Blackmores Institute

Selenium is an essential trace element for mammalian redox biology. Numerous epidemiological studies have shown that selenium deficiency is associated with an increased risk of developing several pathologies, including cancers, neurogenerative diseases, cardiovascular disorders and infectious diseases, with selenium supplementation able to reverse or reduce these risks reported in many human or animal models according to the review.“Selenium deficiency creates a weakening of defences against infectious diseases by reducing selenoprotein expression. During viral infections, there are many ways that the host metabolism could be affected, leading to a dysregulation of redox homeostasis,” the authors explained.“Viral pathogens induce oxidative stress via the increased generation of reactive oxygen species (ROS) and the alteration of cellular ROS scavenging systems. As part of antioxidant defence, selenoproteins, play an important role in controlling oxidative stress.”According to the authors, most of the beneficial effects of selenium are due to its incorporation in the form of selenocysteine into an essential group of proteins that are called selenoproteins. “Selenoproteins are present in many organelles or cellular compartments, with a specific tissue distribution and sensitivity to selenium level changes and are therefore important components of antioxidant defence systems maintaining redox homeostasis, which also include catalase, superoxide dismutase, glutathione, vitamin E, carotenoids, and ascorbic acid.”The review explains that ROS are produced during viral infections with both beneficial and deleterious consequences for the cell and while the mechanisms of ROS generation by the various viruses are diverse, it has been seen in several cases the host antioxidant defence enzymes, and especially members of the selenoproteome, are targeted. “Food is the primary source of selenium intake for mammals, but only five molecules (selenocysteine, selenomethionine, selenoneine, selenite, and selenate) constitute the bioavailable selenium in food intake. The recommended daily intake of selenium in adults is comprised between 50 and 70 μg per day,” the authors said.“Importantly, the concentration of selenium measured in the soil and water determines its levels in the living organisms and crops growing in these territories, and notably the components of the human food chain, including microorganisms, plants, cereals, vegetables, fruits, farm animals, etc.”Acknowledging that viral infections lead to diseases characterised by a broad spectrum of clinical symptoms, the review notes that oxidative stress appears to be key indicator of infection and ROS can enhance viral replication leading to an amplification loop.“Another important parameter for viral replication and pathogenicity is the nutritional status of the host. Viral infection simultaneously increases the demand for micronutrients and causes their loss, which leads to a deficiency that can be compensated by micronutrient supplementation,” the authors concluded.Source:
 Nutrients 2019. DOI: <a href="https://doi.org/10.3390/nu11092101">10.3390/nu11092101</a>

Being deficient in selenium could lower the body’s defences to viruses such as influenza according to a review published in the journal, Nutrients.

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