by David E Marsh
Link to original article in Positive Health Online 263, June 2020.
Even though selenium is critically important for good human health, its value is not widely known. It is important both for the prevention of selenium-related deficiency diseases and for its health promoting biological functions as part of the amino acid selenocysteine that is incorporated into the selenoproteins. One of its most important roles is essentiality helping with the repair of faulty DNA, which is why selenium deficiency is so often associated with cancer.
Native selenium in sandstone, from a uranium mine near Grants, New Mexico
Selenoproteins are proteins containing selenium in the form of the 21st amino acid, selenocysteine. Members of this protein family have many diverse functions, but their synthesis is dependent on a common set of co-factors and on dietary selenium. Although the functions of many selenoproteins are unknown, several disorders involving changes in selenoprotein structure, activity or expression have been reported. Selenium deficiency and mutations or polymorphisms in selenoprotein genes and synthesis cofactors are implicated in a variety of diseases, including muscle and cardiovascular disorders, immune dysfunction, cancer, neurological disorders and endocrine function. Members of this unusual family of proteins have roles in a variety of cell processes and diseases. Among these, the immune dysfunctions seem to include the DNA repair system, so incorrect copies of genes give rise to cancers and other virulent viruses, as referred to by Margaret Rayman et al, below:
Large parts of Europe and the Middle East, Africa, Asia, and New Zealand are known to have low selenium concentrations in the soil and in the locally grown food. Similarly, large parts of certain regions of the United States – the Northeast, the Southeast, the Northwest, and the Southwest – have lower than average selenium concentrations in the soil and in the locally produced foodstuffs. Areas of SW South America are likewise deficient.
Soils worldwide became impoverished in the 20th century through artificial fertilizer use and intensive agriculture. Plants cannot make minerals, being able only to obtain minerals from the soil. Artificial fertilizers contain only nitrogen N, phosphate P and K potash; occasionally some soils get lime: fertile soils contain upwards of 60 minerals, as does the blood of mammalian species. Mineral starved soil produces mineral-deficient crops, fodder and animal and human populations with poor health and poor immune function. Specific types of basalt (volcanic) rock contain 80 plus minerals and trace elements and are widely available.
Selenium is a key mineral required for metabolism. The mineral is naturally found in water, and several foods and is required for longevity and optimal health. The trace mineral is beneficial for improving immunity and as it is an essential mineral, it has to be obtained through selenium-rich foods. The selenium requirement of the body is in tiny quantities, however, it is critical to the proper functioning of the body. The mineral is of two types, organic and inorganic. That is, selenium can also be acquired through supplements.
Regular consumption of selenium helps create a protective layer around your body, which helps guard your body against various diseases.
Selenium is incorporated into selenoproteins that have a wide range of pleiotropic effects*, ranging from antioxidant and anti-inflammatory effects to the production of active thyroid hormone. In the past 10 years, the discovery of disease-associated polymorphisms in selenoprotein genes has drawn attention to the relevance of selenoproteins to health. Low selenium status has been associated with increased risk of mortality, poor immune function, and cognitive decline. Higher selenium status or selenium supplementation has antiviral effects, is essential for successful male and female reproduction, and reduces the risk of autoimmune thyroid disease.
* Pleiotropic effects occur when one gene influences two or more seemingly unrelated phenotypic traits. Such a gene that exhibits multiple phenotypic expression is called a pleiotropic gene. Mutation in a pleiotropic gene may have an effect on several traits simultaneously, due to the gene coding for a product used by a myriad of cells or different targets that have the same signalling function.
Mammals have a mechanism to repair faulty DNA which needs selenium for the mechanism to work, which is why it is associated with cancer.
Low selenium in selenoprotein genes has drawn attention to the relevance of selenoproteins to health. Low selenium status has been associated with increased risk of mortality, poor immune function, and cognitive decline. Higher selenium status or selenium supplementation has antiviral effects, is essential for successful male and female reproduction, and reduces the risk of autoimmune thyroid disease.
Prospective studies have generally shown some benefit of higher selenium status on the risk of prostate, lung, colorectal, and bladder cancers, but findings from trials have been mixed, which probably emphasizes the fact that supplementation will confer benefit only if intake of selenium is inadequate. Supplementation of people who already have an adequate intake with additional selenium might increase their risk of type-2 diabetes. The crucial factor that needs to be emphasized with regard to the health effects of selenium is the inextricable U-shaped link with status; whereas additional selenium intake may benefit people with low status, those with adequate-to-high status might be affected adversely and should not take selenium supplements.
