Here's a look at the study, which was presented yesterday in Washington, D.C., at an international meeting on cancer prevention research hosted by the American Association for Cancer Research (AACR).
The study included some 14,600 male doctors aged 50 and older in the U.S.
Some of the doctors were assigned to take 400 international units (IU) of vitamin E every other day. Others were assigned to take 500 milligrams of vitamin C every day during the study. For comparison, a third group of doctors got placebo pills.
Among all the doctors, there were 1,929 cases of cancer, including 1,013 cases of prostate cancer, during the study. Cancer rates were similar among the doctors taking vitamin E or vitamin C supplements and those taking the placebo.
"After nearly 10 years of supplementation with either vitamin E or vitamin C, we found no evidence supporting the use of either supplement in the prevention of cancer," Howard Sesso, ScD, MPH, says in an AACR news release.
Sesso, who is an assistant professor of medicine at Brigham and Women's Hospital in Boston, adds that there was also no sign that either supplement was harmful.
The findings are only about vitamin E and vitamin C from supplements, not foods.
"Individual vitamin supplements such as vitamin E and C do not appear to provide the same potential advantages as vitamins included as part of a healthy, balanced diet," J. Michael Gaziano, MD, MPH, says in the AACR news release. Gaziano, an associate professor of medicine at Brigham and Women's Hospital, worked with Sesso on the study.
Supplements Industry Responds
The study was "well done" but has some limits, notes Andrew Shao, PhD, vice president for scientific and regulatory affairs at the Council for Responsible Nutrition, a trade group for the supplements industry.
Shao points out that the doctors were "probably very healthy" to begin with, and that the study started when they were already "well along, in terms of age."
The study doesn't settle questions about whether different doses might be more effective, or if starting supplementation earlier in life might make a difference, Shao says.
Beyond that, Shao says lifestyle -- including diet, exercise, and other habits -- seems to matter more than one or two nutrients.
"It really comes down to what is the total package," Shao says. "We can't necessarily expect a couple of nutrients to have a magic bullet effect," especially in a healthy group of people.