The first study, one of the largest controlled trials of cancer prevention yet conducted, involved 35,500 middle-aged men who took vitamin E, selenium or placebo pills for more than five years. The second trial looked at the effect of vitamins C and E on almost 15,000 male doctors over eight years.

Both studies showed that supplements had no protective effect, either for prostate cancer or for cancer as a whole. Indeed, there were slightly more prostate cancers among men taking vitamin E than in other groups, although the increase was too small to rule out chance as the cause.

In an editorial for the journal, Peter Gann of the University of Illinois, Chicago, said: “Physicians should not recommend selenium or vitamin E – or any other antioxidant supplements – to their patients for preventing prostate cancer.”