- but researchers warn against reduced intake levels
Even if you eat a healthy and balanced diet, it can be difficult to get enough selenium because of climate changes and nutrient depletion of the soil, especially in Europe. This was shown in a study conducted by Swiss scientists. Selenium is very important for the immune system, but how much do we need to be optimally protected against infections? There also appears to be a connection between widespread selenium deficiency and the increased rate of cancer.
The selenium content in our food depends on how much selenium there is in the soil. Farming methods and climate change, however, could result in additional loss of selenium from as much as 66% of the world’s cultivated areas. The problem appears to affect Europe in particular
The calculations are based on a larger number of soil samples, which have been analyzed by scientists from Swiss Federal Institute of Aquatic Science and Technology. They suggest that selenium deficiency is becoming increasingly widespread, and this has a negative impact on the different proteins and white blood cells of the immune system.
Selenium is removed from the soil in the following ways:
A selenium deficiency weakens the immune defense. Farmers already use supplements
Selenium is necessary for normal functioning of around 30 different selenium-dependent enzymes (selenoproteins) that control the energy turnover, immune defense, cancer prevention, and a number of other essential body functions.
Numerous studies carried out on humans and animals have shown that a selenium deficiency impairs the immune system’s ability to fight virus, tumors, and allergens. Since the early 1970s, farmers have given extra selenium to their animals to avoid deficiency diseases. Although we humans are a part of the same food chain, there still are no official guidelines for how much selenium we should take to saturate the different selenoproteins.
Selenium is important for the immune defense
Selenoproteins function as enzymes that influence the different proteins and white blood cells of the immune system. First of all, selenoproteins are important for our non-specific (innate) immune defense, which handles the majority of infections. Secondly, selenoproteins are important for the specific (adaptive) immune system that develops after birth, and which is able to specialize, produce antibodies, and make us immune. Finally, several selenoproteins function like antioxidants that protect the healthy cells against immune attacks.
As soon as we get an infection, white blood cells from our non-specific immune system absorb enormous amounts of oxygen and convert it into free radicals. These free radicals serve as destructive missiles against intruding microorganisms. The process is called “respiratory burst”.
During the process, white blood cells take up a lot of selenium and vitamin C to help them carry out frontal attacks. That way, this part of our immune system, which can be compared to storm troops, can fight a developing infection before we ever find out.
However, the free radicals are very aggressive molecules that may also cause chain reactions and cellular damage, unless they are harnessed. We therefore need protective antioxidants to limit the detrimental effect of free radicals, and selenium, vitamin C and certain other compounds play a role in this connection.
|If the body has enough selenium and other nutrients, the immune defense can normally nip an infection in the bud without us feeling a thing.|
Selenium activates T cells from the non-specific immune defense
In situations where the white blood cells from our non-specific (innate) immune system fall short, they message the T cells. They then divide into an entire army, which can direct attacks against the intruding microbes. This mobilization normally takes a week, and it is during this period that we feel ill.
Scientists have found that in the late stages of an influenza infection, levels of macrophages, T helper cells (CD4 cells) and cytotoxic T cells (CD 8 cells) are lower in selenium-deficient mice compared with mice who have plenty of selenium. Interestingly, there was no major difference among levels of influenza antibodies in the two groups. The researchers therefore assume that selenium is more important for our T cells than for the B cells that produce antibodies.
An American study has shown that supplementing with 200 micrograms of selenium daily increases cytotoxic T cell activity by 118% and NK cell (Natural Killer) activity by 82%. This increase gives an improved protection against infections and cancer.
Selenium prevents flu, cold, and herpes virus from mutating
The reason why so many of us are affected by repetitive infections (colds, flus, and herpes), is that these virus types are so-called RNA viruses and are very good at mutating. RNA virus may change its appearance or its antigens, thereby deceiving the immune defense and preventing it from developing immunity. The immune system therefore has to start over every time, especially if it is compromised, in the first place. This is where selenium fits into the picture.
Melinda A. Beck, a professor from the University of North Carolina, United States, has revealed that selenium-deficient mice infected with influenza virus A have an increased rate of RNA virus mutations. These mice also have difficulty with fighting the flu compared with mice who have plenty of selenium in the body. The influenza-infected mice that lacked selenium developed serious lung complication due to their influenza, whereas the mice that had plenty of selenium only suffered mild symptoms
|Selenium is important for preventing the mutation of influenza virus and other RNA virus types. It is no coincidence that new, dangerous influenza strains often originate from selenium-depleted regions of China, Central Africa, and Southeast Asia.|
Life-threatening virus and selenium deficiency
In the Keshan province of the Northeastern part of China where the selenium content in the soil is extremely low, a lethal heart disease (Keshan disease) was discovered. It was caused by the Coxsackie virus, a normally harmless RNA virus, which the immune system is unable to fight when the body lacks selenium. In 1965, the population in that area started using selenium supplements to prevent and eradicate the feared disease.
In the meantime, many studies have shown that selenium has a specific ability to prevent different virus infections, given that we have enough of the nutrient in the body to saturate all the different selenoproteins.
