How much selenium every day?

Yes, good health depends on good genes. But it also depends on good diet, good exercise, good sleep, and adequate intakes of essential bio-nutrients such as selenium and Coenzyme Q10.

The proper daily dosage of selenium for normal people?   Normal people?  How many of us are approximately normal?  68 percent of us, perhaps?  Yes, we humans are more the same in many ways than we are different.  However, there is considerable biochemical variation amongst us humans.  So, it is difficult to say who is average and normal and then suggest an ideal daily dosage of selenium.

What do the numbers from selenium studies say?
Let’s look at the numbers from published research and see what sense we can make of them.  Remember: we humans need adequate plasma selenium concentrations for optimal antioxidant and anti-viral and anti-carcinogenic protection [Schrauzer 2009].

Putative beneficial range for plasma selenium status
Hurst and Fairweather-Tait et al, researchers based at Norwich Medical School, University of East Anglia, in the United Kingdom have suggested that the “putative beneficial range” lies between 120 and 150 nanograms of selenium per milliliter of plasma [Hurst 2010].

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Selenium and the prostate

Next to skin cancer, prostate cancer is the most common cancer in men in the United States. It is a leading causes of cancer death among men of all races and ethnic backgrounds. Low selenium status is associated with increased risk of prostate cancer.

There have been some recent research results relating to selenium supplementation and prostate gland tissue.  Researchers in The Netherlands have published results showing that a five-week daily intervention with a high-selenium yeast supplement, 300 micrograms daily, is associated with a down-regulation of genes that are involved with cellular growth and proliferation, with cellular immune response, and with inflammation processes.  Also down-regulated by the selenium supplementation is the activity of genes involved with wound-healing [Kok 2017].

The Dutch study was a randomized, double-blinded, placebo-controlled study.  Interestingly, the researchers saw the opposite effect in the placebo group.  In the placebo group, there was an up-regulation of the genes involved in cellular immune response [Kok 2017].

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Prostate cancer risk and selenium status

Selenium supplements in the form of organic high-selenium yeast tablets provide the best cancer chemo-protection. These supplements are made using the yeast species Saccharomyces cerevisiae in a selenium-enriched growth medium. The yeast cells that produce the high selenium yeast tablets are rendered inactive. They are killed off by a heating process. Strains of the same yeast species are used to brew beer and bake bread.

Selenium supplementation and the risk of prostate cancer?  What do we know?  We need to be careful in interpreting the research results that we have (and we need more research), but, yes, there is evidence for an inverse association between prostate cancer risk and selenium status [Hurst 2012].

As of this writing (April 2017), the protective effect of selenium supplementation against prostate cancer seems to be found in a relatively narrow range of plasma selenium status [Hurst 2012].  Furthermore, there seems to be a U-shaped relationship between selenium status and protection against prostate cancer.

If the concentrations of selenium in the plasma are too low, there is increased risk of prostate cancer.  This is a serious concern in many regions of the world.

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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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Daily intakes of selenium

Dietary intakes of selenium vary considerably from person to person and region to region. Selenium supplements are necessary to raise selenium status sufficiently to prevent oxidative damage to the cells, to improve immune function, and to reduce the risk of cancer and heart disease.

How much selenium from food and supplements do we need on a daily basis?  Which bio-markers of optimal selenium status seem to be most useful to answer this question?  Dr. Rachel Hurst and Dr. Susan J. Fairweather-Tait, Norwich Medical School, United Kingdom, and their colleagues set out to find answers.    The design of their study is very interesting.

They enrolled 119 healthy British men and women aged 50 – 64 years in a randomized, double-blind, placebo-controlled study that lasted 12 weeks [Hurst]. They excluded the following persons from the study:

  • smokers
  • overweight people
  • people with already high plasma selenium status
  • people with long-term illnesses
  • people on various medications
  • people unwilling to discontinue taking vitamins and herbal remedies at least one month prior to the start of the study

The 119 study participants received either placebo or one of the following treatments:

  • selenium-enriched yeast tablets containing 50, 100, or 200 micrograms of a patented organic selenium (SelenoPrecise® preparation delivered by Pharma Nord, Denmark)
  • selenium-enriched onion meals that provided the equivalent of 50 micrograms of selenium per day
  • unenriched onion meals that provided the equivalent of less than 4 micrograms of selenium per day

Measurements of selenium
Remember:
Selenium is a trace element.  We measure its intake in micrograms per day, not milligrams.  We measure selenium status in plasma and serum in terms of micrograms per liter (or equivalently, in nanograms per milliliter).  Selenium in toenails or hair, then, we measure in micrograms per gram.

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What is a high selenium yeast supplement?

Baker’s yeast and brewer’s yeast and high selenium yeast … all strains of the same species of yeast … Saccharomyces cerevisiae … High selenium yeast preparations are the most effective form of selenium supplements. The yeast in the tablets is dead and inactive. There is no risk of a yeast infection from a high selenium yeast preparation.

The trace element selenium is an essential component of the selenium-dependent enzymes called selenoproteins.  We need these selenoproteins for the optimal biological functioning of our cells.  Specifically, we need adequate daily intakes of selenium for the protection of cellular DNA, for successful reproduction, for proper thyroid gland function, for protection against infections, for anti-oxidative protection against the damage caused by free radicals, and for the prevention of cancer and heart disease.