Excessive intakes of selenium can be toxic, although it is unlikely for one get too much selenium from diet alone. Toxicity typically occurs from overdose of supplements. You can safely have as much as 400 micrograms of selenium per day, which is the established tolerable upper intake level, or UL. Four ounces of salmon only has about 10 percent of this amount. Early selenium toxicity leads to brittle nails and hair loss. In severe cases, you may experience gastrointestinal upset, garlic breath, skin rashes and neurological problems.
Consuming foods that have a naturally high content of selenium helps benefit your body in various ways. Some of the natural sources of selenium are mentioned below (mcg per 100 gram).
|Brazil nuts||1917 mcg|
|Yellowfin tuna||36.5 mcg|
|Pork chops||33.8 mcg|
|Lean chicken breast||31.9 mcg|
|Whole wheat pasta||73 mcg|
|Shiitake mushrooms||24.8 mcg|
|Sunflower seeds||53 mcg|
|Chia seeds||55.2 mcg |
In his article, "Food quality and its relevance to optimum health", Dr David Thomas, says
"It seems I’ve been banging on about the dangers to general health of mineral deficiencies in foods for over 25 years and at long last, the significance of the micronutrient content of foods has begun to find traction. Now, in addition to the physical composition of foods, I have become more aware of less quantitative, more qualitative aspects of foods. I feel there’s need to conduct future research work into their significance – and maybe this can ultimately lead to a more inclusive less reductionist scientific paradigm than is currently in vogue."
Referring to his acclaimed study between the several publications of McCance and Widdowson 1940-1991 Dr Thomas asks “Is there more to the quality of foods than their micronutrient content?
Commenting on the above, Dr Thomas says
"To put the significance of these findings into perspective, let’s consider the European Nutrient Reference Values (NRV) for magnesium (375mg), zinc (10mg), chromium (40μg) and selenium (55 mcg), which many nutritionists consider to be the minimums below which deficiency diseases begin to manifest. How much is this actually per day? Given that a level teaspoon represents 5mg, 1/13th of a level teaspoon would represent the magnesium quota; 1/500th is the requirement for zinc; while approximately a 1/125,000th of a teaspoon is all that is required for chromium. In relationship to the amount of food we eat each day, these are minuscule amounts: yet deficiencies do indeed occur. Consequently, micronutrient content can be considered one fundamental signifier of a food’s nutritional quality.
“Deficiencies of micronutrient content in food have been linked in part to declining soil quality".[6,7,8]
Selenoproteins are proteins containing selenium in the form of the 21st amino acid, selenocysteine. Members of this protein family have many diverse functions, but their synthesis is dependent on a common set of co-factors and on dietary selenium. Although the functions of many selenoproteins are unknown, several disorders involving changes in selenoprotein structure, activity or expression have been reported. Selenium deficiency and mutations or polymorphisms in selenoprotein genes and synthesis cofactors are implicated in a variety of diseases, including muscle and cardiovascular disorders, immune dysfunction, cancer, neurological disorders and endocrine function. Members of this unusual family of proteins have roles in a variety of cell processes and diseases. Among these, the immune dysfunctions seem to include the DNA repair system, so incorrect copies of genes give rise to cancers and other virulent viruses, as referred to by Margaret Rayman et al, below: 
Publishing their findings in the American Journal of Clinical Nutrition, researchers using data (up to 18 February), investigated possible links between selenium levels in the body and cure or death rates of those with the COVID-19 virus in China.
Selenium is an essential trace element obtained from the diet (i.e. fish, meat and cereals) which has been found to affect the severity of a number of viral diseases in animals and humans. For example, selenium status in those with HIV has been shown to be an important factor in the progression of the virus to AIDs and death from the condition. China is known to have populations that have both the lowest and highest selenium status in the world, due to geographical differences in the soil which affect how much of the trace element gets into the food chain.
Margaret Rayman, professor of nutritional medicine at the University of Surrey, said; "Given the history of viral infections associated with selenium deficiency, we wondered whether the appearance of COVID-19 in China could possibly be linked to the belt of selenium deficiency that runs from the north-east to the south-west of the country?
“Examining data from provinces and municipalities with more than 200 cases and cities with more than 40 cases, researchers found that areas with high levels of selenium were more likely to recover from the virus. For example, in the city of Enshi in Hubei Province, which has the highest selenium intake in China, the cure rate (percentage of COVID-19 patients declared 'cured') was almost three times higher than the average for all the other cities in Hubei Province. By contrast, in Heilongjiang Province, where selenium intake is among the lowest in the world, the death rate from COVID-19 was almost five-times as high as the average of all the other provinces outside of Hubei”.
Most convincingly, the researchers found that the COVID-19 cure rate was significantly associated with selenium status, as measured by the amount of selenium in hair, in 17 cities outside of Hubei.
