthy populations and on vitamin E supplementation involving 29,000 patients at high-risk of cardiovascular disease from 5 large-scale trials. The results of these trials have been disappointing and failed to confirm any protective effect of these vitamins for either cancer or for cardiovascular disease.
Clarke
Robert
R
Clinical Trial Service Unit, Radcliffe Infirmary, Oxford OX2 6HE, UK. robert.clarke@ctsu.ox.ac.uk
Armitage
Jane
J
D000975:Antioxidants / Q000627:therapeutic use*; D001161:Arteriosclerosis / Q000378:metabolism / Q000517:prevention & control; D001205:Ascorbic Acid / Q000627:therapeutic use; D002318:Cardiovascular Diseases / Q000378:metabolism / Q000517:prevention & control*; D002338:Carotenoids / Q000627:therapeutic use; D008078:Cholesterol, LDL / Q000378:metabolism; D006801:Humans; D000077276:Lycopene; D018384:Oxidative Stress; D016032:Randomized Controlled Trials as Topic; D018570:Risk Assessment / Q000379:methods; D014810:Vitamin E / Q000627:therapeutic use; D014815:Vitamins / Q000627:therapeutic use*; D019207:beta Carotene / Q000627:therapeutic use
D000975:Antioxidants; D008078:Cholesterol, LDL; D014815:Vitamins; D019207:beta Carotene; D014810:Vitamin E; D002338:Carotenoids; D001205:Ascorbic Acid; D000077276:Lycopene