Category: Selenoproteins

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Regional, age, and sex differences in serum selenium status

Selenocysteine is the 21st amino acid. The trace element selenium plays its important biological roles in the body as a component of selenocysteine. Selenocysteine is found in at least 25 selenoproteins including selenoprotein P and the various glutathione peroxidases, thioredoxin reductases, and iodothyronine deiodinases.

The results of clinical studies give us an estimate of what an individual’s optimal serum or plasma selenium status is.

  •  Plasma selenium status below 100 micrograms per liter  – also expressed as 100 nanograms per milliliter – is generally regarded as sub-optimal plasma selenium status [Hurst 2010].
  • Plasma selenium status of at least 110 – 118 micrograms per liter is considered necessary for the optimal expression of selenoprotein P [Hurst 2010]. 
  • Letsiou et al [2014] set the lower limit for optimal selenoprotein P activity at 120 micrograms per liter or higher.
  • Plasma selenium status of 120 up to 170 micrograms per liter is considered necessary for reducing the risk of prostate cancer [Hurst 2012].
  • Studies show that there are sex and age differences in the absorption and distribution of selenium taken in from the diet and from supplements [Letsiou 2014; Galan 2005].

Note: The Mayo Medical Laboratories report serum concentrations of 70 to 150 micrograms per liter as the adult reference range for residents of the United States.  The mean population serum concentration is 98 micrograms per liter [Mayo], but, remember, depending on the range and standard deviation of the data, the mean can be very little useful. The important thing about the United States is that there is regional variation in selenium intakes and status. See below.

Selenium intake and selenium status

The primary sources of selenium are the diet and supplements. The human body does not synthesize selenium.  It is difficult to calculate accurately how much selenium an individual gets from food.  It can also be difficult to know precisely how much selenium an individual absorbs from a supplement because of the variation in the form and formulation of the selenium supplements on the market. read more

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Selenium and statin medications and selenoproteins

Adequate synthesis of several selenoproteins – including the various glutathione peroxidases and thioredoxin reductases and Selenoprotein P – is important for the anti-oxidative defense of the cells. Professor Urban Alehagen and a group of Swedish researchers observed significantly reduced death from heart disease in a 10-year follow-up of healthy elderly study participants who were given four years of combined high-selenium yeast and Coenzyme Q10 supplementation.

In a recent article on the web-site q10facts.com, I have posted a summary of an article in which researchers discuss the various ways in which statin medications may increase patients’ risk of atherosclerosis and heart failure.  Yes, the Japanese and American researchers say, the statin medications do lower cholesterol levels [Okuyama].  

But, the guidelines for the use of statin medications need to be re-examined.  The researchers say: There has been a remarkable increase in the incidence of heart failure in the same period that statin medications have been used [Okuyama].

Furthermore, there are known mechanisms by which statin medications could be causing an increase in the incidence of atherosclerosis and heart failure. read more

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Selenium supplementation in the Su.Vi.Max. study

Depicted above (A): apoptosis in normal cell division with a damaged cell (2) and programmed cell death (1). Depicted below (B): cancer cell division with uninhibited cell production and increasingly more dangerous cell mutations. Selenium supplementation can help normal healthy adults who have low selenium status with cancer chemo-prevention benefits, thyroid function benefits, and cognitive function benefits.

The Su.Vi.Max. study —  SUpplementation en VItamines et Minéraux AntioXydants — was a big randomized, double-blind, placebo-controlled study carried out with typical French efficiency.  Even though I have written the name of the study in French, there are so many English cognates that I am sure you can read the full name of the study.

The study was designed to test the health benefits of daily supplementation with a number of vitamins and minerals at nutritional dosages (roughly, one to three times the daily recommended dietary intakes) [Hercberg 1998]:

  • selenium, 100 micrograms
  • vitamin C, 120 mg
  • vitamin E, 30 mg
  • beta-carotene, 6 mg
  • zinc, 20 mg

In particular, the French researchers wanted to see the effect of the daily supplementation over a long period, approximately 7.5 years, from 1994 to 2002, on the prevention of cancer and cardiovascular disease, both of which have been linked to oxidative stress and oxidative damage and might, therefore, be affected by supplementation with antioxidants. read more

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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]. read more

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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. read more

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A basic guide to selenium

Selenium is a by-product of the mining and refining of copper. There are no sites in the world for the mining of selenium alone. Given its relative scarcity and its many uses — industrial and agricultural as well as nutritional — selenium for supplements will surely be more expensive in the future, and there may well be shortages of it in the future. Accordingly, it is important for us to use it wisely and to conserve it.

Selenium is an important micronutrient.  It is essential for life for both people and animals.  The body cannot synthesize selenium and is dependent upon the selenium that it can get from food.  In many regions of the world, there is too little selenium in the soil and in the food, and supplementation is necessary for optimal health.

Regions with selenium-poor soil
In many regions of the world, the content of selenium in the soil is quite low.  In large parts of Asia, China in particular, and in much of Europe and the Middle East, there are low levels of selenium in the soil.

Plants accumulate inorganic selenium from the soil and convert it to organic selenium. In that way, the selenium enters the food chain. For example, cows eat grass containing selenium, and the some of the selenium enters the meat and the milk of the cows.  People eat the meat and drink the milk.  Too little selenium in the soil means too little selenium in the food. read more

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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]. read more

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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. read more

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The functions of selenium supplements

skin-cells antioxidant
Selenium is an important component of the antioxidant defense in the cells. It helps to protect against oxidative damage to both cells and DNA. It has been shown to have a protective effect against the damage to skin cells caused by ultraviolet radiation.

Why the interest in selenium facts?  Here, at the beginning of the seleniumfacts.com website, we want to review in broad terms what we know about the functions of selenium supplementation. We are especially interested in selenium’s antioxidant and anti-inflammatory effects in the human body.

Selenium is an essential trace element in the human diet, and, in many regions of the world, it is an absolutely necessary nutritional supplement.  It has many and diverse functions in the human body.

One of the interesting things about selenium is that it does not perform its functions as an element or an ion.  Instead, it functions as a component of more complex compounds.  In particular, it is an essential component of the 21st amino acid, selenocysteine. read more

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Moderate selenium deficiency may increase risk of chronic disease

Pill, hand, disease
A supplement of 100 micrograms of elemental selenium a day is able to satisfy the needs of the most critical selenoproteins.

Moderate selenium deficiency is associated with increased risk of chronic disease: cancer, heart disease, thyroid disorder.  Conversely, a selenium supplement containing one hundred (100) micrograms of selenium  daily could reduce the risk of serious, age-related diseases in persons with moderate selenium deficiency, according to the known researcher Bruce Ames’ so-called triage theory.

Researchers Joyce McCann and Bruce Ames from Children’s Hospital Oakland Research Institute (CHORI) have analyzed the data from hundreds of scientific articles. They conclude that some selenium-dependent proteins that are regarded as essential for the body’s survival in the period until humans reach reproductive age are much more resistant to selenium deficiency than are other non-essential selenoproteins. read more