Selenium and good health. How much do we need? How do we get it? Generally speaking, our family and friends do not know just how important selenium is to good health. Our bodies cannot synthesize selenium. We are dependent upon food for an adequate daily intake of this essential trace element.
Vegetarians and vegans, do they get enough selenium in their diets? It is an important question because the number of vegetarians around the world is growing for ethical and environmental reasons. How do we measure selenium status in various groups of people?
Selenium is an essential trace element. Essential means that we have to get it from our food or from supplements. The human body does not synthesize selenium. What the body does synthesize is the selenoproteins, of which selenium in the amino acid selenocysteine is a key active component.
Particularly in much of Europe and the Middle East, the soil and the plants have relatively poor selenium content. In many countries, the farm animals are supplemented with selenium to improve their nutritional intakes and their health and to avoid selenium deficiency syndromes.
Selenium is a trace element essential for for DNA repair, for good immune function, and for reduced mortality risk.
The Micronutrient Information Center maintained by staff members at the Linus Pauling Institute of the Oregon State University provides reliable information about the vitamins and minerals and trace elements used in nutritional supplements.
Today, I want to summarize the information that the Center provides about selenium and supplement that information with the latest scientific research.
Selenium is a trace element that is essential that humans need for the proper functioning of selenium-dependent selenoproteins. Free selenium is rare in the body. Instead, the selenium in the body is typically a component of selenomethionine, selenocysteine, and methyl-selenocysteine.
Many people in the world live in regions with selenium-poor soil and, consequently, with selenium-poor food. The body cannot synthesize selenium, which is an essential non-metal trace element that we need in small amounts. A recent review of selenium status and the risk of cardiovascular disease suggests that serum selenium status below 100 mcg/L is associated with increased risk of heart disease, with reduced exercise capacity, with reduced quality of life, and with worse prognosis [Al-Murbarak].
Stoffaneller and Morse conducted a comprehensive study – 143 references – of selenium status in Europe, the UK, and the Middle East. They concluded that selenium intake and status are generally suboptimal in European and Middle Eastern countries, with somewhat more variation in the Middle East. They reported that suboptimal selenium status is widespread throughout Europe and the UK, with Eastern European countries having lower selenium intakes than Western European countries. In the Middle Eastern countries, they found varying results, which were possibly caused by different food habits and different imports in different regions and within differing socioeconomic groups [Stoffaneller & Morse].
China and Corona Virus will be forever linked in our minds. However, there is another important connection that we should be making: selenium status and its effect on COVID-19 virus in China.
Let me explain. Chinese and American and British researchers have published a letter in the American Journal of Clinical Nutrition in which they report evidence of a significant association between regional selenium status and the reported cure-rate of COVID-19 infected patients in China [Zhang 2020].
The researchers’ data show a statistically significant association between the reported cure-rates for COVID-19 virus infections and selenium status in China [Zhang 2020].
Beginning in mid-February 2020, the researchers collected data from the Baidu website, which they describe as a non-governmental website that provides daily updates of reports from the health commission of each province in China.
We want, all of us, to stay as young and healthy as possible as late in life as possible. Ageing is inevitable. How can we delay the onset of ageing’s bio-chemical and physiological consequences?
The authors of a 2019 review article have found that, overall, there is an inverse correlation between age and blood selenium levels. Higher age is associated with lower blood selenium concentrations [Robberecht 2019].
Inadequate dietary intakes of selenium and poor selenium status (< 85 micrograms per liter in blood) may increase the risk of following harmful health outcomes [Robberecht]:
A variety of factors must be taken into consideration when we investigate the relationship between ageing and selenium intake and status. There are, first of all, considerable regional variations in the availability of selenium in the soil and in foodstuffs [Stoffaneller & Morse].
Selenium is an important trace element that is needed for the proper functioning of our cells. It is needed in very small amounts, but it might be a good idea to have a blood test done to check the serum selenium level.
The Mayo Clinic Laboratories state that the normal concentration in adult human blood serum is 70 to 150 micrograms per liter (the same as 70 to 150 nanograms per milliliter). According to the Mayo Clinic, the US population mean value is 98 micrograms per liter [Mayo Clinic].
Diet, geographic location, demographic factors, and environmental factors all influence serum selenium levels.
The following factors are independent predictors of higher selenium status in the United States [Park]:
Professor Rayman lists a number of conditions that have been associated in the research literature with selenium deficiency:
Professor Rayman does not specify a plasma/serum selenium level for selenium deficiency.
She does mention a US National Health and Nutrition Examination Survey that measured the serum selenium levels in 13,887 adult participants and then followed up for mortality for up to 18 years. The mortality in that study showed a U-shaped association between serum selenium and death, with a serum selenium concentration of 135 micrograms per liter at the bottom of the U [Rayman 2019].
Selenium is a trace element. It exists only in rare quantities in the world. It is produced primarily as a by-product of the process of mining copper. It is not recyclable. It is very unevenly distributed in the soils of the earth.
Consequently, the availability of selenium in grasses and grains and, at the next stage of the food chain, in animals, varies considerably from region to region in the world. The human dietary intakes of selenium vary accordingly around the world.
Selenium a vital nutrient for humans
Selenium is a necessary micronutrient that our bodies do not produce. We get our selenium primarily from our diets. Selenium is important for good immune system function, good thyroid function, good reproductive function, and good protection of our cells’ DNA.
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.
