Many viruses have been shown to mutate extremely rapidly in selenium deficient patients, causing far more serious symptoms and longer lasting infections.
A great deal of research has been done to understand the role played by selenium in different viral diseases. What’s surprising is that all of the studies show a common link: individuals that are deficient in selenium suffer far more serious viral infections compared with those that have adequate levels of this mineral. Some scientists have suggested that selenium stops viruses changing from low harmful forms into highly destructive (virulent) entities: viruses are more likely to reach their full pathogenic (disease-causing) potential in selenium deficient individuals.
Selenium is a trace element: a mineral that is required by the body in minute quantities to promote normal development and growth. Selenium is needed to make a broad group of proteins called selenoproteins. Some of these proteins are antioxidant enzymes, known as glutathione peroxidases. They protect our cells by neutralising free radicals that can damage DNA. Without selenium, our bodies cannot synthesise selenoproteins, making us more vulnerable to DNA damage.
Figure 1. Individuals that get enough selenium produce antioxidant enzymes called glutathione peroxidases, which are involved in the detoxification of free radicals that cause DNA damage. However, people with selenium deficiency don’t synthesise enough of these important enzymes, as a result they are more prone to DNA damage.
A biological mechanism has been proposed to explain how selenium prevents mild viruses from turning virulent. In selenium deficient individuals, the levels of free radicals are highly elevated, increasing the damage done to the viral genetic material. Shouldn’t this harm the virus? This is usually the case, but sometimes, genetic changes known as mutations can be beneficial, and they may be responsible for transforming mild viruses into deadly ones. Scientists have suggested that viruses undergo these beneficial mutations far more quickly in selenium deficient individuals.
Having adequate levels of selenium may reduce the severity of symptoms in individuals infected by the influenza virus. Research has shown that selenium deficient mice developed significantly more harmful lung inflammation after being infected by influenza virus compared to mice that were fed a selenium adequate diet. Furthermore, the lung inflammation persisted longer in selenium deficient mice. Additionally, the scientists discovered that influenza virus in selenium deficient mice had many gene mutations. Selenium deficiency causes oxidative stress, which induces genetic mutations in the influenza virus. Some of these genetic changes account for the increased disease-causing potential of the virus.
Figure 2. Selenium deficient mice infected with the influenza virus developed far more serious symptoms than mice that were fed a selenium adequate diet. Furthermore the viral genetic material experienced great changes in selenium deficient mice. These genetic modifications may explain why the virus becomes more harmful.
In a region of China called Keshan County, where soil selenium levels are extremely low, many individuals are affected by a fatal heart condition known as Keshan disease. Scientists identified a virus called coxsackievirus as the causing agent of the disease, along with selenium deficiency. A three year study done in the Keshan County highlighted the importance of selenium in Keshan Disease. People were divided into two large groups: individuals in one group were given a weekly selenium supplement while subjects in the other group were given sugar (placebo) pills. The results were impressive: selenium supplementation reduced the incidence of Keshan Disease by 95%! Coxsackie virus is normally a harmless virus, but in selenium deficient individuals it transforms into something deadly. Having adequate levels of selenium stops viruses in our body from becoming more harmful, making it easier for our immune system to eliminate them.
Figure 3. Coxsackievirus infection in people with adequate levels of selenium is pretty harmless: the worst it can give you is a fever. However, the story is very different in selenium deficient individuals. Lack of selenium causes oxidative stress which leads to viral mutations. These genetic alterations are responsible for turning harmless coxsackievirus into a deadly virus that causes Keshan Disease.
Beck, M.A., Levander, O.A. & Handy, J. (2003). Selenium deficiency and viral infection. The Journal of Nutrition, 133, 1463-1467.
Beck, M.A., Nelson, H.K., Shi, Q., Van Dael, P., Schiffrin, E.J., Blum, S., Barclay, D. & Levander, O.A. (2001). Selenium deficiency increases the pathology of an influenza virus infection. The FASEB Journal, 15(8), 1481-3.
Chen, X., Yang, G., Chen, J., Chen, X., Wen, Z. & Ge, K. (1980). Studies on the relations of selenium and Keshan Disease. Biological Trace Element Research, 2(2), 91-107.