Researchers affiliated with the Women’s Health Study have concluded that the long-term administration of vitamin E (600 IU of alfa-tocopherol every other day) does not lower the incidence of cancer. The details of this report appeared in the July 6, 2005, issue of the Journal of the American Medical Association .[1]

The potential role of antioxidants in preventing cancer is well recognized in animal models but poorly understood in man. The use of vitamins and various dietary supplementations is an area of preventive medicine that patients often undertake on their own in order to prevent or reduce the risk of disease. One reason many individuals take vitamins is for their antioxidant properties, which, theoretically, should decrease cancer incidence. However, the benefit of supplemental vitamins in preventing cancer has not been determined and could be harmful.

One meta-analysis looked at individuals with chronic diseases who took vitamin E and compared them to those who did not take vitamin E.[2] The doses of vitamin E were considered high, ranging from 16.5 to 2000 International Units (IU) per day (average was approximately 400 IU per day). In sum, there was an increased risk of overall mortality in individuals who supplemented with high-dose vitamin E. The increased risk of mortality was among individuals who ingested vitamin E doses of 150 IU or greater. The researchers concluded that high doses of vitamin E may be associated with an increased risk of mortality. However, it is important to caution that the individuals studied had chronic illness and some individuals were taking vitamin E in combination with other vitamins and minerals.  

A Cochrane report has also concluded that supplementation with antioxidants does not prevent gastrointestinal cancers and, in fact, taking anti-oxidants may actually increase overall mortality.[3] These authors looked at 14 randomized trials that included 170,525 subjects. These trials were designed to determine if one or more antioxidant vitamins decreased the incidence of gastrointestinal cancer or pre-cancer in the case of colon adenomas. These researchers found that the use of antioxidant supplements either alone or in specific combinations did not significantly affect the incidence of esophageal, gastric, colorectal or pancreatic cancers compared to placebo when used for a period of 1-12 years. They also reported that beta carotene with or without vitamin A appeared to increase mortality. In addition, they observed an overall increase in mortality in the antioxidant group, with the magnitude depending of the type of statistic performed. In no analysis was there a decrease in mortality from antioxidant use.

The current Women’s Health Study randomly allocated almost 40,000 healthy women to receive vitamin E every other day or placebo. They found no significant effect of vitamin E on the overall incidence of cancer or specific cancers such as colon or breast. There were no differences in deaths between those taking placebo and those taking vitamin E. These authors concluded that these data did not support vitamin E supplementation in healthy women to prevent cancer or cardiovascular disease.

This randomized trial showed that moderate doses of vitamin E were not effective in decreasing the incidence of cancer in healthy women, but, at least, it did not appear to be harmful. Previous studies have suggested that higher doses of vitamin E can, in fact, be harmful. Thus, there is no current reason for taking vitamin E to prevent cancer.

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