Taking the mineral selenium does not protect against cancer, according to an analysis published today.
Researchers carrying out a Cochrane Systematic Review of 49 observational studies on selenium intake, and six randomised controlled trials on the effects of selenium supplements.
They state that, although a number of health conditions have been linked to selenium deficiency, selenium is toxic in large doses.
Results from the observational studies indicate that people, especially men, with a higher selenium intake "may be marginally protected from cancer" including non-melanoma skin cancer or prostate cancer. But the benefit is not seen in the more rigorous randomised controlled trials.
Lead researcher, Dr Gabriele Dennert of the Institute for Transdisciplinary Health Research, Berlin, Germany, said: "In fact, the results of the Nutritional Prevention of Cancer Trial and the Selenium and Vitamin E Cancer Prevention Trial raised concerns about possible harmful effects from long-term use of selenium supplements."
He added that: "These conclusions have limitations because the data came from a wide variety of trials, and so it is difficult to summarise their findings." But in conclusion, he says: "We could find no evidence to recommend regular intake of selenium supplements for cancer prevention in people whether or not they already have enough selenium."
The team adds that more research is needed on the effects of selenium on liver cancer, as well as possible gender differences on the impact of selenium intake.
A previous Cochrane systematic review in 2010 also concluded that there was no convincing evidence that selenium supplements could prevent cancer in men, women or children.
Dennert, G. et al. Selenium for preventing cancer. Cochrane Database of Systematic Reviews 2011, Issue 5. Art. No.: CD005195.
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