Most people know the importance of keeping minerals such as sodium, potassium and calcium at adequate (or optimal) levels in order to maintain health, but a very often over looked mineral has been shown to possess a multitude of disease and age fighting benefits. This mineral, which we did not learn about in those Life Education vans (yay air conditioning!) is selenium! Discovered to be essential when laboratory rats developed liver disease from being fed the selenium-deficient torula yeast instead of the usual baker's yeast, it functions as a regulator of many metabolic and physiological pathways.
One of the benefits of selenium is of course increasing longevity. For example, a study of 446 people in China, 208 of which were centenarians (those 100 years old or over), found that the highest levels of selenium and zinc were in the oldest participants. In a nine-year study of older adults in France, those with the highest blood levels of selenium had lower death rates. Compared to those with the highest selenium levels, people with the lowest levels had a 54% higher risk of dying during the study period, and a 79% higher risk of dying from cancer.
Yes, selenium has been shown in many studies to help protect against cancer. Nine randomised controlled trials involving over 152,000 people in total show that selenium supplementation reduced the risk for all cancers by an average of 24%; this rose to 36% in people with low starting levels of selenium. More specific studies have found protective effects against prostate, colorectal, liver, stomach, bladder, oesophagus and lung cancers. However, there are three specific forms of selenium that are most effective in cancer prevention; which are sodium selenite, L-selenomethionine and selenium-methyl L-selenocysteine. These each have their own mechanisms of action, and so each is better at fighting certain cancers than others. The first boosts the natural immune response against cancer cells, killing them off before they develop into noticeable issues. The second makes cancer cells kill themselves in the very early stages, before they lose the "suicide genes", while the third can kill abnormal cells that have lost those genes.
Have there been human clinical trials to back these up? Yes! In one of these, patients with head and neck cancers took either 200ug of sodium selenite or placebo, with the treated patients showing a better ability to destroy tumour cells. In another, patients with precancerous damage to the oesophagus were prescribed 200ug of L-selenomethionine. This not only slowed progression of some abnormal cells, but also caused the regression of precancerous cells back to normal states! Clinical trials have even shown risk reductions in BRCA gene-related breast cancers. Strikingly, L-selenomethionine was found to lower prostate cancer risk by 63% in men with a history of this disease.
Selenium can also increase efficacy of immune cells to fight infections, thus reversing age-related immune decline. One example of its immune-boosting properties is a study of people with type one diabetes, where the hepatitis B vaccine was 74% effective with 200ug of selenium, as opposed to 48% in the placebo group. With these benefits, as well as protective effects against cognitive decline, stroke-induced brain damage and cardiovascular disease, it is surprising that selenium is so overlooked. The main mechanism behind these, by the way, is the requirement of selenium for glutathione to function as an antioxidant.
Derived from "How To Obtain Optimal Benefits from Selenium", Life Extension Magazine, November 2015.