The Potential Health Risks of High-Dose Vitamin E Supplement Use
Recently published studies have suggested that vitamin E supplements not only fail to prevent heart disease and cancer, but may actually harm people who take high doses over a long term. However, these studies are limited by the fact that they involved:
people 55 years or older who already had heart disease or diabetes;
people with cancer or who previously had cancer; and
people who may be at higher risk of developing these diseases.
One study found that patients with heart disease or diabetes who took 400 IU of vitamin E daily for an average of seven years were at a significantly increased risk of heart failure compared to patients who were not taking vitamin E supplements. This study concluded that high-dose vitamin E supplements (400 IU or greater) should not be taken by patients with heart disease or diabetes.
In another study, daily doses of 400 IU of vitamin E were given to patients receiving radiation therapy for cancers of the head and neck. The theory was that the antioxidant treatment might reduce the incidence of additional cancers of the same type among these patients. However, it was found that those who received vitamin E supplements were significantly more likely to develop other similar cancers during the supplementation period than those receiving a placebo.