Lack of selenium increases your risk of viral infections
– and could even make them more dangerous
Selenium is of vital importance to a strong immune defense. Still, selenium deficiency is a common problem and it increases the risk of viral infections such as influenza and the coronavirus from China, which is feared to turn into a global pandemic. It is a problem that selenium deficiency in infected animals and humans causes the virus to mutate and become more aggressive. Because of selenium’s important role as a powerful antioxidant, being deficient of this micronutrient may leave the body vulnerable to oxidative stress, which can cause tissue damage and complicate the virus infection. It is therefore important to get enough selenium at all times, as it also increases our resistance towards other viral infections such as herpes, HIV, and hepatitis, according to an article published in Nutrients.
Through history, dangerous viruses have killed more people than any war or natural catastrophe. More than 500 million people worldwide contracted the highly virulent influenza known as the Spanish Disease, which ran rampant during the period 1918-1920. An estimated 20-50 million lives were lost. Millions of people have also succumbed to AIDS, hepatitis, and Ebola virus. Now, there is widespread concern over the new coronavirus that was originally identified in China but has spread to all the other continents.
It goes without saying that proper hand hygiene should always be first priority to prevent such viruses from spreading, but nutrition also plays a vital role. Decades of research have shown that being deficient of certain micronutrients makes us more vulnerable to contamination, and the infections also become increasingly complicated.
|Around one billion people worldwide are believed to lack selenium, primarily due to nutrient-depleted farmland. The soil in Europe, large parts of China, India, South America, South Africa, and the south-west part of the United States is low in selenium.|
The immune defense requires plenty of selenium – especially during infections
Selenium supports around 25 different selenium-dependent enzymes known as selenoproteins, which help control our energy turnover, immune defense, and a host of other important functions. Selenoproteins are vital for the non-specific, innate immune defense, which serves as storm troops and silently fights off germs in the background. But selenoproteins are also important for the specific, adaptive immune defense that develops after we are born and has the ability to specialize, produce antibodies, and create immunity. An American study showed that daily supplementation with 200 micrograms of selenium increased (by 118 percent) the activity of T killer cells, a type of white blood cells. Also, natural killer (NK) cell activity was increased by 82 percent. Such increases provide improved protection against infections.
Finally, many selenoproteins serve as antioxidants that protect healthy cells when the immune defense attacks.
Selenium prevents viral infections from producing harmful oxidative stress
Free radicals are both essential and dangerous. Free radicals are highly aggressive oxygen molecules with an unpaired electron that snatch electrons from other molecules – for better or for worse. They are also referred to as reactive oxygen species (ROS) and play an important role in several physiological functions such as cell signaling and programmed self-destruction of cells (apoptosis). ROS are also natural byproducts of the cellular energy turnover that takes place inside the mitochondria.
When the body contracts a viral infection the white blood cells of the immune defense release cascades of ROS in the form of hydrogen peroxide and super oxide. They work like missiles when the body is attacked by virus and other microorganisms. The production of pro-inflammatory cytokines also generates large amounts of ROS.
What is important here is to make sure that the ROS are kept on a tight leash so these aggressive free radicals only carry out specifically assigned tasks without causing cellular damage or oxidative stress. Oxidative stress is an imbalance between ROS and the cellular antioxidant defense mechanisms where the ROS run rampant, starting destructive chain reactions inside and outside the cells. The lipids in the cell membranes together with the DNA and proteins inside cells are sitting ducks for ROS activity, and this also goes for essential cholesterol that floats in the bloodstream.
The ROS impact is increased by the ageing process and environmental factors such as smoking, heavy metal exposure, medicine consumption, UV radiation from the sun, and electromagnetic radiation. Oxidative stress sets the stage for cellular damage and several chronic ailments such as atherosclerosis, diabetes, and cancer. Therefore, it is vital that our defense mechanisms are able to fight infection swiftly and effectively.
