Feeding the immune system: the role of micronutrients in restoring resistance to infections.

Abstract

The immune system protects the body against pathogens and cancer cells, thereby defending it against infections and diseases via three main components: epithelial barriers, immune cells and proteins including antibodies. Immune defences are constantly active and consist of a complex network of coordinated biological responses. Therefore, the immune system needs to be fed properly with energy sources and essential micronutrients serving as cofactors in the development, maintenance and expression of the immune response. The general nutritional status of an individual modulates immune functions, and immunocompetence is regarded as a measure of adequate nutrition. Low levels of vitamins, minerals and trace elements lead to suppressed immunity, predisposing individuals to infections, which in turn aggravate the nutritional status, leading to a vicious cycle. Supplying the deficient micronutrients with the diet or a dietary supplement can re-establish immune function. A sufficient and balanced diet should cover the overall micronutrient requirements. However, many population segments both in developing and industrialized countries do not get adequate amounts of essential micronutrients through the diet. Current environmental and geopolitical developments (i.e. global economic crisis, rice crisis and other food shortages, the increase in maize cultivation for ethanol production, etc.) are exacerbating problems of nutritional status in many parts of the world and represent a serious threat to nutritional health. This review focuses on nutritional aspects of the immune system and discusses the roles of vitamins A, D, E, C, B6, B12 and folate as well as of the trace elements selenium, zinc, iron and copper in supporting the body's natural defence system and restoring resistance to infections by enhancing the three levels of immunity: epithelial barriers, immune cells and antibody production.

Essential Role of Vitamin C and Zinc in Child Immunity and Health

“…Finally, both vitamin C and zinc provide complementary antioxidant protection to exogenously derived and endogenously generated ROS. 12,36,152,153 There is, therefore, a good scientific rationale that the combination of vitamin C and zinc support immune functions and reduce the risk of infections as described further in the following sections.…”

“…4,5 Extensive research strongly suggests that nutrition in early life has a major effect on long-term health and well-being. 6 Negative consequences of an inadequate diet with insufficient micronutrient density include impairment of physical growth, 7,8 mental development 8 -10 and immune function, 11,12 resulting in higher infection rates.…”

Vitamins C, D and Zinc: Synergistic Roles in Immune Function and Infections

“…Over millions of years the human immune system (i.e., our defense arsenal) has co-evolved to meet various attackers and now ranges from simple physical barriers (skin, mucosa) to sophisticated cells as well as biological, chemical and nuclear weapons (antibodies, cytokines and free radicals respectively). Despite this complexity, the immune system can be described for educational purposes as consisting of three main layers, i.e., epithelial barriers (e.g., skin, mucosa); cellular defenses and humoral responses such as antibody production [1][2][3].…”

“…Immune cells, like other cell types, need to be fed: they require adequate supply of energy, macronutrients and micronutrients serving as cofactors in the development, maintenance and expression of the immune response. The contribution of the diet to immune function has become widely appreciated and the influence of various dietary components on specific aspects of immune function has been extensively reviewed [2,6,7]. It is now generally recognized that the nutritional status of a person modulates his or her immunity and in fact, immunocompetence can be regarded as a measure of adequate nutrition.…”

“…Vitamin C is a cofactor for several enzymes involved in the biosynthesis of collagen, carnitine, and neurotransmitters; it's a water-soluble antioxidant and enhances gastrointestinal absorption of dietary non-heme iron. Marginal deficiency results in fatigue, lack of well-being, poor concentration whereas severe deficiency will cause weakening of collagenous structures, causing tooth loss, joint pains, bone and connective tissue disorders (e.g., impaired bone growth and disturbed ossification), poor wound healing and a compromised overall immunity [2,8]. Vitamin D (calciferol) is a fat-soluble vitamin.…”