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].
Variations in Serum Selenium Levels
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]:
- male gender
- living in the West and Northern-Midwest regions of the US
- consumption of bread and beef products
- use of selenium supplements
Other factors are independent predictors of lower selenium status in the United States [Park]:
- cigarette smoking
- alcohol consumption
- older age
- consumption of eggs, white rice, dairy products, coffee
Regional Variation in Selenium Intakes and Status
United States
Significant geographic variation in selenium status exists in the United States and throughout the world. Given the extensive transport system for food products in the United States, it is somewhat surprising that there is still so much regional variation in the selenium contents of foods in different regions, but several studies have shown regional variation in the selenium content in soils and foodstuffs [Park].
Americans living in the Midwestern states, in the West, and in the South have significantly higher toenail selenium levels than Americans living in other regions of the country. Men living in the northwestern states generally have higher levels of selenium than men living in the southeastern states [Park].
- The highest levels of selenium status are found in Wyoming, South Dakota, North Dakota, Nebraska, and Washington state with serum selenium levels ranging from 94 to 100 micrograms per liter.
- The lowest selenium levels are found in North Carolina, Kentucky, Pennsylvania, Nevada, and South Carolina with serum selenium levels ranging from 75 to 77 micrograms per liter.
There is no evidence that these geographic variations in selenium status are confounded by sex, smoking, or supplement use [Park].
Europe and the Middle East
A 2015 review found that selenium status in Europe and the Middle East is substantially lower, on the whole, than the selenium status in the United States.
The researchers reported sub-optimal selenium status throughout Europe, the United Kingdom, and the Middle East [Stoffaneller & Morse].
- People living in Eastern European countries generally have even lower selenium intakes than people living in Western European countries.
- Estimated daily dietary intakes of selenium in many European countries are below the US recommended dietary intake of 55 micrograms per day.
- Selenium intakes in Middle Eastern countries vary considerably, possibly because of variation in food habits and imports in different regions and within differing socioeconomic groups.
- Estimated daily dietary intakes of selenium in Iran, Jordan, and Turkey are below the US recommended dietary intake of 55 micrograms per day.
- Earlier research showed that at least 98.7 micrograms per liter of selenium in plasma or serum are necessary for optimal activity of the antioxidant enzyme glutathione peroxidase (GPx). With this standard in mind, Stoffaneller and Morse concluded that the selenium intake and status in European and Middle Eastern countries are generally sub-optimal albeit somewhat less consistently so in the Middle East.
Asia and Africa
Many parts of Africa and Asia, in particular parts of China, Korea, Siberia, and Tibet, are known to have low selenium contents in soil and food. The same is true of New Zealand [Haug].
Soil Selenium Fertilization vs Selenium Supplementation
In selenium-poor regions of the world, selenium supplementation is less wasteful and more sustainable that large-scale fertilization programs with selenium-enriched fertilizers similar to the successful soil fertilization program carried out in Finland. Furthermore, there is, seemingly, not enough annual production of selenium to supply large-scale soil fertilization with selenium [Haug].
Note: Please see my article entitled “Selenium Intake and Status Related to Health” for more information about selenium supplementation.
Why We Need Adequate Levels of Selenium
Selenium is a crucial micronutrient because it is incorporated into important selenoproteins and enzymes. These selenoproteins and enzymes are important [Rayman 2004]:
- for antioxidant defense of our cells against oxidative damage
- for reduction of systemic inflammation
- for thyroid hormone production
- for DNA synthesis
- for fertility and reproduction
- for the reduction of the risk of heart disease and some forms of cancer
In a four-year randomized controlled study, Professor Urban Alehagen and a team of researchers from Linköping University investigated the effect of combined daily supplementation of senior citizens with 200 micrograms of high-selenium yeast and 200 milligrams of Coenzyme Q10. The researchers reported the following statistically significant study outcomes:
- reduced mortality from heart disease
- improved heart function
- lower levels of bio-markers for oxidative stress, inflammation, and fibrosis
- improved health-related quality of life
- still reduced levels of mortality from heart disease 12 years after
Selenium deficiency is directly associated with three specific diseases:
- Keshan Disease characterized by an enlarged heart and poor heart function
- Kashin-Beck Disease resulting in osteoarthropathy, a disease of the joints
- Myxedematous Endemic Cretinism resulting in mental retardation
Sources
Haug, A, Graham, RD, Christophersen, OA & Lyons, GH. (2007). How to use the world’s scarce selenium resources efficiently to increase the selenium concentration in food. Microb Ecol Health Dis. 2007 Dec; 19(4): 209–228.
Mayo Clinic Laboratories. (2019). Selenium, serum. Retrieved from https://pediatric.testcatalog.org/show/SES
Park, K, Rimm, E, Siscovick, D, Spiegelman, D, Morris, JS & Mozaffarian, D. (2011). Demographic and lifestyle factors and selenium levels in men and women in the U.S. Nutr Res Pract. 2011 Aug; 5(4): 357–364.
Rayman MP. (2004). The use of high-selenium yeast to raise selenium status: how does it measure up? British Journal of Nutrition, 92, 557-573.
Stoffaneller, R & Morse, NL. (2015). A review of dietary selenium intake and selenium status in Europe and the Middle East. Nutrients. 2015 Feb 27;7(3):1494-537.
The information presented in this review article is not intended as medical advice and should not be used as such.
1 October 2019