DOCTOR'S VIEW ARCHIVE
Vitamin E May Cut The Risk Of Prostate Cancer
PARIS-Vitamin E lowered the incidence of prostate cancer by a third in a large study of smokers in Finland but beta carotene, a form of vitamin A, did not give similar benefit.
Prostate cancer is the most frequently diagnosed cancer in U.S. males. It is estimated that there will be more than 180,000 cases in 1998 along with close to 40,000 deaths. African-American men have the highest rates of prostate cancer in the U.S.
Both vitamin E and beta carotene are anti-oxidants, compounds thought to prevent carcinogens (cancer-causing agents) from damaging the DNA and so setting the stage for cancer.
In the Finnish study, vitamin E was tested in the form of alpha tocopherol. It appeared to protect also against colorectal and lung cancer, but the protection was nowhere as great as against prostate cancer.
The trial, dubbed the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study (ATBC Study), was carried out by the U.S. National Cancer Institute and the National Public Health Institute of Finland. The report by O.P. Heinonen and colleagues appeared in the March 18, 1998, issue of the Journal of the National Cancer Institute.
The ATBC study included some 29 thousand males, all smokers, age 50 to 69. The men were divided into four groups of equal size. One group took beta carotene. Another took vitamin E. Still another took both beta carotene and vitamin E. And the last group merely took a placebo (an inactive pill that looked like these vitamins).
Women were not included in the ATBC study because their rate of lung cancer was much lower than the rate for Finnish men. (In 1985, the annual age-adjusted lung cancer rate was 67 cases per 100,000 men compared to 8 cases per 100,000 women in Finland).
The men taking vitamin E (alone or with beta carotene) had 32% fewer cases of prostate cancer after 5-8 years. And there were 41% fewer deaths from prostate cancer in men on vitamin E, suggesting it may impede the progression of a prostate tumor to a more malignant state. (Many older men have tiny microscopic areas of cancer in the prostate but fortunately most do not progress to life-threatening disease).
The vitamin E dosage used in the ATBC study was 50 milligrams a day, the equivalent of 50 international units (i.u.). (Multivitamins generally contain about 30 i.u. of vitamin E while single supplements most often have a minimum of 100 i.u of vitamin E). The dose of 50 i.u. in the Finnish study is about five times the Recommended Dietary Allowance. of vitamin E for men and about three times what most people get from food.
Foods rich in vitamin E include vegetable oils (particularly those from safflower, sunflower and cotton seeds), grains, and nuts. The leading sources of vitamin E in the U.S. diet include salad dressings and mayonnaise, margarine, cake, cookies, donuts, and eggs. To ingest 50 international units of vitamin E from such foods would mean also taking in a great deal of extra fat, not necessarily a good idea.
Vitamin E supplements may also not be free of risk. Among those taking it in the study, there were 66 deaths from the cerebral hemorrhage compared with 44 such deaths among the men not taking vitamin E.
Finland was selected as the site for the ATBC study because it has a high lung cancer rate in men (thought to be due mainly to cigarette smoking), it has a clinic system for screening and treating lung diseases (through which smokers could participate in the study) and it has a national cancer registry to track all known cases of cancer (important in such a large trial).
The National Cancer Institute provided about $20 million over 10 years for the trial, with a similar sum contributed by Finland. The pharmaceutical firm Hoffmann-LaRoche supplied the 60 million pills the men took during the trial.
Since a large dose of vitamin E provided significant protection against prostate cancer in this study, should everyone (or all men at least) start taking vitamin E supplements? The answer is "no."
Just as Finland has features helpful to undertake such a study, it also has certain limitations. The overall population in Finland is much more uniform with far less ethnic and racial diversity than in many other countries such as the U.S. Other populations therefore clearly need to be tested. Finland aside, a result of this importance requires confirmation.
It is clearly premature to recommend vitamin E supplementation for prostate cancer prevention. Nevertheless, we do recommend that readers stay alerted for further information in this area.
Last Editorial Review: 7/22/1998
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