Respiratory viral infections in children with asthma: do they matter and can we prevent them?

Ahanchian, Hamid; Jones, Carmen M; Chen, Yueh-sheng; Sly, Peter D

Malnutrition is the most common cause of immune deficiency worldwide and a balanced diet is fundamental for a healthy immune system. Vitamin D deficiency has been associated with increased risk of infections, earlylife wheeze and reduced asthma control [69, 70] . Vitamin A derivatives are involved in the regulation of the immune system and tissue inflammation as well as prevention of respiratory infections [71] . Zinc, selenium and other trace elements are necessary for function of both innate and adaptive immune function. A high intake of fruit and vegetables ensures adequate consumption of nutrients and antioxidants and appears to be beneficial for asthma. Although recent reviews have shown that zinc [72] , garlic [73] , Echinacea purpurea [74] or Ginseng [75] supplementation for several months may reduce cold incidence, there is insufficient evidence to recommend any vitamin or mineral supplementation in the management of asthmatic children without nutrient deficiency [76, 77] . However, a large controlled trial showed Echinacea was ineffective in reducing infection rate or symptom severity of HRV infection in healthy young adult volunteers [78] . Vitamin C supplementation failed to reduce the incidence of colds in the general population except in those exposed to short periods of extreme physical stress [79] . Finally, it is worth remembering that infants who are not breastfed have significantly higher risk of respiratory, gastrointestinal, and other infections, as breast milk is a biologically active substance containing antimicrobial and immunomodulatory elements [80] [81] [82] .