Common cold is a general term used for mild upper respiratory illnesses consisting of a heterogeneous group of self-limited infection caused by several viruses. Common colds have a great economic burden on societies as it causes work absenteeism impairing the quality of life. Therefore, treatments that reduce the frequency of infection and lessen the severity of symptoms or shorten the duration of common colds are of high importance both for the individual and the society.

Several environmental factors, such as a stressful lifestyle can weaken the immune defense system, resulting in an increased risk of common cold. Natural killer cell (NK cell) activity and salivary immunoglobulin A (IgA) are very important in the prevention of common colds. The immune system is a complex network of specialized tissues, cells, organs and chemicals that protects the host from infectious agents and other harmful damages. These defense mechanisms are very complex and can be described in three main clusters: physical barriers, and innate and adaptive immunity.

The first barrier against “attackers” consists of physical barriers, mucus secretion and the acidity of the stomach. Innate immunity is the second barrier that includes immune system cells, such as NK cells, cytokines, macrophages and neutrophil granulocytes. Adaptive immunity is the third barrier to acquire infection and is attained later in life, such as after an immunization or fighting off an infection successfully. It holds a memory of all the attackers it has handled and this accelerates antibody production, which includes lymphocytes T and lymphocytes B.

Several alternative and nonpharmacological approaches for prevention and treatment of the common cold are proposed as intakes of some nutrients, i.e. zinc, iron, copper, selenium, b-carotene, vitamins A, D, C, and E, folic acid, and botanicalsas Echinacea. Vitamin C, vitamin D, and zinc have specific EFSA (European Food Safety Authority) scientific opinion on the normal function of the immune system. Also, vitamins C and D, zinc, and Echinacea have evidence-based efficacy on immune system barriers. The current review includes 82 eligible studies which considers the preventive role of these nutrients in immune clusters and in the common cold to offer guidance on dosage and assumption of these nutrients.

Adequate intake of zinc maintains the physical barriers and also the integrity of mucosal membrane Zinc supplementation improves immune functions, which includes delayed cutaneous hypersensitivity in children. It also improves delayed-type hypersensitivity in children supplemented with 10 mg/day. Supplementation of zinc improves natural killer cells activity and controls antibody-mediated humoral immune responses.

Few clinical trials have demonstrated that 400 IU/d vitamin D supplementation is required for the prevention of respiratory infections and reduction of the events related to respiratory tract infections.

Regular supplementation of vitamin C (1 to 2 g/day) has shown that vitamin C can reduce the duration and the severity of common cold in adults by almost 8% and in children by 14%. Also, the supplementation of zinc might shorten the duration of common colds by almost 33%. Common cold patients should be instructed to consume zinc within 24 hours of onset of symptoms. Vitamin D supplementation can protect against common cold overall, considering its baseline levels and age. Patients who are with vitamin D deficiency and do not receive bolus doses are the most benefited. Prophylactic treatment with Echinacea extract (2400 mg/day) for more than 4 months are beneficial for preventing and treating common cold.

Thus, the review concludes that the current evidence of effectiveness for vitamins C and D, zinc and Echinacea in common cold patients is encouraging and should try them for preventing or treating their common colds.

Source: Rondanelli M, Miccono A, Lamburghini S, et al. Self-Care for Common Colds: The Pivotal Role of Vitamin D, Vitamin C, Zinc, and Echinacea in Three Main Immune Interactive Clusters (Physical Barriers, Innate and Adaptive Immunity) Involved during an Episode of Common Colds-Practical Advice on Dosages and on the Time to Take These Nutrients/Botanicals in order to Prevent or Treat Common Colds. Evid Based Complement Alternat Med. 2018;2018:5813095. Published 2018 Apr 29. doi:10.1155/2018/5813095