Selenium’s protective role in infections and trauma

During infections and trauma, the body triggers a series of inflammatory processes, which are also associated with cascades of free radicals and the risk of oxidative stress. In such cases, the trace element selenium plays a crucial role: partly as a component of the immune system and in regulating inflammatory processes, and partly as a powerful antioxidant that counteracts damage to cells and tissues caused by free radicals. Evidence also suggests that selenium deficiency increases the risk of complications or severe outcomes from influenza, COVID-19, and other infections. The same applies to blood clots and physical trauma. Conversely, early selenium supplementation can reduce complications, shorten hospital stays, and lower overall mortality, as highlighted in a recent review article published in Antioxidants.

The immune system’s task is to combat infections and repair cellular damage quickly and efficiently. Infections can be caused by bacteria, influenza virus, or COVID-19. Physical trauma may occur as a result of complicated infections, or it may follow injuries, blood clots, strokes, and severe burns.
When the body is exposed to infections or trauma, the immune system initiates local inflammatory processes, and white blood cells release various cytokines that should ideally regulate these processes carefully. Many free radicals are also produced, and they attack pathogens like missiles. However, if the inflammatory response spirals out of control with cytokine storms and hyperinflammation, there is a risk of oxidative stress, where free radicals start attacking healthy cells and tissues as well.
Severe infections like sepsis, influenza, and COVID-19 can, for example, cause acute respiratory distress syndrome (ARDS) and failure in other organs. Overall, trauma is believed to be the tenth most common cause of death.

Critically ill patients often lack selenium

It is well known that vitamins and minerals play indispensable roles as cofactors and antioxidants that neutralize free radicals to maintain the right balance and prevent oxidative stress.
Selenium is part of various selenoproteins that are crucial for the immune system’s capacity and communication during inflammatory processes. Additionally, selenium is incorporated into unique antioxidants called GPXs, which neutralize free radicals.
Critically ill patients, however, often have low selenium levels for several reasons. First, the diet is frequently low in selenium. Second, the need for selenium increases significantly during inflammatory processes and for cellular protection against oxidative stress. Studies have shown that selenium levels in the blood can drop by 40-60% within 24 hours in patients admitted to intensive care units. Observational studies from ICUs have demonstrated that low blood selenium levels are associated with higher risks of complications, longer hospital stays, and increased mortality.

Selenium supplementation protects against complications and oxidative stress

Because selenium deficiency is so common, researchers have administered selenium supplements to critically ill patients in several studies. This especially boosts GPX antioxidant capacity, thereby reducing a range of cell and tissue damage caused by free radicals and oxidative stress.
Although studies have shown mixed results regarding the effect of selenium supplementation on overall survival in hospitalized trauma patients, early treatment with selenium appears to be beneficial, particularly for patients who are already deficient.
The effect can be further enhanced when selenium supplementation is combined with other antioxidants such as vitamin C, vitamin E, and zinc, which also support overall immune function. Together, selenium, vitamins C and E, and zinc reduce oxidative stress through multiple pathways and synergistic effects.
The new review article refers to several studies emphasizing the importance of preventing and monitoring selenium deficiency. Selenium supplementation can be a therapeutic strategy for critically ill patients, reducing both hospital stay and mortality. Several studies suggest that higher selenium doses (300-800 micrograms/day) for trauma patients yield the best results. It is also essential that selenium supplementation properly saturates selenoprotein P, a marker of blood selenium status, as well as GPX, which circulates in the blood. These biomarkers can be used to detect deficiency and monitor the effect of supplementation.

Widespread selenium deficiency and actual daily needs

Researchers focus on selenium because deficiencies are widespread in many parts of the world, due to selenium-poor soils, intensive farming methods, and dietary changes with less fish and offal. In Denmark, the official daily recommendation is 75-90 micrograms, but several studies suggest that around 100-150 micrograms per day are needed to saturate selenoprotein P, GPX, and other selenoproteins.
As mentioned, the requirement also increases during acute infections and trauma. The upper daily limit for selenium intake, according to the European Food Safety Authority (EFSA), is 300 micrograms.

References:

Jae-Gil Lee et al. Selenium as an Antioxidant: Roles and Clinical Applications in Critically Ill and Trauma Patients. A Narrative Review. Antioxidants 2025

Yu-Cheng Chiu et al. The influence of early selenium supplementation on trauma patients: A propensity-matched analysis. Frontiers. 2022

Simone Passarelli et al. Global estimation of dietary micronutrient inadequacies: a modeling analysis. The Lancet Global Health 2024