Selenium is used in the CORE™ formula, the foundation of the entire CardioTrim health supplement line.

Selenium is a trace element that is essential in small amounts, but can be toxic in larger amounts. Humans and animals require selenium for the function of a number of selenium-dependent enzymes, also known as selenoproteins. During selenoprotein synthesis, selenocysteine is incorporated into a very specific location in the amino acid sequence in order to form a functional protein. Unlike animals, plants do not appear to require selenium for survival. However, when selenium is present in the soil, plants incorporate it non-specifically into compounds that usually contain sulfur.

Selenium deficiency has been associated with impaired function of the immune system. Moreover, selenium supplementation in individuals who are not overtly selenium deficient appears to stimulate the immune response. In two small studies, healthy and immunosuppressed individuals supplemented with 200 mcg/day of selenium as sodium selenite for 8 weeks showed an enhanced immune cell response to foreign antigens compared with those taking a placebo. A considerable amount of basic research also indicates that selenium plays a role in regulating the expression of cell signaling molecules called cytokines, which orchestrate the immune response.

Geographic studies have consistently shown a trend for populations who live in areas with low soil selenium and have relatively low selenium intakes to have higher cancer mortality rates. Results of epidemiological studies of cancer incidence in groups with less variable selenium intakes have been less consistent, but also show a trend for individuals with lower selenium levels (blood and nails) to have a higher incidence of several different types of cancer. However, this trend is less pronounced in women. For example, a prospective study of more than 60,000 female nurses in the U.S. found no association between toenail selenium levels and total cancer risk. Chronic infection with viral hepatitis B or C significantly increases the risk of liver cancer. In a study of Taiwanese men with chronic viral hepatitis B or C infection, decreased plasma selenium concentrations were associated with an even greater risk of liver cancer. A case-control study within a prospective study of over 9,000 Finnish men and women examined serum selenium levels in 95 individuals subsequently diagnosed with lung cancer and 190 matched controls. Lower serum selenium levels were associated with an increased risk of lung cancer and the association was more pronounced in smokers. In this Finnish population, selenium levels were only about 60% of selenium levels common in generally observed in other western countries. Another case-control study within a prospective study of over 50,000 male health professionals in the U.S. found a significant inverse relationship between toenail selenium content and the risk prostate cancer in 181 men diagnosed with advanced prostate cancer and 181 matched controls. In individuals whose toenail selenium content was consistent with an average intake of 159 mcg/day the risk of advanced prostate cancer was only 35% of that of individuals with toenail selenium content consistent with an intake of 86 mcg/day. Within a prospective study of more than 9,000 Japanese-American men, a case-control study that examined 249 confirmed cases of prostate cancer and 249 matched controls found the risk of developing prostate cancer to be 50% less in men with serum selenium levels in the highest quartile compared those in the lowest quartile, while another case-control study found that men with prediagnostic plasma selenium levels in the lowest quartile were 4 to 5 times more likely to develop prostate cancer than those in the highest quartile. In contrast, one of the largest case-control studies to date found a significant inverse association between toenail selenium and the risk of colon cancer, but no associations between toenail selenium and the risk of breast cancer or prostate cancer.

Theoretically, optimizing selenoenzyme activity could decrease the risk of cardiovascular diseases by decreasing lipid peroxidation and influencing the metabolism of cell signaling molecules known as prostaglandins. However, prospective studies in humans have not demonstrated strong support for the cardioprotective effects of selenium. While one study found a significant increase in illness and death from cardiovascular disease in individuals with serum selenium levels below 45 mcg/liter compared to matched pairs above 45 mcg/liter, another study, using the same cutoff points for serum selenium, found a significant difference only in deaths from stroke. A study of middle aged and elderly Danish men found an increased risk of cardiovascular disease in men with serum selenium levels below 79 mcg/liter, but several other studies found no clear inverse association between selenium nutritional status and cardiovascular disease risk. In a multi-center study in Europe, toenail selenium levels and risk of myocardial infarction (heart attack) were only associated in the center where selenium levels were the lowest.

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