Are you getting enough selenium for your immune defense, gut flora, and cancer prevention?
The widespread selenium deficiency in Europe increases the risk of infections, inflammatory bowel disorders, and abnormal cell development. In a new review article published in Nutrients, the authors look at selenium’s role in the highly developed immune defense. This includes the immune defense’s communication, which is vital for our ability to fight off viruses and germs swiftly and directly, and for avoiding unwanted inflammation that can become potentially life-threatening. Selenium also serves as a very effective antioxidant that protects cells and their DNA against oxidative damage. In addition, selenium has a number of anti-cancer mechanisms.
The immune defense needs most vitamins and minerals. In recent years, more and more attention has been directed towards selenium, which is because there is widespread selenium deficiency, even among those who eat an otherwise healthy and balanced diet. Selenium is found in the soil. Plants absorb the nutrient and pass it on to animals and humans. There are regions in the world (such as Europe) where the selenium content in the agricultural soil is low. This is why more than one billion people worldwide lack selenium, which supports a long list of essential proteins and enzymes that are important for our health. Selenium is also a vital part of some powerful antioxidants that protect cells and their DNA against damage caused by oxidative stress. This is when harmful free radicals outnumber the protective antioxidants. All people generate free radicals as a natural part of their oxygen turnover. The free radical load, however, is increased tremendously by things such as ageing, infections, chronic inflammation, smoking, and poisoning. In their review article, the authors look closer at selenium’s role in the immune defense (both the innate defense and the adaptive immune defense), in virus infections, bacterial infections, yeast infections, autoimmune diseases, cancer, and the gut flora.
The innate immune defense
The innate immune defense is designed to react swiftly to various pathogens and cell damage. It includes the complement system and various white blood cells such as mast cells, NK cells (Natural Killer cells), monocytes, macrophages, dendritic cells, and different granulocytes.
During infections, blood levels of selenium are drastically reduced because the white blood cells need selenium to function. One of the immune system’s first reactions to pathogens is something called respiratory burst, where the immune defense’s monocytes, macrophages, and granulocytes attack pathogens using free radicals as their weapon. The process is controlled by selenoprotein K, among others. Meanwhile, the selenium-containing antioxidant GPX (glutathione peroxidase) makes sure that the free radical attack is limited to pathogens to prevent unwanted damage to cells and tissues.
Selenium is also important for enabling monocytes, macrophages, and granulocytes to carry out phagocytosis, which is a process in which they devour and destroy pathogens.
The white blood cells also need selenium to help them communicate, differentiate, and initiate targeted inflammatory attacks. Selenium’s anti-inflammatory effect is linked to the fact that macrophages need selenium to shift from being pro-inflammatory to anti-inflammatory. Selenium also helps the immune defense in its communication with the adaptive immune system when there is a need for assistance and for making antibodies. If the body lacks selenium, it increases the risk of infections and unwanted inflammation. The innate immune defense tends to become weaker with age, and being selenium-deficient contributes to the problem.
The adaptive immune defense
The adaptive immune defense develops after birth and as a result of contact with foreign substances and pathogens. It primarily consists of T cells, B cells, and antibodies. T cells are responsible for fighting virus infections, yeast infections, and abnormal cells. B cells help fight off bacterial infections, they protect against toxins, and they are needed for antibody production.
It is especially macrophages from the innate immune defense that call for assistance from the adaptive immune defense when necessary. T cells also need selenium to make different cytokines, to differentiate, and to attack. Selenoprotein K in particular seems to play a vital role. Studies of animals and humans have shown that selenium supplementation has a positive impact on the adaptive immune system.
Virus infections
Selenium has a particular potential when it comes to fighting virus infections because of its role in both the innate and adaptive immune defenses. As mentioned earlier, selenoprotein K is very important. Selenium also serves as a powerful antioxidant.
In connection with virus infections like influenza, herpes, hepatitis, HIV, and Epstein-Barr virus, the formation of free radicals or reactive oxygen species (ROS) increases heavily. If the free radical burden is too overwhelming, it may cause RNA viruses to mutate, making them even more harmful. Selenium prevents this from happening.
COVID-19 infections and influenza do not become potentially life-threatening unless there is cytokine storm and hyperinflammation. COVID-19 patients with severe acute respiratory syndrome (SARS) have lower selenium levels in their blood compared with healthy people, which reflects the increased need for selenium combined with an increased selenium excretion in connection with the infection.
Selenium supplements generally seem to boost the immune defense and help it fight off virus, while preventing serious complications and speeding up recovery.
Bacterial infections
Selenium deficiency is often seen in connection with bacterial infections, which is why selenium supplements are given to animals infected with E Coli, Clostridium perfringens, and other kinds of bacteria. Tuberculosis can also be caused by selenium deficiency. On the other hand, when tuberculosis patients are treated with selenium, it speeds up their recovery by strengthening the immune defense and counteracting unwanted inflammation.
In their review article, the authors mention studies where selenium has been shown to have a positive effect on the body’s ability to fight off yellow staphylococcus (staphylococcus aureus). This is helpful because of the problems with antibiotic resistance.
Systemic infections can also cause blood poisoning (sepsis), which is a huge and overlooked global health problem with a death toll of millions. Sepsis occurs as a result of an overreactive immune defense, which causes hyperinflammation and oxidative stress. Studies suggest that selenium supplementation may have a positive effect on certain sepsis parameters.
- When COVID-19, influenza, and sepsis become life-threatening, it is because of an unhinged immune defense that reacts with cytokine storm and hyperinflammation.