What form of selenium is best?
Many of us cannot get enough selenium in our diets, especially if we do not regularly eat Brazil nuts (very high in selenium) or if we eat relatively little meat and fish.  However, there are various supplemental forms of selenium available to us as consumers.

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Our bodies cannot make selenium for us

Cancer studies
The research base for supplementation with selenium shows the need for adequate daily selenium intakes and adequate selenium status. The formulation and the dosage of the selenium supplement are very important.

Daily selenium intakes?  We need to get this essential trace element – selenium — in our diets and in our supplements because our bodies cannot make it for us. The work of Dr. Gerhard N. Schrauzer, Dr. Raymond J. Shamberger, and Dr. Douglas V. Frost has shown that there is an inverse relationship between our selenium status and the risk of cancer mortality.  Animal studies show an inverse correlation between selenium status and incidence of cancer.  Observational studies show lower risk of various types of cancer with higher selenium status.

Intervention studies of selenium supplementation and cancer
Clinical studies in China
Large interventional studies in China, a region of the world with selenium-poor soils and foodstuffs, have shown that selenium supplements protect against hepatitis B virus and primary liver cancer [Yu] and that supplementation with a combination of selenium and other antioxidants reduces cancer incidence and mortality in a region characterized by high cancer mortality rates [Blot].

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Selenium and colorectal cancer: The Bonelli study

bonelli study
The Bonelli study showed that a selenium-based antioxidant supplement combination reduces the risk of developing new adenomatous polyps in the large intestine following the removal of colorectal polyps. Adenomas, if not prevented or removed, can develop into colorectal cancer tumors.

Dr. Luigina Bonelli and a team of researchers in Genoa, Italy, were motivated by the following set of compelling facts:

  • Colorectal cancer was the second leading cause of cancer death in Europe.
  • Adenomas in the colon (adenomas are benign tumors, which sometimes transform to malignant tumors) were known to be precursors of colorectal cancer.
  • Patients who had undergone a colonic polypectomy (removal of an adenomatous polyp) had an increased risk of developing colorectal cancer and needed to have periodic follow-up colonoscopies.
  •  Increased risk of developing adenomas was equated with increased risk of developing colorectal cancers.
  •  Observational studies indicated that there was an association between the plasma or serum concentrations of several antioxidant substances including selenium and the risk of colorectal cancer.
  •  In some intervention studies, supplementation with selenium was associated with reductions in the incidence of colorectal cancer.

The time was right to start a large study of the effectiveness of selenium and other antioxidants in reducing the risk of colorectal cancer.

Selenium to reduce the risk of colorectal cancer
Dr. Bonelli and her colleagues wanted to see if daily supplementation with a combination of antioxidants including selenium could reduce the risk of recurrent adenomas in patients who had had one or more adenomatous polyps removed.  The researchers designed a randomized, double-blind, placebo-controlled clinical trial and, over the period of many years, they enrolled a total of 411 patients who had undergone a polypectomy.

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How we know that selenium supplementation is important

Selen supplementation, virus
Adequate intakes of selenium are needed to ensure the optimal functioning of the selenoproteins in the body. Selenoproteins provide protection against the development of cancer and heart disease; they are important for immune system defense; they protect against damage caused by heavy metals and chemical toxins and radiation. And, there is evidence that some of the selenoproteins have anti-viral properties.

Selenium?  A trace element?  You might well ask: How do we know that adequate amounts of dietary and supplemental selenium are important to us?
The first answer is: because we can see that selenium deficiency makes people sick.
A further answer is that we now know that selenium is an essential component of antioxidant enzymes.
And, on the basis of the results of randomized controlled trials, we know that selenium supplementation reduces the risk of cancer, reduces the risk of heart disease, and improves immune function.
Selenium is also very useful for reducing the toxic effects of heavy metals in the body.

Reason number one: Selenium-deficiency diseases
Keshan disease
In the 1960’s and 1970’s, thousands of people living in a region of China with selenium-poor soil, and, consequently, with selenium-poor food, died from the effects of a form of heart disease.  The disease, which took its name from Keshan county in the afflicted region of China, is characterized by inflammation and enlargement of the heart muscle and excess fluid in the lungs. The primary cause of the disease was selenium deficiency.

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Dr. Gerhard N. Schrauzer – renowned selenium researcher

Schrauzer
Dr. Gerhard N. Schrauzer was the first scientist to study the biological functions of selenium systematically. He was known internationally for his pioneering work in the cancer-protective properties of selenium. (Picture: Cancer Research, vol. 49 no. 23, Dec. 1, 1989)

Dr. Gerhard N. Schrauzer was the grand old man of selenium science.  Actually, he was the grand old man of trace element research in the United States for 30 years or more.  He was one of the pioneers and one of the major figures in selenium research.   Let’s take a look at the useful contributions of information to the selenium supplementation knowledge base that Dr. Schrauzer made.

First, who was Dr. Schrauzer in the context of selenium research?
Dr. Schrauzer did his graduate study in chemistry at the University in Munich, Germany. He was awarded his Ph.D. summa cum laude.  From 1966 to 1994, he was a chemistry and biochemistry professor at the University of California in San Diego (UCSD). After his retirement, he was a professor emeritus at UCSD.

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