It is documented that ROS levels increase drastically and cause oxidative stress in connection with infections caused by influenza virus, Epstein Barr virus (mononucleosis), HIV, hepatitis B and C, and other types of virus. Oxidative stress can even complicate the viral infections. Therefore, when the body contracts a viral infection, it has an immediate need for protective antioxidants like selenium. Studies show that selenium is vital for the powerful GPX (glutathione peroxidase) antioxidants that are particularly important for neutralizing hydrogen peroxide and organic hydroperoxide (two specific kinds of ROS) before they are able to cause oxidative damage.
The first discovery of life-threatening virus in China caused by selenium deficiency
In the Northeastern Keshan Province of China where the soil is extremely low in selenium, scientists discovered a potentially lethal heart disease that they dubbed Keshan Disease. It is caused by a normally harmless RNA virus named Coxsackie, which the immune disease is unable to fight without the presence of selenium. As early as in 1965, the Chinese in Keshan started preventing and eradicating the dreaded disease with help from selenium supplements.
Keshan disease is the consequence of extreme selenium deficiency, but even minor deficiencies can impair the immune system. Numerous studies have demonstrated that selenium has a particular ability to prevent different viral infections, provided we get enough of the nutrient to saturate the selenoproteins.
Coronavirus – from harmless to life-threatening
Coronavirus is a large family of RNA viruses found in birds and animals. Coronavirus is known to cause a large percentage of normal colds in human adults. One type of Coronavirus is the cause of SARS (Severe Acute Respiratory Syndrome), which had its origin in China in 2002 and has taken more than 800 lives. The new strain of Coronavirus, 2019-nCoV, was discovered in the Chinese Wuhan metropolis in December of 2019. It originally came from bats or snakes, and its epicenter is believed to be a food market in Wuhan. But there are other theories.
The new Coronavirus strain attacks the lower respiratory tract and can cause bronchitis and pneumonia combined with fever. Most episodes of infection have been mild, but in around 20-25 percent of cases people get seriously ill, especially if they are immunocompromised, to begin with. The death toll is on the rise and the virus has spread to several other countries in the Far East, in Europe, the United States, Canada, and Australia.
Science is working around the clock to develop a vaccine but it takes time. In any case, it is essential for the body’s immune defense to get the nutrients it needs because, contrary to vaccines, the immune system is designed to attack any pathogen at any time. Here, it is interesting to look at all the studies that have been made with selenium and other types of RNA virus.
Selenium prevents cold virus, flu virus, and other types of RNA virus from mutating
Many infections cause the body to develop lifelong immunity. The reason why we constantly contract new infections with cold virus, flu virus, and herpes virus is that these virus types, just like the Coxsackie virus and Coronavirus, are RNA viruses that are designed to mutate. The different RNA viruses can change their appearance or their antigens. That way, they can deceive the immune system, making it virtually impossible for the body’s own defense mechanisms to recognize the viruses and combat them. In such cases, the immune system is forced to start all over again.
Professor Melinda A. Beck from the University of North Carolina, Chapel Hill, the US, has demonstrated that selenium-deficient mice, when inoculated with the Coxsackie virus or influenza virus type A, have increased mutations in these types of RNA virus. In other words, their selenium deficiency makes it difficult to fight the viral infections, but this is not the case with mice that have plenty of selenium. The infected mice that lacked selenium developed serious lung complications because of the infections, whereas the mice that did not have a selenium shortage only developed mild symptoms. Selenium is therefore vital for preventing these viral infections from developing or at least ensuring that their duration is short and with few symptoms.
Lower blood selenium equals higher AIDS mortality
There are two types of HIV (Human Immunodeficiency Virus). HIV-1 is the most virulent type and has spread worldwide, whereas HIV-2 is primarily found in West Africa.
