A 2017 review stated that vitamin C, vitamin D and the mineral zinc play a major role in the maintenance of an optimal immune system. These essential nutrients, through their complementary and synergistic effects, support components of both innate and adaptive immunity. Furthermore, zinc is actively used by cells of the immune system engaged in fighting infections, for instance, upper respiratory tract infections.

Researchers have also stated that ensuring adequate levels of micronutrients such as vitamin C, D and zinc may be particularly important in situations, such as when exposed to sudden temperature changes or when spending time in confined spaces, where the risk of spreading infectious diseases is high.

A 2010 article reported that deficiencies of micronutrients are emerging as the limiting factor in ensuring childrens optimal health. It was stated that a deficiency of zinc adversely affects the physical and mental growth of children and can impair their immune defenses. Nutrition should be the main vehicle for providing these essential nutrients; however, supplementation can represent a valid support method, especially in developing regions.

Source: 1.  Maggini S, Maldonado P, Cardim P, Fernandez Newball C, Sota Latino ER. Vitamins C, D and zinc: synergistic roles in immune function and infections. Vitam Miner. 2017;6:167.

2. Maggini S, Wenzlaff S, Hornig D. Essential role of vitamin C and zinc in child immunity and health. J Int Med Res. 2010;38(2):386-414.