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Long feared for its toxicity, a new study lauds selenium for reducing the risk of some cancers

 
Last Updated: Saturday 04 July 2015

A RECENT study, led by University of Arizona epidemiologist Larry Clark, says that selenium, a mineral found in seafood and liver, helps reduce the risk of certain forms of cancer. The study done on 1,312 patients revealed that when compared with people who took placebos, patients who took daily doses of selenium had 63 per cent fewer cases of prostrate cancer, 58 per cent fewer colon or rectal cancers and 45 per cent fewer lung cancers.

In the selenium group there were 50 per cent less cancer deaths than in the placebo group. But the researchers cautioned that these results needed to be replicated as the study was initially designed to measure only whether selenium would help to prevent skin cancer, Chief sources of selenium which it did not.

Selenium is known to preserve the elasticity of body tissues and is important for the proper functioning of the immune system. While the mineral may prevent cancer by inhibiting turnout growth and inducing 'suicide' in malignant bread cells, Larry Clark said that the mineral might not have been effective in preventing new skin cancers as these malignancies have a mutation in a gene that regulates cell suicide.

Half the patients in the study were given selenium everyday for an average of four and a half years, while the other half got the placebo. The average age of the subjects was 63. Though the selenium dose was triple the recommended daily allowance, it was still within the limits of what the food and drug administration considers 'safe and adequate', said Clark.

People with low levels of selenium in their blood were also shown to be three times as likely to die of1heart attacks as those with higher selenium levels, a finding that may be related to selenium's apparent ability to raise levels of high density lipoproteins, the 'good' cholesterol, which helps protect against heart disease.

Graham A Colditz, an epidemiologist at Boston's Brigham and Women's Hospital called the study "promising but preliminary". "If this possible magic bullet acts through mechanisms suggested by the authors, it is not clear why it should be specific to only some cancers," Colditz said.

In another 15-week study by James Penland, a psychologist at the Human Nutrition Centre of the Agricultural Research Service in North Dakota, US, 15 men who were fed a selenium-rich diet reported a significant improvement in mood, feeling more clear-headed and elated at the end of the study than at the start. A comparable group of men given a selenium-poor diet reported feeling worse.

Most Americans seem to consume enough selenium in their food to satisfy the current recommendation. Surveys have indicated that the average American consumes about 100 microgramme of selenium daily, although in one study in Maryland, 17 per cent of adults took in less than 50 microgramme.

Selenium tends to be richest in foods high in protein. Fish, for example, is an excellent source. The main sources of selenium in the American diet are meats, poultry, fish, cereals and other grains. Among vegetables, mushrooms and asparagus are good sources. Brazil nuts, especially those sold with their shells on, are loaded with selenium two nuts a day can more than meet the daily requirement.

Numerous studies in the '70s suggested that selenium could prevent cancer in animals, but trials on humans have been less conclusive. Selenium is touted by some as a treatment for everything from dandruff to cancer and AIDS.

But, researchers though optimistic, are still very cautious about advising people to start gulping down selenium, as it better absorbed in foods.

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