When I fell ill with COVID-19 for six weeks this spring, I began eating seafood almost every day. I happened to have large bags of shrimp and scallops in my freezer, and dinner became a few pieces cooked in my microwave in a glass bowl with garlic, ginger, soy sauce, peapods, mushrooms, and onions. I would stumble out of bed, assemble the ingredients (all pre-chopped), and have my simple, tasty meal within minutes. It was easy, fast, nutritious, and comforting.
Although I didn’t guess at the time, my new habit may have helped me. Shrimp and scallops are rich in many nutrients, including selenium, an essential trace mineral. Research with patients in China and Germany now suggests selenium may play a role in recovery from COVID-19 (Moghaddam et al., 2020) (Zhang et al., 2020). In fact, measuring your selenium levels eventually may help doctors predict your risk of a serious case if you do fall ill (Moghaddam et al., 2020).
The coronavirus aside, if you have symptoms of selenium deficiency, including infertility or fatigue, hair loss, mental fog, muscle weakness, or a tendency to colds and viruses, it’s worth checking your levels and vital to up your selenium intake if needed. For most adults, roughly five ounces of wild-caught salmon will meet your daily requirement.
What is selenium?
For almost 150 years, selenium was considered a poison for humans and livestock. Its reputation changed in the late 1950s. By the 1980s, scientists had discovered selenocysteine, the 21st amino acid and the only one containing selenium. It is the building block of a family of proteins called selenoproteins. Any changes in the synthesis of these proteins can affect nearly all of our body tissues (Avery and Hoffman, 2018), which is probably why a lack of selenium is associated with an increased risk of a wide range of conditions.
Selenium is so important to the brain and endocrine system that our bodies have evolved ways to maintain normal concentrations for key functions even when there is too little in our diet. We need selenium for many purposes, and one of the most important may be for optimal immunity.
Brazil nuts, seafood, and organ meats are the foods richest in selenium. Other good sources are beef grazed on selenium-rich grasses and foods made from grains grown in selenium-rich soils.
Rain, evaporation, pesticides, and pH levels may all alter selenium levels in soil. Because the soil and food in regions of China, New Zealand, Europe, and Russia have low levels of this vital nutrient, illnesses related to deficiencies are more common there. Most American adults seem to meet the U.S. recommended dietary allowance for selenium, 55 micrograms a day. However, there are reasons your body may not use it optimally; for example, if you have Crohn’s disease.
How selenium affects recovery from COVID-19
The science linking selenium and immunity has been evolving for decades. Studies using cells in test-tubes, as well as on rodents, livestock, and humans, have shown that adequate selenium, and its efficient incorporation into certain selenoproteins, affects immunity.
In April, an international team reported that people in parts of China with higher selenium levels had recovered more quickly from COVID-19. The team chose data from February 18, 2020, as a snapshot of the progress of the outbreak to that date. The recovery rate in Enshi, a city in Hubei Province, was much higher, at 36 percent, than that of other Hubei cities, where the overall rate was 13 percent. (Don’t worry, this does not mean that 87 percent died, but rather that percentage was still sick as of that date.)
Scientists already knew Enshi citizens enjoyed lots of selenium in their diet, so much so that selenium toxicity was observed there in the 1960s. On the other hand, in Heilongjiang Province in northeast China, a notoriously low-selenium region, death rates were higher than elsewhere in China. This part of China includes the city of Keshan, where historically low selenium levels in the soil made people vulnerable to a particular strain of virus that weakened the heart (Zhang et al., 2020). Keshan disease peaked in the 1960s, killing thousands.
In July, a German team reported that blood samples from 33 COVID-19 patients in Aschaffenburg-Alzenau, Germany, showed they were more likely to be short of selenium than Europeans in general. Among those that died, from 65 to 70 percent showed a deficiency, depending on the measurement used, compared to around a third of the survivors. The team also found the selenium levels improved as patients recovered and declined in those who died (Moghaddam et al., 2020).
Can supplements or eating more selenium-rich food help lower the risk of severe symptoms from COVID-19?
Perhaps. Supplements have helped with other respiratory illnesses. Selenium supplements modulated the inflammatory response in respiratory distress syndrome patients in helpful ways (Mahmoodpoor et al.,2018). In mice with allergic asthma, selenium supplements calmed down the inflammation of airwaves, taming an immune overreaction.
As with most supplements, taking extra selenium is most helpful when it boosts your levels so you are no longer deficient. In general, taking in more selenium stimulates the immune system. So for example, when people with low selenium levels received a supplement, their response to a polio vaccine improved (Broome et al., 2004). Selenium-enriched foods activate white blood cells that fight invaders.
Just be aware: it’s possible to take too much selenium and you may not need it. The safe upper limit is 400 micrograms a day.
COVID-19 patients who are sick a long time as I was, or have other illnesses, are at higher risk for a deficiency and might benefit from an extra-selenium-rich diet or supplements (Moghaddam et al.,2020). I’ll never know for certain if my shrimp and scallop regime sped my recovery, but it’s possible, and it certainly tasted great!
Avery J, Hoffman P. Selenium, Selenoproteins, and Immunity. Nutrients. https://pubmed.ncbi.nlm.nih.gov/30200430/. Published September 1, 2018.
Broome CS, McArdle F, Kyle JA, et al. An increase in selenium intake improves immune function and poliovirus handling in adults with marginal selenium status. Am J Clin Nutr. https://pubmed.ncbi.nlm.nih.gov/15213043/ Published July, 2004.
Mahmoodpoor A, Hamishehkar H, Shadvar K, et al. The Effect of Intravenous Selenium on Oxidative Stress in Critically Ill Patients with Acute Respiratory Distress Syndrome. Immunol Invest. https://pubmed.ncbi.nlm.nih.gov/30001171/ E-published July 12, 2018
Moghaddam A, Heller RA, Sun Q, et al. Selenium Deficiency Is Associated with Mortality Risk from COVID-19. MDPI. https://www.mdpi.com/2072-6643/12/7/2098/htm. Published July 16, 2020.
Office of Dietary Supplements - Selenium. NIH Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/. Accessed August 22, 2020.
Rayman MP. The importance of selenium to human health. Lancet (London, England). https://pubmed.ncbi.nlm.nih.gov/10963212/. Published July 15, 2000.
Zhang J, Taylor EW, Bennett K, Saad R, Rayman MP. Association between regional selenium status and reported outcome of COVID-19 cases in China. OUP Academic. https://academic.oup.com/ajcn/article/111/6/1297/5826147. Published April 28, 2020.