Kate Bennett, a medical statistician at the University of Surrey, said;
"There is a significant link between selenium status and COVID-19 cure rate, however, it is important not to overstate this finding; we have not been able to work with individual-level data and have not been able to take account of other possible factors such as age and underlying disease."
Ramy Saad, a doctor at Royal Sussex County Hospital, Brighton, currently taking an MSc degree in Nutritional Medicine at the Department of Nutritional Sciences at Surrey, commented;
"The correlation we have identified is compelling, particularly given previous research on selenium and infectious diseases. As such, a careful and thorough assessment of the role selenium may play in COVID-19 is certainly justified and may help to guide ongoing public-health decisions."
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Maps Illustrate the Modelled Soil Se Concentrations 1980.
SOC – Soil Organic Carbon
Source: Gerrad D. Jones,aBoris Droz,aPeter Greve,bPia Gottschalk,cDeyan Poffet,a,dSteve P. McGrath,eSonia I. Seneviratne,bPete Smith,f and Lenny H. E. Winkela,d,1 Selenium deficiency risk predicted to increase under future climate change Proc Natl Acad Sci U S A.© 2017 Mar 14; 114(11): 2848–2853. Published online doi: 10.1073/pnas.1611576114. Feb 21 2017.
Following many decades of producing food in greater and greater quantities, regardless of its quality, has resulted in worn soils producing inferior quality food for crops, forage, livestock and human populations with weakened immune systems unable to survive when faced with new variants of bacteria and viruses.
When considering the vast deserts of selenium deficient soils worldwide, we can but expect new variants of existing problematic bacterial and viral strains to appear. Indeed already there are reports of two new strains of Covid-19.
Agronomists and medical experts worldwide need to consider repairing the qualities of soil and the food it produces, for the truth of what one of our greatest medical experts of the recent times, the late Sir Robert McCarrison taught, that healthy food comes from healthy soils. We also need to re-examine the wisdom of our current neo-Darwinian theory of evolution in the light of our rapidly expanding knowledge of nutrition, particularly in the fields of long-chain fatty acids, genetics and epigenetics, to help us understand why we have made such an appalling mess of our environment over the last century.[12, 13, 14, 15]
1. Survival of Civilisation_ Hamaker & Weaver: World Wide Web Edition. Soilandhealth.org 1982. Remineralize the Earth. 2002.
2. Rayman, M. P. The importance of selenium to human health. The Lancet, 356 2. 9225, 233-241.2 DOI: https://doi.org/10.1016/S0140-6736(00)02490-9 2000.
3. Rayman, M. P. Selenium and human health.The Lancet, 379(9822), 1256-1268. 2012.
4. UK soils are deficient in Selenium – Farmers weekly Friday 30 March 2007.
5. Finley, J. W. (2006). Bioavailability of selenium from foods. Nutrition reviews,64(3), 146-151. See also “Lesser Known Benefits Of Selenium For Health, Skin And Hair” By Amritha Kon January 23, 2019.
6. Thomas DE. The mineral depletion of foods available to us as a nation over the period 1940 to 2002, Nutrition and Health, 19, 21–55.] 2007.
7. Thomas DE. A study of the mineral depletion of foods available to us as a nation over the period 1940 to 1991. Nutrition and Health, 17, 85–115. Dr Thomas is a Founder Member of the Register of Nutritional Therapists]. 2003.
8. Thomas DE, Journal of holistic healthcare. Volume 16 Issue 3 Autumn 2019.
9. Frederick P. BELLINGER,1 Arjun V. RAMAN, Mariclair A. REEVES, and Marla J. BERRY. Biochem J: 422(1): 11–22. Regulation and function of selenoproteins in human disease. Jul 29 2009.
10. M RAYMAN et al. Link identified between dietary selenium and outcome of COVID-19 disease by University of Surrey. Credit: CC0 Public Domain.
11. More information: Jinsong Zhang et al. Association between regional selenium status and reported outcome of COVID-19 cases in China, The American Journal of Clinical Nutrition (2020). DOI: 10.1093/ajcn/nqaa095 Journal information: American Journal of Clinical Nutrition. Provided by University of Surrey. 2020.
14. Research Article https://doi.org/10.1177/0260106012437548 Darwin’s passionate environmentalism or the dangerous fallacy of the ‘All-sufficiency of natural selection’ theory. Jan 1 2012.
15. Gerrad D. Jones,aBoris Droz,aPeter Greve,bPia Gottschalk,cDeyan Poffet,a,dSteve P. McGrath,eSonia I. Seneviratne,bPete Smith,f and Lenny H. E. Winkela,d,1 Selenium deficiency risk predicted to increase under future climate change Proc Natl Acad Sci U S A.© 2017 Mar 14; 114(11): 2848–2853. Published online doi: 10.1073/pnas.1611576114. Feb 21 2017.