The immune systems of children undergo tremendous change and maturation in the first years of life and are extremely sensitive to both exogenous and endogenous signalling. During these developing years, children are particularly susceptible to infections. The most common conditions that affect the immune systems of children include viral infections such as the common cold and influenza, as well as bacterial infections such as ear and throat infections. Vitamin C and zinc have both been shown to support immune health in children and reduce the incidence of the common cold.[3-12]
Unlike most mammals, humans cannot synthesise vitamin C from glucose; this has been described as an inborn metabolic error and it makes vitamin C an essential nutrient. Also known as ascorbic acid, vitamin C is a powerful water-soluble antioxidant. High (millimolar) concentrations are maintained in cells and tissues with the highest concentrations found in leukocytes, eyes, the adrenal and pituitary glands and the brain. Research shows that vitamin C supports numerous aspects of both innate and acquired immunity including the production and function of leukocytes, while also enhancing cellular motility, chemotaxis, phagocytosis and delayed-type hypersensitivity.[4,5]
Optimal vitamin C intake may help to protect cells from free radical damage including cells involved in immunity such as neutrophils, and mononuclear phagocytes. Vitamin C regenerates other antioxidants including alpha-tocopherol, thus having an indirect positive effect on immunity. And, it scavenges free-radical oxygen and nitrogen species including superoxide, hydroxyl, peroxyl and nitroxide radicals, as well as non-radical reactive species including singlet oxygen, peroxynitrite and hypochlorite.
While the exact dosage and frequency of intake has not yet been established, research has shown that supplementation with vitamin C can reduce the severity and duration of the common cold. A Cochrane review found that regular vitamin C supplementation reduces the duration of common cold episodes in children. Infections and stress reduce vitamin C concentrations as measured in the level of leukocytes and plasma.
Concentrations of zinc in the body also decline rapidly during stress and infection. Zinc is vital for maintaining both innate and acquired immunity; even a small deficiency can impair numerous aspects of immune function and may lead to excessive inflammation.
Research with human cells and animal studies shows that the protein NF-kB attracts zinc into the immune cells that respond fastest to fight infection - which may be a clue as to why it is advised that zinc is taken early on at the first signs of symptoms. Once inside, zinc then slows the NF-kB pathway and the immune response, thus limiting inflammation in a feedback loop, preventing the process from becoming uncontrolled. While inflammation is vital to the immune function, if unchecked, it can cause damage to other cells. Incidentally, NF-kB is also involved in atherosclerosis, which has also been linked to zinc deficiency.
Zinc deficiency may impair the function of the epithelial barrier and reduce cell-mediated immune responses, T cells, macrophage function, natural killer cell activity and antibody-dependent cytotoxicity. Compared to adults, children have an increased requirement for zinc and are at an increased risk of zinc deficiency. In children, supplementation with zinc has shown to reduce the severity and duration of the common cold.
When used together in supplemental form, vitamin C and zinc have also seen positive results in the amelioration of symptoms of the common cold. Other research shows that vitamin C plus zinc significantly reduced rhinorrhoea over five days of treatment. Furthermore, relief of symptoms was faster than placebo and supplements were well tolerated.
Given the burden associated with the common cold and other bacterial infections in children, supplementation with vitamin C plus zinc may represent an efficacious measure, with a good safety profile, against these infectious viral and bacterial diseases.
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- Common childhood infections. American Academy of Paediatrics 2005. Viewed 21 Jan 2014, [Full Text]
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- Drake VJ, Angelo F, Gombart AF. Immunity in depth. Linus Pauling Institute. Oregon State University 2015. Viewed 21 Feb 2018, [Full Text]
- Wintergerst ES, Maggini S, Hornig DH. Immune-enhancing role of vitamin C and zinc and effect on clinical conditions. Ann Nutr Metab 2006;50(2):85-94. [Abstract]
- Braun L, Cohen M. Herbs and natural supplements: an evidence-based guide, 4th ed. Sydney: Churchill Livingstone Elsevier, 2014. [Abstract]
- Hemila H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev 2013;(1):CD000980. [Abstract]
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- Larson CP, Roy SK, Khan AI, et al. Zinc treatment to under-five children: applications to improve child survival and reduce burden of disease. J Health Popul Nutr 2008;26(3):359-365. [Abstract]
- Kurugöl Z, Akilli M, Bayram N, et al. The prophylactic and therapeutic effectiveness of zinc sulphate on common cold in children. Acta Paediatr 2006;95(10):1175-1181. [Abstract]
- Maggini S, Beveridge S, Suter M. A combination of high-dose vitamin C plus zinc for the common cold. J Int Med Res 2012;40(1):28-42. [Abstract]