Selenium is an essential trace element, essential in the sense that our bodies cannot synthesize it, and we must get what we need of it in our diets.
Suboptimal intakes of selenium, i.e., intakes below the recommended intake levels, are associated with increased disease risks, in particular increased risk of autoimmune diseases, chronic diseases, inflammation, etc.
Unfortunately, the health risks of selenium deficiency are often neglected. Here are some facts:
- Preventable endemic diseases are known in regions with selenium deficiency, e.g., in certain parts of China.
- Sufficiently high selenium status is a prerequisite for adequate immune system response.
- Individuals living in regions with selenium-poor soil, women who are pregnant, individuals with autoimmune thyroid disease, and individuals with a severe illness, e.g. COVID-19, are known to have sub-optimal selenium intakes and status.
- Improved dietary choices and/or selenium supplementation are efficient ways to avoid severe selenium deficiency.
These are the major points in a recent journal article published by Professor Lutz Schomburg, Charité–Universitätsmedizin Berlin, Freie Universität Berlin, and Humboldt Universität zu Berlin.
Selenium and Selenoproteins
The micronutrient selenium is a component of the amino acid selenocysteine, which is itself an essential part of some 25 selenoproteins identified in human biology. Some selenoproteins are known to be essential for life; accordingly, they are preferentially synthesized and distributed. The brain, for example, has high priority for selenium in times of scarcity.
A sufficiently high selenium intake is needed to improve selenoprotein expression levels and to raise the selenium status in the cells and tissues that are low in priority for selenium supply during periods of low selenium intakes, e.g., the liver, the muscle, the gastrointestinal tract, and the immune system.
Selenium Status and Disease Risk
The information presented below comes from the 2021 review article written by Professor Schomburg.
Selenium Status and Hashimoto’s Thyroiditis
Hashimoto’s thyroiditis is a highly prevalent autoimmune disease; it is more prevalent in women than in men. Its incidence is high and is increasing.
Professor Schomburg notes that conclusive evidence for a
causal role of selenium deficiency in the promotion of hypothyroidism
has been seen in a large cross-sectional study in China that enrolled more than 6000 subjects who lived either in a selenium-deficient area or in a moderate selenium status area.
A randomized controlled trial conducted in Italy tested supplementation with 200 mcg of selenium daily in pregnant women with or without positive TPO-aAb auto-antibodies. The selenium intervention successfully reduced the risk of both post-partum thyroid disease and permanent hypothyroidism. No side effects were recorded.
Selenium Status and Graves’ Disease
Graves’ Disease is the second major form of thyroid autoimmune disease, second to Hashimoto’s Disease. It causes symptoms of hyperthyroidism, and it too is more prevalent in women than in men. The relationship between selenium status and Graves’ Disease is less-well understood than is the relationship in Hashimoto’s Disease.
In the large Chinese study mentioned above, only the male subjects had a higher prevalence of Graves’ Disease in the low selenium area, compared to the men in the higher selenium intake area; the Graves’ Disease prevalence of the women was largely unaffected by the difference in the selenium. The difference in the female-to-male ratio of hyperthyroidism between the selenium-poor area and the moderate selenium area was statistically significant [Wu 2015].
With respect to selenium intakes, Professor Schomburg cites one randomized controlled trial in which a six-month-long intervention with selenium had positive health effects in Graves’ orbitopathy. The selenium intervention was associated with suppression of the protrusion of the eyeball and suppression of inflammatory bio-markers; the daily selenium supplementation was associated with improved eye motility and improved quality of life [Marcocci 2011].
Selenium Status and Type 1 and Type 2 Diabetes Mellitus
Type 1 diabetes mellitus is the autoimmune form of diabetes that develops primarily at a young age, but it can also occurs as a slowly developing autoimmune diabetes in adults or as an abrupt adult-onset type 1 diabetes.
It is characterized by a progressive destruction of the insulin-producing pancreatic beta cells; insulin replacement therapy is necessary.
Estimates are that about one in ten cases of diabetes mellitus is caused by autoimmune disease; the majority of diabetes cases are associated with insulin insensitivity, overweight, and older age, and are known as type 2 diabetes mellitus. There are different but overlapping categories of diabetes mellitus, a fact that makes personalized diagnosis and treatment a must.
