The immune system requires essential nutrients to function efficiently. Inadequate intake and status of vitamins and trace elements may lead to suppressed immunity, which predisposes to infections and aggravates undernutrition. Available data indicate a role for vitamins A, B6, B12, C, D and E and folate and for the trace elements Se, Zn, Cu and Fe in the immune response. Evidence has accumulated that in human subjects these nutrients selectively influence the immune response, induce dysregulation of a coordinated host response to infections in the case of deficiency and oversupply, and that deficiency may impact on the virulence of otherwise harmless pathogens. Thus, micronutrients are required at appropriate intakes for the immune system to function optimally and contribute to the body's natural defences on three levels by supporting the physical barriers (skin and mucosa), cellular and humoral immunity. Vitamins A, C and E and the trace element Zn assist in enhancing the skin barrier function. The vitamins A, B6, B12, C, D and E and folic acid and the trace elements Fe, Zn, Cu and Se work in synergy to support the protective activities of immune cells. Finally, all these micronutrients, except vitamin C and Fe, are essential for antibody production.
The table summarises the most important roles of selected vitamins and trace elements in immune function(Reference Wintergerst, Maggini and Hornig1–Reference Maggini, Wintergerst, Beveridge and Hornig3).
Insufficient intake of micronutrients occurs in individuals with eating disorders, in smokers (both active and passive), in individuals with chronic alcohol abuse, in patients with certain diseases, during pregnancy and lactation, and in the elderly. With aging a variety of changes are observed in the immune system, which translate to less-effective innate and adaptive immune responses and increase susceptibility to infections. Overall, inadequate intake and status of vitamins A, B6, B12, C, D and E and folate and of the trace elements Se, Zn, Cu and Fe may lead to suppressed immunity, which predisposes to infections and aggravates malnutrition. Thus, supplementation with a combination of these selected micronutrients can support the body's natural defence system by enhancing all three levels of immunity: epithelial barriers; cellular immunity; antibody production.