- Lack of selenium and other nutrients increases the risk of an uncontrolled immune reaction.
Yeast infections
Although yeast and fungi are part of the natural microflora, they can also cause disease if they spread and release different mycotoxins. Pathogenic fungi are found naturally in our environment. Studies suggest that selenium protects against yeast types like Candida albicans and Aspergillus Niger. Besides strengthening the body’s own immune defense, the selenoproteins are able to help destroy the cell walls of the yeast cells, to inactivate their enzymes, and to reduce their ATP synthesis. There is a growing problem with yeast becoming resistant to anti-fungal drugs, but selenium represents a promising new therapy choice.
Autoimmune diseases
Autoimmune diseases make the immune defense attack the body’s own tissues and cause damage. Selenium deficiency is especially known to contribute to autoimmune thyroid disorders such as Hashimoto’s disease that causes hypothyroidism and Graves’ disease that causes hyperthyroidism. In relation to its weight, the thyroid gland contains more selenium than any other organ in the body. Selenium supports a host of selenium-dependent enzymes and antioxidants that control the thyroid hormones and protect cells against oxidative stress. Studies have shown that daily supplementation with 200 micrograms of selenium yeast for 3-6 months has a positive effect on patients suffering from autoimmune thyroid disorders. In Hashimoto’s patients, selenium has been seen to regulate T cell activity and lower the amount of anti-TPO antibodies.
Selenium is also important for the gut flora and the intestinal immune defense. In fact, it appears that selenium deficiency can increase the risk of inflammatory bowel diseases such as Crohn’s disease and ulcerative colitis.
In a placebo-controlled, randomized study, patients with ulcerative colitis were given 200 micrograms of selenium daily for 10 weeks. The treatment had a positive effect on several disease parameters and improved the patients’ quality of life. There seems to be a lot of evidence that selenium has a potential when used as part of the treatment for different inflammatory bowel diseases.
Cancer
Selenium’s has various functions in the immune defense, including destroying abnormal cells such as cancer cells. Selenium must be able to activate NK cells and T cells, so they attack directly. Selenium also regulates the inflammatory processes that lead to the death of cancer cells. In addition, selenium regulates ferroptosis and other processes that play a critical role in cancer. As a powerful antioxidant, selenium protects cells and their DNA against free radical damage and oxidative stress.
The American professor, Larry Clark, conducted the NPC study (Nutritional Prevention of Cancer), which is the first placebo-controlled study to show that daily supplementation with 200 micrograms of selenium yeast can prevent three of the most common cancer forms and lower cancer mortality by around 50 percent. A subsequent study called SELECT (Selenium and Vitamin E Cancer Prevention Trial), however, failed to show a similar effect of giving selenomethionine and synthetic vitamin E. The conflicting results of these two studies may be a result of using different forms of selenium. Also, if the study participants were not selenium-deficient to begin with, they may not have responded to the supplements.
Still, there seems to be a link between the widespread problems with selenium deficiency and an increased risk of developing different types of cancer. It also appears that high-dosed supplements of selenium yeast that optimize blood levels of the nutrient can improve the treatment and rehabilitation of cancer patients. It normally takes many years for cancer to develop, so it is always a good idea to make sure to have plenty of selenium in the blood.
The gut flora
The human gut flora harbors billions of bacteria that help us absorb nutrients, displace harmful microorganisms, and synthesize vitamins, enzymes, neurotransmitters, and other compounds that are important for us. It is essential to maintain the proper balance or equilibrium between the different microorganisms. This is known as symbiosis. If the symbiosis is disrupted because of unhealthy diet habits, antibiotics, painkillers, and other disturbing factors, it can result in dysbioses that cause potentially harmful species to spread and become dominating. This can lead to autoinfections such as pneumonia. Other things like poor digestion, inflammatory bowel diseases (IBD) and other disorders may also occur. Selenium offers important support for a number of beneficial microorganisms in the gut flora. It also helps the intestinal immune defense break down pathogens and toxins from the food. Selenium even has an anti-inflammatory effect.
Being selenium-deficient generally seems to have a negative impact on the healthy gut flora. This increases the risk of inflammatory bowel disorders like Crohn’s disease and ulcerous colitis as well as intestinal cancer and other ailments.
Selenium sources, requirements, and supplementation
There is selenium in fish, meat, offal, eggs, dairy products, Brazil nuts, wholegrains and a number of other things. The selenium content in food depends on how much selenium is in the soil, and in our part of the world it is difficult to get enough selenium from the diet. According to the updated Nordic Nutrient Recommendations, women should get at least 75 micrograms each day, while men should aim for 90 micrograms. Doses of up to 200 micrograms daily have been used in studies with good results, and selenium yeast with many different selenium compounds have have the best effect. The European Food Safety Authority (EFSA) has set a safe upper intake level of 300 micrograms daily.
References:
Lutz Schomburg. The Immunomodulatory Effects of Selenium: A Journey from the Environment to the Human System. Nutrients 2024
Christina Pfister, Joerg Schoenemann. Selenium in Cancer Rehabilitation – A Retrospective Study from a Specialized Clinic. Nutrients 2023 Sep.
Nordic Council of Ministers. Nordic Nutrition Recommendations 2023
Clark LC et al: Effects of Selenium Supplementation for Cancer Prevention in Patients with Carcinoma of the Skin. JAMA: 1997.
Nordic Council of Ministers. Nordic Nutrition Recommendations 2023
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