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

Abstract

The immune system is a complex and sophisticated network of specialized tissues, organs, cells, proteins, and chemicals which has evolved in order to protect the host from a range of dangerous agents such as bacteria, virus, fungi, and parasites. There is a close relationship between nutritional status and immune function. Hence, immunocompetence can be regarded as a measure of adequate nutrition. Inter-individual variations in many immune functions exist within the normal healthy population and are due to age, genetics, gender, ethnic background, socioeconomic situation, diet, stress, habitual levels of exercise, alcohol consumption, smoking habits, etc. In addition, seasonal and temperature changes as well as being in crowded spaces (e.g., while commuting in public means of transportation, or working in open space offices) pose an additional burden on the immune system. Here we review the literature on the immune supportive properties of vitamins C, D and zinc and the impact of their supplementation in reducing the incidence or ameliorating symptoms of upper respiratory tract infections, which are among the most common infections in humans. Finally, we discuss their relevance in situations known to challenge the immune system such as exposure to temperature changes, to pollutants, or being in crowded spaces which serve as mixers where pathogens can stay suspended and transfer from host to host thereby increasing the risk of spreading infectious diseases because of close contact and long exposure.

Immune Function and Micronutrient Requirements Change over the Life Course

“…Age-related changes are compounded by certain lifestyle factors (e.g., diet, environmental factors, and oxidative stress) specific to each life stage that can influence and modify, in some cases suppressing, immune function. Accordingly, the risk and severity of infections such as the common cold and influenza (the most common illnesses in humans [ 3 ]), pneumonia and diarrheal infections also vary over a lifetime.…”

“…Optimal immune function is dependent on a healthy immune system. In turn, adequate nutrition is crucial to ensure a good supply of the energy sources, macronutrients and micronutrients required for the development, maintenance and expression of the immune response [ 3 ]. Micronutrients have vital roles throughout the immune system that are independent of life stage ( Table 1 ), and it has been determined that those most needed to sustain immunocompetence include vitamins A, C, D, E, B2, B6 and B12, folic acid, beta carotene, iron, selenium, and zinc [ 4 ].…”

The Role of Micronutrients in Support of the Immune Response against Viral Infections

“…It is today acknowledged that an adequate nutritional status is crucial for the development, maintenance, and expression of the immune response [ 5 , 6 ]. Micronutrients (i.e., vitamins and nutritionally essential minerals) influence and support every stage of the immune response.…”

Nutraceutical potentials of synergic foods: a systematic review

“…Vitamins C and D and zinc Improves immune functions and prevents infections [49] 8 Vitamin A and vitamin E Enhances vitamin A intestinal absorption, increased antioxidant capabilities, protect against some forms of cancer, and support a healthier gut [50,51] 9…”