Selenium supplements not effective in lowering cancer risk
There is not enough evidence to support the suggestion that taking selenium supplements is an effective way for healthy people to protect themselves against cancer, a systematic review of 55 scientific studies has concluded.
According to the review, which was conducted by a team of researchers from across Europe, people with higher selenium levels were less likely to suffer from certain cancers including bladder and prostate, although no difference was seen in other types, such as breast.
However, the studies - together including more than one million participants could not show whether selenium intake was the reason behind the lower cancer rates in these men and women.
The trace element is crucial to human health, but it may actually be harmful when taken in large quantities.
The team raised the possibility that other factors, including a healthier diet or lifestyle, could have played a larger role than selenium in affecting cancer levels across the study group. This led them to the conclusion that people who are adequately nourished will not benefit from taking these supplements when it comes to cancer risk.
Writing in the latest issue of The Cochrane Library, Dr Gabriele Dennert, from the Institute for Transdisciplinary Health Research in Berlin, Germany, and colleagues explained: They might have had a healthier nutritional intake or lifestyle, have had a more favourable job or overall living conditions.
The systematic review included six randomised controlled trials, all of which were designed to assess whether selenium supplements can help prevent cancer. Those with the most reliable results, as rated by the team, suggested that supplements containing organic selenium did not prevent prostate cancer in men and actually heightened the risk of non-melanoma skin cancer in both men and women.
Some of the trials found that using selenium salt or organic selenium supplements lowered the chances of liver cancer, but the researchers felt that the evidence was less convincing because of limitations in the methodology.
We advise further investigation of selenium for liver cancer prevention before translating results into public health recommendations, they concluded.
We also recommend that there should be further evaluation of the effects of selenium supplements in populations according to their nutritional status as they may differ between undernourished and adequately nourished groups of people.
Yinka Ebo, senior health information officer at Cancer Research UK, said: We know from many large studies that vitamin and mineral supplements far from being potent cancer-fighters are mostly ineffective in protecting against cancer, and can even increase the risk of cancer in some cases. This review on selenium adds to this body of evidence and should give people good reason to think twice before relying on selenium supplements.
The best way to get your full range of vitamins and minerals is to eat a healthy, balanced diet with a wide variety of fruit and vegetables, and this can help protect against cancer. For most healthy people there should be no need to take supplements. Some people are advised to take supplements under medical guidance and should talk to their doctor if they are worried.