Increased serum or plasma selenium levels have been observed in many type 2 diabetes patients. Professor Schomburg explains that, when individuals develop type 2 diabetes, there results a disruption of the normal regulation of the bio-synthesis of Selenoprotein P in the liver, which, in turn, causes higher serum Selenoprotein P and selenium concentrations in the blood.
Professor Schomburg asserts that the data from large and well-designed randomized controlled trials indicate that selenium supplementation is not causally related to a higher incidence of type 2 diabetes mellitus. He suggests that it may be the other way around: high serum selenium levels result from the development of diabetes [Schomburg 2020].
Selenium Status and Rheumatoid Arthritis
A third major group of inflammatory and chronic autoimmune diseases is rheumatoid arthritis, which affects primarily the joints but can spread to major organs in the body. It also affects women more than men; it tends to peak in late adulthood.
Serum selenium status and the status of three bio-markers of selenium status – glutathione peroxidase-3 levels, total selenium levels, and selenoprotein P levels – have been seen to be significantly decreased in rheumatoid arthritis patients relative to the corresponding levels in control subjects. (Deficiency of zinc is also reported in rheumatoid arthritis patients.)
Reduced selenium status is associated with an up-regulation of a number of
inflammation-relevant genes. The chronic inflammation associated with rheumatoid arthritis seems to impair selenium metabolism and to impair the bio-synthesis of selenoprotein P in the liver, which results in a decline in serum selenium status in rheumatoid arthritis patients compared to healthy controls.
Anti-rheumatic treatment has shown a positive effect on selenium status, and the increase in selenium status is paralleled by a reduction in inflammatory activity.
For unknown reasons, selenium supplementation of rheumatoid arthritis patients has not been investigated extensively or systematically. There have been a few intervention studies with supplemental selenium, but they have been characterized by small groups of patients, short duration, and a limited monitoring of biomarkers of selenium status.
Bottom Line: Selenium Status and autoimmune Disease Risk
We need sufficient intakes of the trace element selenium for normal functioning of the immune system.
Sub-optimal selenium status can impair immune responses and make us vulnerable to autoimmune diseases, e.g., autoimmune diseases of the thyroid gland.
Moreover, elevated cytokine levels in an active immune system can have a dampening effect on the biosynthesis of selenoproteins in the liver and on the secretion of selenoprotein P into the blood circulation, resulting in reduced selenium metabolism and suppressed selenium status.
Avoiding severe selenium deficits may reduce the risk of autoimmune diseases and may alleviate disease symptoms.
Thus, selenium substitution is strongly recommended for acute or chronic deficiency.
At the present time, selenium supplementation for healthy subjects with sufficiently high baseline levels does not appear to be necessary.
Note: Bomer et al. [2019 ]have shown that serum selenium status below 70 mcg/L is clearly associated with more severe signs and symptoms of heart failure, poorer exercise capacity, and worse quality of life. In their study, heart failure patients with serum selenium levels below 100 mcg/L also had noticeably poorer exercise capacity and worse quality of life than patients with higher serum selenium concentrations.
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Mao J, Teng W. The relationship between selenoprotein P and glucose metabolism in experimental studies. Nutrients. 2013;5:1937–1948.
Marcocci C, Kahaly GJ, Krassas GE, Bartalena L, Prummel M, Stahl M, Altea MA, Nardi M, Pitz S, Boboridis K et al. Selenium and the course of mild Graves’ orbitopathy. N. Engl. J. Med. 2011;364:1920–1931.
Schomburg L. Selenium deficiency due to diet, pregnancy, severe illness, or covid-19—a preventable trigger for autoimmune disease. Int. J. Mol. Sci. 2021;22(16):8532.
Schomburg L. The other view: The trace element selenium as a micronutrient in thyroid disease, diabetes, and beyond. Hormones
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Speckmann B, Sies H, Steinbrenner H. Attenuation of hepatic expression and secretion of selenoprotein P by metformin. Biochem. Biophys. Res. Commun. 2009, 387, 158–163.
Wu Q, Rayman MP, Lv H, Schomburg L, Cui B, Gao C, Chen P, Zhuang G, Zhang Z, Peng X, et al. Low Population selenium status is associated with increased prevalence of thyroid disease. J. Clin. Endocrinol. Metab. 2015;100: 4037–4047.
The information presented in this article is not intended as medical advice; it should not be construed as such.
15 September 2021