Over the years, many laboratory studies have suggested that antioxidants, such as vitamin E, vitamin C, and beta-carotene, may reduce the risk of certain cancers, including prostate cancer . But clinical trials have produced mixed results.

In a study published in the February 15, 2006 Journal of the National Cancer Institute , researchers studied the effect of vitamins E and C and beta-carotene, from both dietary sources and supplements, on the risk of prostate cancer. They found that on the whole, these antioxidants did not reduce the risk of prostate cancer. However, vitamin E supplementation did significantly reduce the risk of advanced prostate cancer in current and recent smokers.

About the Study

The researchers enrolled 29,361 men, aged 55-74 years, who did not have prostate cancer or a history of prostate cancer. All of the participants were screened at the beginning of the study and then annually with a prostate-specific antigen (PSA) test and digital rectal exam (DRE). All study participants filled out a food frequency questionnaire that estimated the amount of vitamin E, vitamin C, and beta-carotene the men were getting through dietary sources and supplements. The researchers divided the men into five groups based on the amount of each antioxidant they took, and then compared the risk of prostate cancer between the groups.

Even after adjusting for age, smoking status, and other relevant factors, supplemental and dietary antioxidant intake did not decrease the risk of prostate cancer. However, a subgroup of current and recent smokers who took more than 400 international units (IU) of vitamin E per day had a significantly reduced risk of advanced prostate cancer compared to current and recent smokers with the lowest vitamin E intake. In addition, men who had low dietary intakes of beta-carotene but took more than 2,000 micrograms (μg) of beta-carotene supplements per day had a reduced risk of prostate cancer compared to men who had low dietary consumption of beta-carotene but did not take beta-carotene supplements.

The average follow-up period for this study was only 4.2 years. Because prostate cancers are often slow-growing, a longer follow-up period is needed to determine whether the associations found in this study hold true over time.

How Does This Affect You?

This study found that for most men, vitamin E, vitamin C, and beta-carotene did not reduce the risk of prostate cancer.

Besides being ineffective, antioxidant supplements may be unsafe. Previous studies have found that high doses of vitamin E may modestly increase the risk of death from heart disease and possibly other causes, and that high doses of beta-carotene may increase smokers’ risk of lung cancer .

A safer option is to get antioxidants from dietary sources. Vitamin E can be found in vegetable oils, nuts, and whole grains; beta-carotene resides in many orange or yellow fruits and vegetables, spinach, and Brussels sprouts; and vitamin C is plentiful in citrus fruits, tomatoes, and broccoli. And, men over 50 years old should talk with their doctors about regular PSA screening for prostate cancer.