In the new coronavirus (COVID-19), immunonutrition is attracting attention so much, as it takes time to confirm the safety and efficacy of vaccines, and also because there are still no effective therapeutic drugs for COVID-19. In particular, the importance and urgency of immunonutrition research is increasing due to the high rate of severity in older people aged 65 and over.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7211076/
The case fatality rate of COVID-19 increases with age. Reported rates are 0.2% for those aged 50-59, 0.4% for those aged 60-69, 1.3% for those aged 70-79, and 3.6% for those aged 80 and over.
Vitamin C, vitamin D, and zinc are the most important immunonutrition agents. The following is typical findings on each agent.
Role of vitamin C
Vitamin C has been confirmed to be effective in the treatment of pneumonia. Vitamin C is involved in maintaining and enhancing the activity of neutrophils, which are one of lymphocytes responsible for immune function, so it has the effect of enhancing immune function and resistance to viruses. In terms of potential mechanisms, it is well recognized that infectious diseases increase oxidative stress. Infections usually activate phagocytes that release active oxygen, which is an oxidising agent. Vitamin C becomes a well-known antioxidant that can cancel out these effects.
Role of vitamin D
Vitamin D receptors are expressed in many immune cells, and vitamin D is converted to 25 (OH) D3 in the liver and into an active form of 1,25 (OH) 2D3 in the function of immune cells. Vitamin D deficiency increases the risk of acute respiratory infections, and vitamin D metabolites are known to modulate the expression and secretion of inflammatory cytokines such as interferon IFN-γ, CXCL8, CXCL10 and chemokines, IL-6, and the tumor necrosis factor TNF-α.
The role of zinc
Zinc deficiency is known to cause impaired cellular immunity, including thymus atrophy with cd4+, CD8+ T-cell reduction, reduced peripheral blood lymphocyte count, reduced cytokine production from helper T-cells, reduced cytotoxic activity of NK cells, and inhibition of the formation of neutrophil extracellular traps (networks that bind to pathogens).