General chatter - Study suggests antioxidant supplements may not reduce cancer risk




ddc
12-31-2008, 02:59 PM
I rec'd this today in my inbox and thought I'd pass it on:


Study suggests antioxidant supplements may not reduce cancer risk.
The U.K.'s Guardian (12/30, Randerson) reported, "Anti-oxidant supplements do not reduce your risk of developing cancer, according to a trial involving more than 7,500 women," which was conducted by Brigham and Women's Hospital researchers. In fact, "vitamins C, E, beta-carotene, or placebo," whether taken in combination or "on their own...did not" provide notable protection. The finding is a blow to "beloved...health food shops and alternative therapists" that tout "anti-oxidant pills...as preventive therapies to ward off everything from cancer to the signs of aging."

Previous research has shown that those "who eat a healthy diet with lots of fruits and vegetables are less likely to develop cancer, leading to hopes that vitamin supplements containing antioxidants could be of similar benefit," the U.K.'s Telegraph (12/30, Smith) pointed out. Investigators decided to put that theory to the test.

The team "looked at a group of 8,171 women who were randomly assigned to take a supplement, a combination of supplements, or a placebo," HealthDay (12/30, Dotinga) reported. According to the study appearing in the Dec. 30 issue of the Journal of the National Cancer Institute, the "supplements were vitamin C (500 milligrams a day), vitamin E (600 International Units every other day), and beta carotene (50 milligrams every other day)." The participants, aged 40 plus, "took part in the study from 1995 and 1996 until 2005, for an average of nine years," and "they all had cardiovascular disease or were at risk for it."

By trial end, "624 women developed incident invasive cancer (257 breast, 74 lung, 44 colorectal) and 176 women died," MedPage Today (12/30, Grouch) added. Yet, "there was no statistically significant role for any antioxidant on total cancer incidence." Furthermore, "compared with the placebo group, the hazard ratios were 1.11 (95 percent confidence interval 0.95 to 1.30) in the vitamin C group; 0.93 (95 percent CI 0.79 to 1.09) in the vitamin E group; and 1.00 (95 percent CI 0.85 to 1.17) in the beta-carotene group." Likewise, "the antioxidants had no effect on cancer deaths." And, "duration and combined use of the three antioxidants also had no effect on cancer incidence or death, the researchers reported."

Although the results indicate that supplementation does not "offer any measurable preventive effect on cancer in women," Medscape (12/30, Barclay) reported that Demetrius Albanes, M.D., of the National Cancer Institute, pointed out in an accompanying editorial "two specific findings that show the potential of antioxidants for site-specific efficacy." First, "is the possible effect of vitamin E supplementation in preventing colorectal cancer," and "the second is the elevated lung cancer risk in the beta carotene arm, along with modest excess overall cancer risk in smokers and heavier drinkers." Dr. Albanes concluded that "the suggested harmful effects from vitamin C for lung and pancreatic cancers, with the former effect achieving statistical significance, are also noteworthy and raise questions concerning the chemopreventive [potential] of ascorbic acid."