With the cold and flu season approaching, practitioners will start to see many children with upper respiratory tract infections (URTIs) coming through their doors. In fact, children can be expected to contract as many as five to 10 colds in the space of a year, as they have not yet developed immunity to the vast number of viruses that cause the ailment. Flavonoids such as quercetin and essential nutrients including vitamin A are often overlooked when supporting children’s immune health.
Quercetin, a potent flavonoid, has several actions that account for its beneficial effect on immune system health. As a mast cell and basophil stabiliser, quercetin inhibits histamine release providing an anti-allergic effect.
Additional anti-allergic effects are provided by the inhibition of inflammatory enzymes, prostaglandins and leukotrienes. Quercetin may also reduce the replication and infectivity of viruses including herpes simplex virus (HSV)-1, poliovirus type 1, parainfluenza virus type 3 (Pf-3) and respiratory syncytial virus (RSV), according to in vitro research.
A recent meta-analysis found that flavonoids, including quercetin, are important supplements to employ to decrease URTI incidence. Multiple randomised-controlled trials (RCTs) incorporated as a part of the meta-analysis also showed reduced sick days from work, and a positive effect on counts of natural killer (NK) cell, neutrophils, interleukin (IL)-6, IL-8, IL-10 and tumour necrosis factor (TNF)-alpha with the use of quercetin over a three to five week time period.
Vitamin A is also a particularly important nutrient for children, with a Cochrane review finding vitamin A supplementation effective in reducing all-cause mortality in children under five years by 24% compared to no treatment. Supplementation in children increases serum vitamin A levels and markers of immune function, including complement C3 and secretory immunoglobulin A (sIgA).
Vitamin A is required for innate immunity and the maintenance and regeneration of mucosal barriers that may be damaged in their role as the first line of defence in infection.
Vitamin A is also crucial for adaptive immunity and is involved in the development and activation of T-cells and B-cells.[7,8] A deficiency of vitamin A may impair the function of neutrophils, macrophages, T-cells, B-cells and NK cells.
Current evidence also shows that vitamin A helps to relieve clinical signs and symptoms of pneumonia in children, as well as shortening hospital stay, according to a 2018 meta-analysis of 15 RCTs and 3,021 children in total.
Incorporating quercetin and vitamin A as a part of a holistic and evidence-based treatment should be considered as a part of regimes for children who present with URTIs this coming cold and flu season.
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- Somerville VS, Braakhuis AJ, Hopkins WG. Effect of flavonoids on upper respiratory tract infections and immune function: a systematic review and meta-analysis. Adv Nutr 2016;7:488-497. [Full Text]
- Imdad A, Herzer K, Mayo-Wilson E, et al. Vitamin A supplementation for preventing morbidity and mortality in children from 6 months to 5 years of age. Cochrane Database Syst Rev 2010;(12):CD008524. [Abstract]
- Lin J, Song F, Yao P, et al. Effect of vitamin A supplementation on immune function of well-nourished children suffering from vitamin A deficiency in China. Eur J Clin Nutr 2008;62(12):1412-1418. [Abstract]
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- Higdon J. Vitamin A. Micronutrient information center, Linus Pauling Institute 2000 (reviewed 2015). [Source]
- Hu N, Li QB, Zou SY. Effect of vitamin A as an adjuvant therapy for pneumonia in children: a meta-analysis. Zhongguo Dang Dai Er Ke Za Zhi 2018;20(2):146-153. [Abstract]