Selenium Status and Viral Infections

Selenium and viral infections, what do we know?

Selenium is a micronutrient that is essential for good health.
Low serum selenium status (below 85 microg/mL) and marginal serum selenium status (between 85 and 100 microg/mL) are common in many regions of the world, especially in many parts of Europe, the Middle East, China, and East Asia.
Selenium status is a key factor regulating the immune response to viral infections [Hiffler 2020].
Selenium status influences the immune system response to the severe acute respiratory syndrome corona virus infections [Bermano 2020].
Selenium status is a risk factor that could well influence the outcome of a Covid-19 infection, particularly if the infected individuals have a sub-optimal or low selenium intake [Bermano 2020].
Selenium supplementation may limit the severity of Covid-19 infections, particularly in regions in which the selenium intake is low [Bermano 2020, Hiffler 2020].

Evidence for a Link Between Selenium Status and Viral Infection Severity

The early evidence came from study of the Keshan Disease in China – caused by the combination of the coxsackie B3 virus and low selenium status. By adding selenium to the soil fertilizer and by encouraging the use of selenium supplements, Chinese authorities have been able to reduce significantly the incidence of the disease [Bermano 2020].

Then came evidence from mouse studies that showed that there is increased virulence to coxsackie and influenza viruses in hosts with low selenium status [Bermano 2020].

Next came evidence that low selenium status, commonly seen in HIV-infected patients, is associated with reduced numbers of CD4 T cells and with increased disease progression and death rates [Bermano 2020].

Finally, in a human study, volunteers with marginal selenium status (plasma selenium below 95 microg/L) were given a weakened polio virus. Selenium supplementation increased the rate at which the polio virus was cleared from the body and decreased the rate at which virus mutated. Moreover, selenium supplementation was seen accelerate the cellular antiviral response [Bermano 2020].

Selenoproteins and Immune Response to Viral Infections

There is evidence that the Covid-19 virus induces increased oxidative stress, increased cytokine/inflammatory activity, reduced mitochondrial function and reduced cell respiration processes, and disturbances in the orderly degradation and recycling of cellular components [Bermano 2020].

Sufficient selenium status is needed to synthesize the antioxidant selenoproteins – the glutathione peroxidases and thioredoxin reductases – to counteract oxidative stress.
Glutathione peroxidase-1, glutathione peroxidase-4, and thioredoxin reductase-1 are needed for the maintenance of mitochondrial function and redox homeostasis.
Selenium status affects a range of inflammatory mechanisms; accordingly, individuals with low selenium status may have an inadequate inflammatory response to viral infections.

Covid-19 Severity and Selenium Status in China

A study done in China has shown that the overall cure-rate for Covid-10 patients is higher in patients with higher selenium status as assessed by hair selenium concentrations; the death rate is higher in patients with low selenium status [Zhang 2020].

Covid-19 Mortality and Selenium Status in Germany

A German study has shown the following relationships [Moghaddam 2020]:

Covid-19 patients generally have significantly low serum selenium status.
Patients with severe Covid-19 infections are likely to have especially low selenium status, e.g. less than 45 micrograms per liter.
Serum selenium levels are significantly lower in non-survivors than in survivors of Covid-19.

Take-Home Message: Selenium Supplementation and Viral Infections

Selenium protects against viral infections and supports good immune response.
Selenium status is a factor in determining the outcome of a viral infection.
Low selenium status (less than 100 microg/L) is associated with more severe manifestations of virus infections.
Higher selenium status (greater than 100 microg/L) is associated with an enhanced immune response to viral infections.
The impact of selenium and selenoproteins on the immune response to viral infections is related to the role of selenoproteins in cellular mechanisms for the control of redox homeostasis, stress response, and inflammatory response [Bermano 2020].

Sources

Bermano G, Méplan C, Mercer DK, Hesketh JE. Selenium and viral infection: are there lessons for COVID-19? Br J Nutr. 2020;1-37.

Hiffler L & Rakotoambinina B. Selenium and RNA virus interactions: potential implications for SARS-CoV-2 infection (Covid-19). Frontiers in Nutrition. 2020;7:164.

Moghaddam A, Heller RA, Sun Q, et al. Selenium Deficiency Is Associated with Mortality Risk from COVID-19. Nutrients. 2020;12(7):2098.

Rayman MP. Selenium and human health. Lancet. 2012;379(9822):1256-1268.

Rayman MP. Selenium intake, status, and health: a complex relationship. Hormones (Athens). 2020;19(1):9-14.

Richie JP Jr, Das A, Calcagnotto AM, et al. Comparative effects of two different forms of selenium on oxidative stress biomarkers in healthy men: a randomized clinical trial. Cancer Prev Res (Phila). 2014;7(8):796-804.

Zhang J, Taylor EW, Bennett K, Saad R, Rayman MP. Association between regional selenium status and reported outcome of COVID-19 cases in China. Am J Clin Nutr. 2020;111(6):1297-1299.

The information presented in this review article is not intended as medical advice and should not be used as such.

30 September 2020

Milestones in early selenium research

1817 Swedish chemist Jöns Jakob Berzelius discovers selenium

1957 Biochemist Klaus Schwarz shows that selenium in microscopic amounts has a vital importance for mammalian health

1969 Professor J.T. Rotruck discovers that selenium has a biochemical role as a component of the antioxidant enzyme glutathione peroxidase

1969 Professors R.J. Shamberger and D.V. Frost report a possible protective effect of selenium against cancer in humans

1973 Professor J.T. Rotruck identifies the enzyme glutathione peroxidase as a selenium-dependent protein

1977 Professor G.N. Schrauzer publishes cancer mortality correlation studies showing an inverse correlation between dietary intakes of selenium and cancer mortality in 27 countries

1988 Professor G.Q Yang summarizes the lessons learned about the selenium-related endemic diseases Keshan disease and Kashin-Beck disease and about the importance of adequate daily selenium intakes

1989 Professor G.G. Duthie publishes evidence for a role of selenium in the prevention of cardiovascular disease

1993 Researcher W.J. Blot publishes the results of the Nutrition Intervention Trials in Linxian, China, showing that supplementation with a combination of selenium and other antioxidants reduces the risk of cancer

1994 Professor G.N. Schrauzer publishes evidence that selenium is important in the maintenance and therapy of HIV-infected patients

1996 Professor Larry Clark publishes the results of a randomized controlled trial – the Nutritional Prevention of Cancer study -- that shows selenium's cancer-protective effects on colon cancer, lung cancer, and prostate cancer

1997 Professor G.F. Combs summarizes the evidence for the protective effects of selenium against cancer

1999 Professor J.E. Oldfield publishes his Selenium World Atlas, mapping areas of selenium deficiency around the world

2000 Researcher O.A. Levander publishes evidence showing an anti-viral effect of selenium

2002 Researcher R. Gärtner shows that supplementation with selenium reduces inflammation in patients with autoimmune thyroiditis

2002 Researcher Margaret Rayman presents the arguments for increasing selenium intakes to realize selenium’s antioxidant and anti-viral and anti-inflammatory effects as well as selenium’s enhancement of immune function and reproductive success.