Selenium may be one of the most under-appreciated immune factors in the human body. When there’s talk about supporting the immune system, vitamin C, vitamin D, zinc, and a host of other vitamins, minerals and herbs get listed. Selenium rarely does, despite its essential role in immune response.
In this article, selenium will get the attention it deserves as we look at:
- What selenium is
- Why it’s important to the immune system
- Symptoms of selenium deficiency
- Good sources of dietary selenium
What is Selenium?
Selenium is a mineral, but for humans, it’s much more than that. For people, selenium is an essential micronutrient required for DNA synthesis, fertility, production of thyroid hormones and the immune system. As part of the amino acid selenocysteine, it is considered the 21st amino acid for its role in proteins that regulate inflammation.
Why Selenium is Important to the Immune System
A small 2004 British study illustrates selenium’s importance to the immune system.[i]
In the study, researchers took 22 healthy adults with low selenium levels. For 15-weeks some received selenium while the others got a placebo. After 6 weeks, all participants received a polio vaccine. Those who took the selenium supplements:
- Had an increased cellular immune response
- Cleared the vaccine from the blood faster
- Experienced a faster T-cell response
- Produced more T helper cells and cytokines
In short, selenium is essential to the body’s response to viral infection, a conclusion supported by extensive research.[ii]
Selenium is also an essential component in glutathione peroxidase, one of the body’s top antioxidants. As part of the selenoproteins (made from the amino acid selenocysteine), it plays a role in the body’s detoxification – regulation of immune response to prevent a hyper-response that would result in an autoimmune response or chronic inflammation, and immune cell production.[iii]
Another area currently being studied involves relationship between irritable bowel disease (IBD) and selenium. It’s been thought inflamed bowels like those of IBD and Crohn’s disease may prevent absorption of selenium. Research suggests boosting selenium levels may help ease the condition, however. Although the relationship is not well understood yet, it is known that individuals who suffer from digestive conditions like these do tend to have low levels of selenium.[iv]
Symptoms of Selenium Deficiency
In the U.S., it is presumed that most people are not selenium deficient. Of course, there isn’t a good test for it, making it hard to diagnose the condition. If it’s suspected, doctors will often test glutathione peroxidase levels as this essential antioxidant cannot be produced without selenium.
Today, with soil depletion and diets lacking nutrients, there’s a growing thought that selenium deficiency may be a reason behind many health problems and weakened immune systems. The British study noted above shows it’s possible to be considered medically healthy and still have low levels of selenium. Common symptoms don’t make it any easier to diagnose. They include:
- Frequent sickness
- Brain fog
- Muscle weakness
- Hair Loss
Now, it’s important to note that some research suggests too much selenium might increase the risk of diabetes.[v] So it’s important not to get too much selenium. The best answer to prevent selenium deficiency and ensure a strong immune system is by including selenium-rich foods in the diet when possible.
Dietary Sources of Selenium
Eating fresh, organic foods should provide ample amounts of selenium in the diet and keep your immune system in top shape to fight viruses and detox the body.
Foods high in selenium include fish, lean meats and nuts, especially brazil nuts. Here’s a list of the top selenium-rich foods, courtesy of the USDA.[vi]
|Brazil nuts, 1 ounce (6–8 nuts)||544||777|
|Tuna, yellowfin, cooked, dry heat, 3 ounces||92||131|
|Halibut, cooked, dry heat, 3 ounces||47||67|
|Sardines, canned in oil, drained solids with bone, 3 ounces||45||64|
|Ham, roasted, 3 ounces||42||60|
|Shrimp, canned, 3 ounces||40||57|
|Macaroni, enriched, cooked, 1 cup||37||53|
|Beefsteak, bottom round, roasted, 3 ounces||33||47|
|Turkey, boneless, roasted, 3 ounces||31||44|
|Beef liver, pan-fried, 3 ounces||28||40|
|Chicken, light meat, roasted, 3 ounces||22||31|
|Cottage cheese, 1% milkfat, 1 cup||20||29|
[i] Caroline S Broome, Francis McArdle, Janet AM Kyle, Francis Andrews, Nicola M Lowe, C Anthony Hart, John R Arthur, Malcolm J Jackson; An increase in selenium intake improves immune function and poliovirus handling in adults with marginal selenium status, The American Journal of Clinical Nutrition, Volume 80, Issue 1, 1 July 2004, Pages 154–162, https://doi.org/10.1093/ajcn/80.1.154
[iii] Huang Z, Rose AH, Hoffmann PR. The Role of Selenium in Inflammation and Immunity: From Molecular Mechanisms to Therapeutic Opportunities. Antioxidants & Redox Signaling. 2012;16(7):705-743. doi:10.1089/ars.2011.4145.