Dr. Dwyer at USC reported at the March AHA meeting that men who took vitamin C supplements of 500 mg/d or more experienced 2.5 times thickening of their carotid artery walls over 18 months as those men who did not take vitamin C. In smokers, the progression of carotid artery thickening was 5 times greater in those who took vitamin C supplements. Increased carotid artery thickness has been shown to be directly associated with an increased risk of heart attacks and strokes in older adults.1

Claims that vitamin C megadoses lower serum cholesterol and reduce the risk of heart disease was discredited long ago in a study which gave people with high cholesterol levels 4 gm of vitamin C daily for 2 months. This study found no change in total cholesterol or triglyceride levels. However, an unexpected finding was the appearance of an abnormal cholesterol lipoprotein fraction that is associated with a more rapid progression of atherosclerosis in most subjects.2 A study of guinea pigs showed that those who got a normal RDA-type dose of vitamin C lived about 10% longer than those who were given a megadose of vitamin C.3 A recent comprehensive review of the need for vitamin C concluded that ?the totality of the reviewed data suggests that an intake of 90-100 mg of vitamin C/d is required for optimum reduction of chronic disease risk.?4Claims that antioxidant vitamins (Vitamins C & E and beta-carotene) in high doses will prevent chronic degenerative diseases in humans are not warranted. Indeed, high doses of vitamin E may increase the risk of stroke, beta-carotene supplements may increase the risk of some cancers and megadoses of vitamin C may actually increase the risk of heart disease. More research is needed to clearly establish any health risks associated with the use of antioxidant supplements. By contrast, research shows that those who get more of these antioxidants from eating fruits, vegetables and whole grains will greatly reduce their risk of degenerative diseases.By Dr. James J. Kenney, PhD, RD, FACNReferences:1. O?Leary DH et al. N Engl J Med 1999;340:14-222. Peterson VE, Am J Clin Nutr 1975;28:584-73. Davies JEW, Exp Geront 1977;12: 215-64. Carr AC, Am J Clin Nutr 1999;69;1086-107