The role of zinc and selenium in boosting immune system function by Fahmida Hashem

Almost all nutrients in the diet play a crucial role in maintaining an "optimal" immune response, and both insufficient and excessive intakes can have negative consequences on the immune status and susceptibility to a variety of pathogens.

Zinc is required as an immune response. Physiological supplementation of zinc for 1-2 months restores immune responses, reduces the incidence of infections and prolongs survival. As a constituent of selenoproteins, selenium is needed for the proper functioning of neutrophils, macrophages, NK cells, T lymphocytes and some other immune mechanisms. Selenium appears to be a key nutrient in counteracting the development of virulence and inhibiting HIV progression to AIDS. Our immune system needs certain factors to stay strong and be able fight pathogens. Among the most important ones, as shown by various studies, are Zinc and Selenium.

Zinc is a vital trace mineral for immune system function. The ability of zinc to boost immune system function in certain disorders has been backed up by numerous studies over the past few decades. One particular study conducted by Ohio State University and published on BBC has found that zinc can stop the immune system from getting out of control and causing serious problems after ‘sepsis’ which is a life-threatening condition in which the body attacks its own organs and cells falsely to fight off infection. Zinc in a few lines can either support the function of the immune system when needed or help control its effects when it starts to attack the body’s own cells. This is why it is considered by many as an ‘immune modulator/regulator’.

We have no specialized zinc storage system in our body which means we must take it every day. Zinc is present in a wide variety of foods, but it is important to remember that phytates can bind zinc and inhibit its absorption. Phytates are found in whole-grain bread, cereals, and legumes. This means that zinc contained in grains and plants is not as well absorbed as zinc found in seafood and meat. Vegetarians should note that foods such as garlic and onions may increase the absorption of zinc from plant foods. Examples of foods that are high in zinc oyster, beef, crab, lobstar, fortified cereal, pumpkins seeds, yogurts, cheese, oatmeal, peas. Vegetarians are at higher risk of zinc deficiency because they do not eat meat or seafood. They may require up to 50% more of the RDA to account for reduced zinc absorption because of the presence of phytates. 

So what evidence is there to support taking zinc for COVID-19? There have been hundreds of studies investigating zinc for the common cold. The theory is that zinc could inhibit the binding of the cold virus to cells within the nasal mucosa and suppress inflammation. COVID-19 is a new disease, and we are still learning about it, so to date, there hasn’t been any specific studies of zinc for COVID-19, and we can only look at its effects in other conditions. A Cochrane review of 18 studies found zinc lozenges (at least 75mg/day) administered within 24 hours of the onset of symptoms reduced the duration of cold symptoms in healthy people. Also, zinc was shown to inhibit the activity and replication of another coronavirus (SARS-CoV which caused an outbreak in 2002) in the laboratory.

Selenium is basically another trace element naturally present in the human body. Some studies have investigated its role in enhancing immune system function through various ways and results were very promising. Dietary selenium has been found to play a role in the immune treatment of viral and bacterial infections. Dietary selenium specifically can support the formation and multiply of T-lymphocytes and differentiation of T-helpers to fight of infection with minimal risk of attacking the body’s own cells.

Selenium can act as an antioxidant in the extracellular space, the cell cytosol, in association with cell membranes and specifically in the gastrointestinal tract, all with potential to influence immune processes. Selenium influences both the innate, “nonadaptive” and the acquired, “adaptive” immune systems. The innate immune system includes barriers to infection and nonspecific effector cells such as macrophages. Both the T and B lymphocytes form the major effector cells of the acquired system that mature with exposure to immune challenges. These processes can be improved by selenium supplementation. Foods high in selenium include nuts, tuna, oysters, beef, chicken, tofu, whole wheat pasta, shrimp, and mushrooms.

Scientists have found that people who are malnourished or follow poor diet habits depleted of essential nutrients, are more prone to develop infections/ diseases than those who don’t. So, following a healthy diet is very important as our immune system needs adequate nourishment and nutrients to fuel itself and fight off foreign intruders and disease.

Fahmida hashem; Sr. nutrition Consultant