HIV attacks several of the immune system’s white blood cells (T cells, monocytes, macrophages, and dendrite cells). The disease can eventually develop into full-blown AIDS (Acquired Immunodeficiency Syndrome), a condition to which millions of lives have already been lost. There is currently no vaccine but it is possible to prevent the virus from being transmitted with help from combination antiretroviral therapy. HIV is also an RNA virus with a unique ability to mutate. Because HIV is chronic it causes oxidative stress and increases the need for selenium and other antioxidants. HIV-infected individuals with low selenium concentrations in their blood have fewer T helper cells, they develop AIDS faster, and have a 20 percent higher risk of dying of their disease compared with those who have higher blood levels of selenium. Scientists have also observed a link between low selenium levels in the soil and increased AIDS mortality in the same regions. This was demonstrated in an American study comparing the two factors across different states.
It also turns out that blood levels of selenium plummet long before the HIV-positive individuals start to feel sick. Being selenium-deficient is a ticking bomb that can multiply HIV-infected peoples’ risk of dying from AIDS. There are several factors involved: The immune system is weak, there is oxidative stress, and there is too little selenium to undertake essential body functions that depend on this nutrient. On the other hand, with higher selenium levels in the blood, the chances of surviving AIDS are far better.
Hepatitis and other types of virus
Today, around three percent of the world’s population, or around 170 million people, are infected with hepatitis C. It attacks liver cells and immune cells. Eighty percent of patients develop chronic liver infection, two percent develop cirrhosis, and one to two percent get cancer of the liver. Many people with HIV also develop hepatitis C. This disease is characterized by oxidative stress in the liver. Science has also found lower concentrations of the selenium-containing GPX antioxidants in patients with hepatitis C compared with healthy controls.
Studies reveal that being selenium- and zinc-deficient increases the risk of the disease becoming chronic and life-threatening. Other studies show that selenium supplementation of hepatitis B patients lowers the risk that their condition develops into liver cancer. Once their supplementation is discontinued, however, their risk of liver cancer is the same as for patients in the control group.
Selenium sources and supplements
Good sources of selenium are fish, shellfish, offal, eggs, dairy products and Brazil nuts. European agricultural crops are generally low in selenium and according to a Danish study that was published several years ago, a diet with lots of seafood is not necessarily a guarantee of getting enough selenium. In this study, people were asked to eat seafood five times per week (a total of one kilo of fish and shellfish weekly). Even with this intake of seafood, blood samples showed that they did not get enough selenium to saturate selenoprotein P, which is very important and used a marker of blood selenium levels. Studies show that it takes around 100 to 125 micrograms of selenium daily to saturate this vital selenoprotein, and that is a lot more than the reference intake (RI) level for selenium.
In the case of infection, the body’s need for selenium increases.
Most human studies of selenium use daily doses of around 100-200 micrograms (1-2 tablets). The best supplements are those with selenium yeast where you get a variety of different selenium species, just like you would get from eating a selenium-rich diet with many different selenium sources.
WHO has established a safe upper intake level for daily selenium intake at 400 micrograms.
Important: Don’t forget vitamin D, vitamin C, and zinc in the battle against virus infections
Virus infections often occur during the winter period, where people tend to lack vitamin D. We also need vitamin C and zinc that strengthen the immune defense and counteract oxidative stress.
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Olivia M. Guillan et al. Selenium, Selenoproteins and Viral Infection. Nutrients 2019
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Proceedings of the National Academy of Sciences 2017
Lutz Shomburg. Dietary Selenium and Human Health. Nutrients 2017
Hoffmann Peter R et al. The influence of selenium on immune responses. Mol Nutr Food Res.
Arthur John R et al. Selenium in the Immune System. The Journal of Nutrition. 2003.
Hertz Niels. Selen et livsvigtigt spormineral. Ny Videnskab 2002
Beck MA, Levander OA. Host nutritional status and its effect on a viral pathogen. J Infect Dis. 2000.
Cowgill U.M. The distribution of selenium and mortality owing to acquired immune deficiency syndrome in the continental Unites States. Biol Trace Elem 1997.
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