http://www.ahrq.gov/clinic/3rduspstf/vitamins/vitaminswh.htm
Agency for Healthcare Research and Quality
The U.S. Preventive Services Task Force (USPSTF) concludes that the evidence is insufficient to recommend for or against the use of supplements of Vitamins A, C, or E, multivitamins with folic acid, and antioxidant combinations for the prevention of cancer or cardiovascular disease.