Selenium for Human Health

In the 1990s there was a great deal of heightened interest generated in a comparatively little known trace mineral named Selenium. Holistic Health Professionals have known for some time that selenium plays a part in the antioxidant enzyme Glutathione Peroxidase, (whence its abbreviation, SeGPX) which is arguably the most important factor in resistance to free radical damage at the cellular level. Therefore, low levels of selenium have been implicated in most chronic disease states, to include cancer, premature aging, cataracts, AMD, cardiovascular disease, osteoarthritis and more.

The research, however, left little doubt as to the extreme importance of paying attention to selenium levels in the diet.

A case in point: in the 1970s, it was discovered that those suffering from a form of juvenile heart disease called Keshan (after a Chinese county), which was characterized in children between 2 and 10 by heart enlargement, heart weakness and irregular rhythm, and fluid on the lungs, had the lowest levels of selenium in their tissues of anywhere in the world!

Supplementing with selenium considerably reduced incidences of the disease, though a possible viral connection meant that not all sufferers responded. This would tie into research done in the 1980s and 1990s, which suggests that viruses become more dangerous where a selenium deficiency exists.

One very important fact about trace minerals is that if they are not present in the soils where foods are grown,
then they will not be present in the food.

 The food crops will grow normally, the animals to whom they are fed will develop normally, but they are not dependent on selenium for health, we are: and we will not be getting it! Interestingly, about 50% of the land mass in the U.S. is either deficient in, or barely at the acceptable level for, selenium. It is therefore obvious that the food chain is going to be a somewhat unreliable source for a steady supply of this important element.

How important?

These recent studies show that selenium supplementation is tied to a dramatic reduction in both the number of cancer cases, and to the number of cancer mortalities, and the study was both significant enough and of a high enough quality to be published in the prestigious Journal of the American Medical Association.

The author of the study, Dr. Larry Clark, became interested in selenium because while doing a study of cancer mortality in North Carolina in the early 1980s, he noticed that there was a pattern of excess mortality from cancer that appeared to follow a geological map of the area. At first, he though this could be explained by pesticide use high in arsenic, or low carotenoid intake, and he was also looking at selenium intake, since selenium is an antagonist of arsenic.

He finally determined that selenium was directly correlated with the cancer data, and that in fact counties where selenium levels in the soil were low, there was a 10% higher mortality from cancer. 



Building on Dr. Clark's research, a recent (1999) study at the University of Colorado began following 1,312 patients with skin cancer.  They were divided into 2 groups, one receiving organic selenium, the other a placebo.  After 4 years, there was no discernible difference in the skin cancer rates, BUT when the researchers looked at other more life-threatening kinds of cancer, they found what Dr. Tim Byers, Professor of Preventive Medicine, called "the most exciting finding we've ever had in nutrition and cancer." The selenium supplemented group had 63% fewer cancers of the prostate, 58% less cancer of the colon, and 46% less lung cancers than the placebo group.  The Selenium used was a high selenium yeast called Selenomax.  

A 2000 study using laboratory rats found selenium from broccoli was highly effective in protecting rats against potent injected carcinogens, with the protection increasing as the doses rose.  You can access this study at

In 2004,

more studies in the Journal of the National Cancer Institute concluded: "The new epidemiologic data on selenium from Li et al. continue to support the initial impressions of this agent's tremendous potential as a prostate cancer preventive agent. The emerging laboratory data greatly strengthen the biologic plausibility for this optimism and for the ongoing randomized clinical selenium trials, which ultimately will be necessary to define the potentially complex risk–benefit profile of this promising preventive agent . Meanwhile, science will continue peeling back layer after layer of the enormously deep and complex onion of selenium effects in the prostate. "

What results can be brought about by optimizing one's levels of selenium?

Dr. Clark's 10 year study showed cancer mortality reduced by 50%, and overall mortality by 17%. Total cancer incidence was reduced by 37%, and three major kinds of cancer were especially affected: lung cancer was reduced by 46%, prostate cancer by 63%, and colon cancer by 38%. (JAMA 1996:276;1957-1963).  Dr. Byers study confirms this result with even better odds!

Selenium and Colon Cancer

Evidence continues to mount that Selenium is intimately connected with rates of colon cancer.  I have one link in Resources to a study suggesting that, and now an analysis of 3 studies comprising more than 1500 patients showed that those with the highest blood levels of selenium had the least risk of recurrence of colon cancer.

The researchers were clear: "higher selenium status may be related to decreased risk of colorectal cancer," write the researchers in the Nov. 17 issue of the Journal of the National Cancer Institute. (

J Natl Cancer Inst 2004;96:1645-1647,1669-1675.)