Can supplements enhance the immune system in the context of COVID-19? Original paper

Proper nutrition is essential to prevent and fight off viral infections. What supplements does the current body of evidence deem beneficial in supporting the immune system in the context of the COVID-19 pandemic?

This narrative review provided an overview of the current evidence for the use of nutraceuticals, probiotics, vitamins, and trace elements to support the immune system during the COVID-19 pandemic.

This review evaluated the following supplements that may warrant a closer look for management and prevention of COVID-19 infection:

• Vitamin D deficiency or insufficiency is associated with worse COVID-19 infection outcomes. Vitamin D was found to enhance the immune response to COVID infection when combined with high-dose vitamin C.
• Vitamin E had inconclusive evidence for use with COVID-19 infection, but it has been shown to protect against oxidative stress and enhance both adaptive and innate immunity.
• Vitamin and mineral deficiencies were associated with worse COVID-19 outcomes, and therefore, this review suggests multivitamin/multimineral supplementation in people with restricted or limited diets.
• Zinc deficiency impedes the immune response, and supplementation may improve symptom severity.
• Iron deficiency can increase the risk of respiratory infections, but iron overload can increase oxidative stress.
• Selenium inhibits nuclear factor kappaB (a regulator of innate immunity), which plays a role in the progression of COVID-19 infection.
• Calcium phosphate has been used to enhance the immune response to various vaccines, and in mice, it has been shown to activate innate and adaptive immunity.
• Probiotics have been reported to improve immunity, but little evidence currently exists on their usefulness for COVID-19 infection.
• Protein-rich foods and certain amino acids (arginine, glutamine, and nucleotides) are important not only for bodily health but also for a robust immune system.
• Polyphenols like curcumin and resveratrol have been shown to play a role in inhibiting inflammatory cytokines and may improve the innate immune response.
• Flavonoids such as naringin and naringenin may be effective in removing free radicals and the injuries caused by them.