Summary
After years of controversy, new study results show clear benefits - decreased mortality, cardiovascular disease, cancer, and stroke - in Finnish men with the highest vitamin E serum levels.
Introduction
Many years ago, male rats fed vitamin E were found to show increased reproductive behavior, and the vitamin became popular in some areas as a sexual enhancement pill for men. It didn't produce any clinically-proven benefits in this direction, however, and interest waned. Then vitamin E became known as an antioxidant, and its use flourished again. People took large doses in the hopes of stemming atherosclerosis, dementia, and cancers.
In 1985 enrollment began in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study in Finland. The study ended in 1993, and in 1996 the investigators reported that beta-carotene supplements were associated with a greater risk of lung cancer in male smokers. This led many investigators to question the benefits of antioxidant supplements, including vitamin E. Although a few vitamin E supplementation trials have shown a reduction in the risk of chronic diseases, a recent analysis of 19 clinical trials suggested a small increase in all-cause death rate with high-dose supplementation.
Follow-up of the ATBC study is now completed, and some interesting results have just been published1. These have been discussed by an editorialist in the same journal, and we summarize his views here.
What's Known About Vitamin E?
Vitamin E is a required nutrient, and comprises 8 structurally related chemicals; the most important one is alpha-tocopherol, a fat-soluble antioxidant. Vitamin E deficiency in man is rare; in affected persons, who have a genetic defect in tocopherol metabolism, the main signs are neurological problems. Serum levels of alpha-tocopherol correlate poorly with dietary vitamin E intake, so that it's difficult to recommend the need for supplementation based on serum levels alone.
There are few signs of toxicity from overdosage, even at doses over 4000 IU. Prolonged prothrombin time, associated with reduced vitamin K levels and a bleeding tendency, is the main side effect at doses above 1600 IU/day. Thyroid hormones are sometimes decreased, and the immunological activity of white blood cells may be reduced.
The Latest ATBC Study Results
The new study report1 correlates outcomes after 19 years' follow-up with serum alpha-tocopherol levels at baseline. The men in the group with the highest serum levels had significantly lower numbers of total (i.e. all-cause) mortality, which included cardiovascular disease and cancer deaths. They also had significantly fewer deaths due to lung or prostate cancer, stroke, and respiratory disease.
These significant reductions in risk were seen as serum alpha-tocopherol levels rose from 9.1 mg/L to about 13 mg/L. The greatest reduction in mortality occurred at levels of 13 to 14 mg/L (30-33 mmol/L).
Making Use of These Findings
As Dr Traber says, "We now have a critical piece of information - that is, serum alpha-tocopherol concentrations of 13 - 14 mg/L optimally reduce mortality due to chronic disease. Now all we have to do is estimate how much alpha-tocopherol to consume to achieve that serum concentration". Easier said than done!
It's been shown that people with normal lipid levels who have a serum alpha-tocopherol level of 8.6 mg/L can increase this to 14.2 mg/L by taking 100 IU vitamin E daily (about 65 mg alpha-tocopherol) as a supplement. However, vitamin E supplements vary - e.g. synthetic or natural - and the amounts of alpha-tocopherol they contain can also vary.
The estimated average requirement for alpha-tocopherol proposed by the Food and Nutrition Board is 12 mg, or 18 IU of vitamin E. This is, in fact, the estimated dietary vitamin E intake in the ATBC study required to yield a serum level of 11.1 to 12.1 mg alpha-tocopherol. However, that study was done in Finnish male smokers. The average dietary consumption of 95% of men and women in the USA is below this level. To increase this intake to 15 mg daily, and thereby achieve relevant increased protection from chronic diseases, would probably require people to take supplements. That is, unless we can come to terms with greater consumption of vitamin E-rich foods: nuts, seeds, and vegetable oils, including olive, sunflower, or safflower oils.
