USING certain vitamins and supplements does not reduce the risk of cancer, two major studies suggested last night.
Researchers in the United States, studying tens of thousands of patients, found that vitamins E and C, and the mineral selenium, offered no significant protection against cancer.
The results, published in the Journal of the American Medical Associ
ation, appear to contradict the widespread belief that taking vitamins or antioxidant minerals such as selenium can reduce cancer risk.
Although some previous studies have suggested that some of these supplements may have anti-cancer properties, definitive proof has so far been lacking.
In the larger of the studies, more than 35,000 men from the United States, Canada and Puerto Rico were randomly assigned to take either selenium, vitamin E, both selenium and vitamin E, or a placebo.
Although a follow-up period of up to 12 years was originally planned, the study was stopped early by an independent monitoring committee due to the lack of benefit observed. Among the four groups, no statistically significant difference was seen in rates of prostate cancer. In fact, the placebo group had the lowest incidence of cancer.
The other study involved 14,641 male physicians from the US aged 50 or older. Participants received different combinations of vitamin C, vitamin E and a placebo.
During an average follow-up period of eight years, 1,943 cancers were confirmed among the men, including 1,008 cases of prostate cancer.
But neither vitamin reduced the risk of prostate or total cancer by any significant degree. Nor was any significant protective effect seen against specific cancers including bowel, lung, bladder and pancreatic cancers.
The researchers, led by Dr Michael Gaziano, from the Brigham and Women's Hospital and Harvard Medical School, Boston, said: "These data provide no support for the use of these supplements in the prevention of cancer in middle-aged and older men."
In an editorial in the journal, Dr Peter Gann, of the University of Illinois in Chicago, described the findings as "disappointing news".
Both studies had been launched on a "wave of hope" after earlier research hinted that vitamin E or selenium might help prevent cancer, he said.
Dr Jodie Moffat, health information officer at Cancer Research UK, said: "There are a lot of studies looking at whether vitamin and mineral supplements can reduce the risk of cancer but many of them, like this one, don't support a link.
"This new research means it is even less likely than we previously thought that supplements can protect against prostate cancer."
