Selenium and reduced risk of cancer

The results of Dr. Larry Clark’s Nutritional Prevention of Cancer trial showed the efficacy of selenium supplementation in reducing the risk of colon cancer, lung cancer, and prostate cancer. Now, a meta-analysis of 69 studies shows that higher selenium exposure is associated with reductions in the risk of breast cancer, lung cancer, and prostate cancer.

Authors of a recent meta-analysis of 69 studies of selenium exposure and cancer risk have concluded that high selenium exposure can reduce cancer risk, especially high selenium exposure that is reflected in high plasma or serum selenium status and/or in high toenail concentrations [Cai 2016].  Admittedly, higher selenium intakes (as compared to lower selenium intakes) can affect different forms of cancer differently.  We still need more research to sort out which forms and dosages of dietary and supplemental selenium are most effective at reducing cancer risk.  In this article, I want to summarize the findings of Dr. Xianlei Cai and colleagues.

What is a meta-analysis of selenium exposure and cancer risk?
A meta-analysis is a research method of combining the data from several selected research studies to reach conclusions that have greater statistical power.  In the present case, Cai et al selected 69 studies that met their inclusion criteria.  Each one of the 69 selected studies had the following characteristics:

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Selenium and heart disease

A study of serum selenium levels and supplementation with a patented organic selenium yeast preparation shows an association between serum selenium concentrations and the rate of deaths from heart disease in healthy elderly study participants.

There have been two noteworthy discoveries from a recent randomized controlled trial conducted by Dr. Urban Alehagen of Linköping University (Sweden) and his colleagues.

Firstly, people with low concentrations of selenium in their blood were found to be at significantly higher risk of death from heart disease.

Secondly, a combination of a patented high selenium yeast supplement and a proven Coenzyme Q10 supplement taken daily for four years provided significant protection against heart disease in people with low serum selenium status.

The KiSel-10 study of cardiovascular mortality
The study enrolled 668 healthy elderly individuals aged 70-80 years.  The study was well-designed and well-executed.  One group of 219 randomly selected individuals received 200 micrograms of selenized yeast tablets and 200 milligrams of Coenzyme Q10 capsules daily for four years. A second randomly assigned group of 222 individuals received matching placebos.  The remaining group of 227 individuals received no treatment at all.

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Selenium and heart muscle tissue

Daily nutritional supplementation with a combination of organic high-selenium yeast and Coenzyme Q10 for four years slowed the decline of heart function that is frequently associated with ageing.

The heart muscle tissue is frequently the first tissue in humans to suffer damage caused by selenium deficiency.  When the cell membranes in the heart muscle tissue are damaged by the action of harmful free radicals (this is called oxidative damage), many of the healthy heart muscle cells are replaced by fibrous tissue.  The resulting condition is called cardiomyopathy.

Cardiomyopathy is a disease of the heart muscle in which the heart is enlarged, thick, and rigid [Mayo Clinic].  As the cardiomyopathy worsens, the weakened heart muscle is less and less able to pump adequate quantities of blood to carry oxygen and nutrients to the cells and tissues throughout the body.  Eventually, symptoms such as shortness of breath, early fatigue, and swelling in the legs and feet and abdomen appear, the symptoms of chronic heart failure.

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