Less selenium means higher AIDS mortality
In HIV-infected individuals with low blood selenium levels, there are fewer T helper cells, AIDS develops faster, and they have higher mortality. Researchers have also observed that in areas with low selenium levels in the soil, the AIDS mortality rate is higher. This was demonstrated in an American study that compared the two variables in different states. It turns out that blood levels of selenium drop long before the HIV-infected patients start to feel sick. It is like a ticking bomb that is likely to produce a ten-fold increase in their risk of dying of AIDS, partly because of a poorly performing immune system, partly because there is too little selenium for other essential body functions. The higher the selenium content in the blood, on the other hand, the greater the chances of surviving in spite of the disease.
Selenium’s effect on the Candida fungus and other microorganisms
The majority of studies focus on selenium’s role in preventing and treating virus infections. The nutrient’s effect on bacteria and fungi is not as thoroughly documented. Nonetheless, a mouse study shows that selenium deficiency increases ones susceptibility to Candida albicans infections. This fungus is a natural part of our natural microflora, but in situations with overgrowth, symptoms like thrush, white discharge, digestive problems, and anal itching may occur.
Danish researchers show that selenium inhibits inflammation
When the immune system has defeated an infection or repaired cellular damage of some kind, it needs to stand down to avoid chronic inflammation. Although chronic inflammation goes unnoticed, it involves a constant free radical bombardment of the body, which can be detrimental. Lifestyle-associated conditions such as metabolic syndrome, type 2 diabetes, and cancer are all characterized by chronic inflammation. The same is the case with auto-immune diseases like rheumatoid arthritis, sclerosis, type 1 diabetes, Crohn’s disease, and metabolic disorders like Hashimoto’s disease and Graves disease. We have in our body some pro-inflammatory compounds called interleukin-6, and it turns out that they increase when there is a selenium deficiency. It also turns out that the selenium-containing GPX proteins inhibit interleukin-6 and therefore have an anti-inflammatory effect. This was seen in a Danish study from Århus University where selenium supplements stimulated the GPX activity in patients with rheumatism.
Selenium’s role in the immune system
Selenium yeast prevents cancer
Several studies conducted in the past decades have pointed to selenium’s cancer-inhibiting role. For instance, an American researcher named Larry Clark published the so-called NPC study (Nutritional Prevention of Cancer), in which he demonstrated that 200 micrograms of selenium yeast daily could reduce cancer mortality by 50%. Millions of people could avoid or survive cancer simply by getting more selenium.
Another study that is often referred to is the subsequent SELECT trial, where scientists failed to demonstrate a similar effect of selenium (and vitamin E). They used a different selenium source (selenomethionine), but selenium yeast contains a variety of organic selenium species and is therefore a much better source.
Selenium decrease advances the cancer disease
It is possible to detect a decrease in blood selenium levels in cancer patients long before their disease is diagnosed. Because cancer takes many years to develop, selenium is therefore a vital element in the long-term prevention of cancer.
Selenium’s six anti-cancer mechanisms
Selenium supports the ageing immune system
Ageing is a complicated process that involves free radicals and changes in the metabolism, hormone system, and immune system. A study of healthy, older (57-84 years) people showed improvements in those who got daily supplements of beta-carotene (45 mg) and/or selenium (400 micrograms) for six months. The selenium supplement alone accounted for an increase in T helper cells (CD4 cells) of more than 50%. This increase continued two months after they discontinued their supplementation.
Selenium also serves as a very important antioxidant that protects the cells. Many studies have shown that selenium helps ageing people to maintain a well-functioning immune defense and good health in general.
Selenium sources and supplements
We get selenium from fish, shellfish, organ meat, eggs, dairy products, and Brazil nuts (a particularly good source). Danish crops are generally low in selenium, and it even appears to be a problem to get enough selenium even if you eat fish and shellfish five times a week.
Most human selenium studies are conducted with doses of around 100-200 micrograms/day, which is two to four times more than what the average European diet provides.
It takes 100 micrograms of selenium daily to saturate a very important selenoprotein
Selenoprotein P, very important selenium-containing protein, is used as a marker for blood selenium levels. Studies show that you need around 100 micrograms of selenium each day to effectively saturate this selenoprotein.
Overview of the immune defense
|Defense||Non-specific (innate)||Specific (adaptive)|
|Functions as||Storm troops, messengers, and “garbage collectors”||Special troops that develop immunity.
Develops after birth
|Mechanical and biological||Skin and mucosa.
|Specific compounds in the ”acute” phase||Interferons
|Direct cell destruction||Dendrite cells
|T cells. Responsible for virus, fungus, and cancer cells.
B cells and antibodies. Especially responsible for bacteria and toxins
Jones GD et al. Selenium deficiency risk predicted to increase under future climate change. Proceedings of the National Academy of Sciences 2017
Editorial team. Selenium deficiency promoted by climate change. ETHzüric 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. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3723386/
Hagemann-Jensen Michael et al. The Selenium Metabolite Methylselenol Regulates the Expression of Ligands That Trigger Immune Activation through the Lymphocyte Receptor NKG2D. The Journal of Biological Chemistry. 2014.
Klein EA et al. Vitamin E and the risk of prostate cancer: The Selenium and Vitamin E Cancer Prevention Trial (SELECT). Jama 2011.
Bleys J et al: Serum selenium levels and all-case cancer, and cardiovascular mortality among US adults. Arch Intern Med. 2008.
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.
Clark LC et al: Effects of Selenium Supplementation for Cancer Prevention in Patients with Carcinoma of the Skin. Journal of the American Medical Association: 1996.
Pernille Lund. Immunforsvarets nye ABC. Hovedland. 2012
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