A Review of Micronutrients and the Immune System–Working in Harmony to Reduce the Risk of Infection

Abstract

Immune support by micronutrients is historically based on vitamin C deficiency and supplementation in scurvy in early times. It has since been established that the complex, integrated immune system needs multiple specific micronutrients, including vitamins A, D, C, E, B6, and B12, folate, zinc, iron, copper, and selenium, which play vital, often synergistic roles at every stage of the immune response. Adequate amounts are essential to ensure the proper function of physical barriers and immune cells; however, daily micronutrient intakes necessary to support immune function may be higher than current recommended dietary allowances. Certain populations have inadequate dietary micronutrient intakes, and situations with increased requirements (e.g., infection, stress, and pollution) further decrease stores within the body. Several micronutrients may be deficient, and even marginal deficiency may impair immunity. Although contradictory data exist, available evidence indicates that supplementation with multiple micronutrients with immune-supporting roles may modulate immune function and reduce the risk of infection. Micronutrients with the strongest evidence for immune support are vitamins C and D and zinc. Better design of human clinical studies addressing dosage and combinations of micronutrients in different populations are required to substantiate the benefits of micronutrient supplementation against infection.

Evidence that Vitamin D Supplementation Could Reduce Risk of Influenza and COVID-19 Infections and Deaths

“…Several reviews consider the ways in which vitamin D reduces the risk of viral infections [9][10][11][12][13][14][15][16][17]. Vitamin D has many mechanisms by which it reduces the risk of microbial infection and death.…”

“…Vitamin D can reduce the production of pro-inflammatory Th1 cytokines, such as tumor necrosis factor α and interferon γ [31]. Administering vitamin D reduces the expression of pro-inflammatory cytokines and increases the expression of anti-inflammatory cytokines by macrophages ( [17] and references therein).…”

“…Better design of human clinical studies addressing dosage and combinations of micronutrients in different populations are required to substantiate the benefits of micronutrient supplementation against infection." [17].…”

COVID-19: is there a role for immunonutrition, particularly in the over 65s?

“…One recent review 25 identified that an array of micronutrients are required to meet the complex needs of the immune system, including vitamins A, D, C, E, B 6 , B 12 , folate, copper, iron, zinc and selenium, with many of these having potential synergistic relationships. Of the evidence, however, it was concluded that the largest body of evidence related to immune function existed for vitamin C, D and zinc.…”

“…Of the evidence, however, it was concluded that the largest body of evidence related to immune function existed for vitamin C, D and zinc. 25 Hereon we subsequently focus on these nutrients with specific reference to the evidence on respiratory health.…”