Vitamin E supplements may do more harm than good, and could contribute to some deaths in higher doses, a new review suggests.
Many people take high doses of the vitamin in the hopes of having it counter the effects of free radicals, molecules that are thought to damage cells and lead to illnesses such as heart disease or cancer.
A recent Johns Hopkins School of Public Health study indicates that high doses of the antioxidant vitamin E (in excess of 400 IU) is linked to an increased rate of mortality.
By reevaluating the data from 19 vitamin E studies over the past decade, the author of the study, Dr. Edgar R. Miller and his research team found that a high daily dose was linked to a six percent increased risk of death.
This finding was presented on Nov. 10 at the American Heart Association's scientific sessions in New Orleans. The study will be simultaneously published in the Nov. 10 issue of the Annals of Internal Medicine.
In their study, the scientists state that the cause of increased risk for death will indeed require further investigation.
However, it is proposed that high doses of vitamin E disrupt the natural balance of antioxidants in the body and increase vulnerability to oxidative damage.
Previous findings indicated that vitamin E may have a protective function by preventing damage to the DNA of cells caused by free radicals.
Another possibility is that the vitamin's anticoagulant properties disrupt proper clotting so much that a person could be at higher risk for a type of stroke known as an intracerebral hemorrhage.
The authors wrote that "any high-dosage vitamin supplements should be discouraged until evidence of efficacy is documented from appropriately designed clinical trials."
Miller and his fellow researchers used a process known as meta-analysis to reanalyze the results from 19 trials which involved 135, 967 subjects. This process combines results from multiple studies that are separate, but related.
Information was simply organized according to whether the patients took high or low doses of vitamin E.
Out of the 19 trials, nine tested vitamin E alone while 10 tested it in combination with other vitamins.
In 11 trials participants took a daily dose of 400 IUs or more of the vitamin.
Findings showed that in nine of these trials there was a six percent increase in death rate among the subjects compared to those who only took placebos.
Low daily doses of vitamin E (approximately 200 IUs daily or less) were administered in the other eight trials. In these eight trials, a clear link with death rate was not established.
The investigators said, however, that the study examined relatively small pools of patients. Most trials included patients who were over the age of 60 and had chronic diseases.
Thus, the findings may have limited relevance for younger, healthy adults and could change if a larger trial size or group with different characteristics were used.
The typical American gets approximately 10 IUs of vitamin E in their diet, while the government recommends 22 IUs.
The scientists note that establishing a daily recommended dose for the antioxidant vitamins (vitamin E, vitamin C, and beta carotene) is difficult, since these antioxidant vitamins react chemically with the free radicals in the body.
In addition, while vitamin C is water-soluble and any excess leaves the body via urine, beta carotene and vitamin E are both fat-soluble so any excess accumulates in the fat cell membranes over time.
There is no recommended dose for vitamin E, although current guidelines set a tolerable limit of up to 1,500 IUs per day.
Doctors say the findings should finally resolve years of conflicting information about high doses of the popular supplement, which is taken to prevent a variety of illnesses, including heart disease, cancer, Alzheimer's disease and recently to counter the effects of aging due to the free radicals.
