Vitamin E, also known as tocopherol, was long believed to be a potent antioxidant that protects cell membranes and other fat-soluble parts of the body, such as low-density lipoprotein (LDL) cholesterol from damage. It was also believed to protect the body against cardiovascular disease and certain forms of cancer and has demonstrated immune-enhancing effects.

Initially, vitamin E was thought to be a potentially beneficial nutrient in lowering the risk of prostate cancer or of tapering its growth. However, research today paints a different picture.

More than 29,000 men were initially included in a study which intends to find association between dietary or supplemental vitamin E intake and prostate risk, National Cancer Institute reports.

Buoyed by the promising results of the study, a large randomized clinical trial, called SELECT (Selenium and Vitamin E Cancer Prevention Trial) began in 2001. The study was intended to determine whether a 7 to 12 year daily supplementation with synthetic vitamin E (400 IU), with or without selenium (200 mcg), reduced the number of new prostate cancers in more than 35,000 healthy men age 50 and older.

The trial was halted in October 2008 when an analysis found that the supplements, taken alone or together for about 5.5 years, did not prevent incidence prostate cancer.

The updated 2011 SELECT data published recently included 18 months of additional follow-up information on participants through July 5, 2011. At that time, participants of the SELECT research, were no longer taking the supplements. Data culled from almost seven years of information on the participants included 5.5 years of taking the supplement and 1.5 years of observation or follow-up.

Additional data yielded a compelling issue. The research showed that men who took vitamin E had a seventeen percent (17%) relative increase in the number of men with prostate cancer compared to those who were given placebo.

The difference in the incidence of prostate cancer between those men who were taking vitamin E only and those on placebo turned out to be statistically significant and not likely to be attributed to chance.

Though comparatively smaller in terms of increase and not statistically significant, men who were taking selenium alone, or combination of vitamin E and selenium, were more like to develop prostate cancer that those on placebo.

The findings of the study published in the Journal of the American Medical Association points to the importance that consumers should be wary of health claims for unregulated over-the-counter products in the absence of sound evidence of benefit manifested in clinical trials.