Prevention of age-related macular degeneration:
A randomized controlled trial studied the long-term use of vitamin E for preventing macular degeneration. For four years, 1193 healthy volunteers aged 55-80 took either 500 IU of vitamin E or a placebo pill daily. At the end of the study, people taking vitamin E developed age-related macular degeneration at about the same rate as people taking the placebo (8.6% versus 8.1%). These results indicate that daily supplementation with vitamin E does not prevent the development of macular degeneration, but this study does not address whether it has any effects greater than four years down the line.
In a very large clinical trial, patients with high-risk heart disease were randomly split into two groups: 4761 took 400 IU of vitamin E, while 4780 took a placebo pill. It was found that the patients in both groups had similar rates of heart attacks, strokes, death from coronary heart disease, and death from any cause. This indicates that supplementation with 400 IU of natural vitamin E does not reduce the risk of cardiovascular events in high-risk patients.
A separate analysis of seven large trials covering 81,788 subjects revealed that vitamin E did not lower the death rate or significantly decrease the risk of death from heart disease.
- In a randomized controlled trial, 341 patients with Alzheimer's disease were randomly assigned to one of four groups: (1) selegiline (an MAOI) alone, (2) 2000 IU of vitamin E alone, (3) both selegiline and vitamin E, or (4) two placebo pills. Patients taking vitamin E alone had a higher average time to progression of Alzheimer's disease than all other groups.
- In a prospective cohort study, 815 healthy adults older than age 65 were asked about their diets and followed to see whether their dietary intake of antioxidants would affect the risk of developing Alzheimer's disease. After about four years, it was found that the people who developed Alzheimer's disease, on average, consumed less vitamin E in their diet (not from supplements) than people who did not develop the disease. However, because this study only followed people for four years, it did not address the long-term effects of dietary antioxidants. Also, a problem with nutrition studies is that they measure dietary intake of foods with a questionnaire at the time of the study, and have no way of assessing what a person's diet was like throughout his or her life.
- A similar prospective cohort study followed 5393 men and women at least 55 years old for an average of six years. It was found that, after adjusting for many variables that affect the development of Alzheimer's disease, high intake of vitamin C and vitamin E were correlated with lower risk of this disease. However, one problem with this study is that people who were starting to develop Alzheimer's disease at the start of the study, but were not yet diagnosed, may have had a poorer diet (lower intake of antioxidants) or may have had a hard time filling out the diet questionnaire, and this may also explain the association.
Prevention of prostate cancer:
Initial data from a large scale Selenium and Vitamin E Cancer Prevention trial (SELECT) shows vitamin E taken alone or with selenium for five years, did not reduce the risk of prostate cancer. A small increase in prostate cancer cases was observed in men taking only vitamin E.
Prevention of prostate and lung cancer in male smokers:
A randomized controlled trial studied the effects of beta-carotene and vitamin E supplements on the risk of prostate cancer. A total of 29,133 male smokers (50-69 years old) were split into four groups: (1) 50 mg of vitamin E, (2) 10 mg of beta-carotene, (3) both supplements, or (4) two placebo pills. Compared to the placebo group, the men taking vitamin E had an average of 36% lower risk of prostate cancer. However, men taking beta-carotene had an increased risk of lung cancer, heart disease, and hemorrhagic stroke. These results may not apply to women.
A recent review of 14 clinical trials shows that supplementation with antioxidants beta-carotene, vitamins A, C, and E does not seem to prevent gastrointestinal cancer and may actually increase overall mortality.
Head and neck cancer:
This study involved 540 patients with head and neck cancers who were given either 400 IU/day of vitamin E or placebo starting on the first day of radiation therapy for three years. Researchers found that patients who received vitamin E had a higher rate of second primary cancer compared to those on placebo. They also suggest that vitamin E may interfere with radiation therapy.
A randomized controlled trial studied the effects of vitamin E and selegiline (an MAOI) on the progression of Parkinson's disease. Eight hundred patients with Parkinson's disease were randomly assigned to one of four groups: (1) 2000 IU vitamin E, (2) 10 mg of selegiline, (3) both medications, or (4) two placebo pills. At the end of the study, it was found that patients taking vitamin E progressed just as rapidly as patients who were taking a placebo pill. This indicates that vitamin E is not effective for this use.
In a placebo-controlled, randomized trial involving 120 patients, 800 IU daily of vitamin E has been shown to be more effective than a placebo in reducing hot flashes in breast cancer survivors. However, most patients did not prefer vitamin E over the placebo at the conclusion of the study. The author pointed out the clinical magnitude of the reduction was marginal.