Selenium is nutritionally essential for humans but is toxic at higher levels, with a narrow safe range of intake. Selenium-containing compounds are known to play an important role in protection against several diseases, including cancer.
That selenium, an essential nutrient, may have a role in carcinogenesis was first suggested nearly 40 years ago. That working hypothesis has subsequently developed support from the results of a large number of animal studies that have consistently found Se supplements to be effective in reducing experimental carcinogenesis in virtually every tumour model investigated.
Cancer is becoming an increasingly significant disease worldwide. Currently, more than 7 million people die each year from cancer. With the existing knowledge, at least one-third of worldwide cancer cases could be prevented.
It was observed that people with higher levels or intake of selenium had lower frequencies of certain types of cancers such as lung cancer, oesophageal and gastric-cardia cancers and, most notably, prostate cancer. The risk of colo-rectal adenoma, a precancerous condition, also seems to be affected.
Newly-published prospective studies on oesophageal, gastric-cardia and lung cancer have reinforced previous evidence, which is particularly strong for prostate cancer. Interventions with Se have shown benefit in reducing the risk of cancer incidence and mortality in all cancers combined, and specifically in liver, prostate, colo-rectal and lung cancers. The effect seems to be strongest in those individuals with the lowest Se status.
In 1977, Gerhard Schrauzer and his team reported that Se is a potential human cancer protective agent. The protective role of Se is supported by numerous epidemiological studies conducted in the USA and elsewhere, as well as in preclinical investigations.
The World Cancer Research Fund found in 2007 that there was probable evidence that selenium and selenium supplements reduced the risk of prostate cancer, and limited suggestive evidence that they reduced the risk of lung and bowel. Selenium was also linked to a limited suggestive lower risk of stomach cancer, and selenium supplements to a limited suggestive increased risk of skin cancer.
Status of selenium in cancer prevention
