Saturday April 19, 2014 (foodconsumer.org) -- A new study published recently in Journal of the National Cancer Institute suggests that high intake of supplemental selenium and vitamin E may increase risk of prostate cancer depending upon the selenium status.

An early study found high intake of supplemental vitamin E was associated with 17% increased risk of prostate cancer.   The current study led by Alan R Kristal, DrPH from Fred Hutchinson Cancer Research Center in Seattle, Washington found that the effect of vitamin E supplements on the risk of prostate cancer has something to do with the status of selenium.

Both selenium and vitamin E are known antioxidants and considered preventive against carcinogenesis induced by harmful free radicals generated by a chemical process called oxidation.

The current case-control study involved 1739 total and 489 high grade (Gleason 7-10) prostate cancer cases and 3117 men as controls.  Baseline toenail selenium indicating the status of selenium in a man was determined.

Analyses based on Cox proportional hazards models  show toenail selenium was not correlated with prostate cancer when selenium supplements were not used.  

Selenium supplementation (including both selenium only and selenium plus vitamin E types of supplementation) was not associated with prostate cancer among men with low selenium status.

However, among men with high selenium status, the risk of high prostate cancer was increased by 91% when they used selenium supplements with or without vitamin E included.

Vitamin E only supplementation did not increase risk of prostate cancer of any type among men with high selenium status, but increased the risk of total, low grade and high grade prostate cancer by 63%, 46% and 111% respectively, among those with low selenium status.

In short, too much selenium may increase risk of prostate cancer in men with high selenium status and too much vitamin E may increase the risk in men with low selenium status.

The researchers suggested "Men should avoid selenium or vitamin E supplementation at doses that exceed recommended dietary intakes."

It should be noted that the study is not a trial, that is, the results of the study could not prove that supplementation of vitamin E and selenium is definitely a risk factor for prostate cancer although the possibility could not be excluded either.

In any case, high doses of selenium and vitamin E do not seem to be necessary as no evidence indicates that either supplement in high doses may be used as a therapy or preventative for the treatment and prevention of prostate cancer.

Selenium is found high in Brazil nuts, sunflower seeds, mushrooms, grains and onions.  And vitamin E is found high in foods like sunflower seeds, spinach, Swiss chard, almonds, avocado and peanuts.  It is safe to eat selenium and or vitamin E rich foods. (David Liu)