October 13, 2011
Study: Vitamin E Increases Prostate Cancer Risk
(Ivanhoe Newswire) — Guys, before you take that daily supplement, read this! According to a new study, men who were randomized to receive daily supplementation with vitamin E had a significantly increased risk of prostate cancer.
Lifetime risk of prostate cancer in the United States is currently estimated to be 16 percent. Although most cases are found at an early, curable stage, treatment is costly and urinary, sexual, and bowel-related adverse effects are common.
The long-term effect of vitamin E and selenium on risk of prostate cancer in relatively healthy men has been studied by the Cleveland Clinic. The study included a total of 35,533 men from 427 study sites in the United States, Canada, and Puerto Rico who were randomized between August 2001 and June 2004. Eligibility criteria included a prostate-specific antigen (PSA) measure below a certain level, a digital rectal examination not suspicious for prostate cancer, and age 50 years or older for black men and 55 years or older for other men. The primary analysis included 34,887 men who were randomly assigned to 1 of 4 treatment groups: 8,752 to receive selenium (200 micrograms/day); 8,737, vitamin E (400 IU/day); 8,702, both agents; and 8,696, placebo, with a planned follow-up of a minimum of 7 years and maximum of 12 years. Analyses reflect the final data collected by the study sites on their participants through July 5, 2011.
Since the initial report, a total of 521 additional prostate cancers have been diagnosed: 113 in the placebo group, 147 in the vitamin E group, 143 in the selenium group, and 118 in the combination group. The researchers found that the rate of prostate cancer detection was greater in all treatment groups when compared with placebo but was statistically significant only in the vitamin E alone group (a 17 percent increased rate of prostate cancer detection). Compared with the placebo group, in which 529 men developed prostate cancer, 620 men in the vitamin E group developed prostate cancer, as did 575 in the selenium group and 555 in the selenium plus vitamin E group. The difference in rates of prostate cancer between vitamin E and placebo became apparent during the participants' third year in the trial. The elevated risk estimate for vitamin E was consistent across both low- and high-grade disease.
"The observed 17 percent increase in prostate cancer incidence demonstrates the potential for seemingly innocuous yet biologically active substances such as vitamins to cause harm. The lack of benefit from dietary supplementation with vitamin E or other agents with respect to preventing common health conditions and cancers or improving overall survival, and their potential harm, underscore the need for consumers to be skeptical of health claims for unregulated over-the-counter products in the absence of strong evidence of benefit demonstrated in clinical trials," Eric A. Klein, M.D., of the Cleveland Clinic was quoted saying.
SOURCE: JAMA, October 12, 2011