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Back-to-School – Boost Immunity for the Cold & Flu Season

Back-to-School – Boost Immunity for the Cold & Flu Season
Back-to-School - Boost Immune System Health for the Cold & Flu Season - Best Laboratory Test Panel
By Med Support News August 3, 2025

Back-to-School - Boost Immune System Health for the Cold & Flu Season - Best Laboratory Test PanelBack-to-School – Boost Immunity for the Cold & Flu Season

Going back to school coincides with the start of the cold and flu season, so consider recommending extra immune support for your patients soon!

The common cold is the most frequent illness. Adults typically experience 1–3 colds per year, whereas children have an average of five but could have up to eleven colds annually.1,2 More than 200 viruses, including the influenza viruses, are known to cause symptoms of the common cold. Therefore, supporting the optimal health and function of the immune system could be an excellent strategy to reduce the severity, duration, and possibly the number of colds this year since it is impossible to avoid exposure to all viruses.

This article explores the latest research on natural options that could benefit optimal immune function in your pediatric and young adult patients during the cold and flu season.

Back-to-School - Boost Immune System Health for the Cold & Flu Season - Best Test Panel

Back-to-School Nutrition and the Common Cold

Symptoms of the common cold include nasal congestion, sneezing, facial pressure, loss of taste, loss of smell, runny nose, sore throat, cough, headache, muscle aches, pain, discomfort, and fever. The common cold usually lasts less than ten days but can significantly disrupt life for your patients and their parents.3

Micronutrients, including iron, zinc, selenium, copper, chromium, and vitamins A, C, D, & E, are essential for the optimal function of the immune system. No single food contains all the nutrients required for immune function; therefore, recommending a balanced, whole-food diet daily while fostering a healthy appetite and optimal digestion can provide the necessary components involved in the immune response.4

To date, clinical trials studying the effects of nutrients on immune function and specific illnesses mostly include adults. Some clinical trials have included children, and the available evidence is reviewed below.

Back-to-School - Boost Immune System Health for the Cold & Flu Season - Best Laboratory Test PanelDoes Supplemental Vitamin C Boost Pediatric Immunity?

Research indicates that vitamin C is a highly efficient and water‐soluble antioxidant that protects against the systemic oxidative stress produced during an infection. Furthermore, evidence shows that vitamin C deficiency significantly impairs immune function.5,6

Dozens of studies note that vitamin C naturally and beneficially impacts the ability of white blood cells to respond to an infection, boosts antibody production, affects the replication of viruses, and supports the production of interferon, all of which could reduce the burden of a viral infection. White blood cells also have a specialized transport system that regenerates vitamin C, enhancing the antioxidant benefits.5,6

Overall, clinical research suggests vitamin C supplementation could be more beneficial for children at this time of year than for adults. A Cochrane review confirms that regular vitamin C supplementation significantly reduces the duration and severity of the common cold in children.5

The data demonstrate that supplementation with 200 mg of vitamin C daily minimizes the duration and severity of upper respiratory tract infections, including the common cold, by 14-18% in children. Divided doses of 1 to 2 grams of vitamin C per day in children shortened the duration of a cold by 18%. Some studies suggest that regular vitamin C supplementation in appropriate doses could reduce the duration of colds by up to 21% in children.5

While vitamin C reduces the duration and severity of upper respiratory tract infections, the research does not yet suggest that vitamin C can reduce the number of colds experienced by children each year.5

Back-to-School - Boost Immune System Health for the Cold & Flu Season - Best Laboratory Test PanelProbiotics Plus Vitamin C for Optimal Immune System Health When Going Back-to-School

Two placebo-controlled therapeutic trials assessing the efficacy of probiotics plus 50 mg of vitamin C in children were published in 2015 and 2021 and known as the PROCHILD and PROCHILD-2 studies. The results of the two clinical studies suggest that a therapeutic combination of probiotics and vitamin C reduces both the incidence and duration of upper respiratory tract infections in children.7-9

Furthermore, the significant reduction in the incidence and duration of symptoms in preschool children receiving the therapeutic probiotic and vitamin C combination was associated with fewer doctor visits and a 47% reduction in antibiotic prescriptions.9

More research is needed, but, in age-appropriate and regular doses, combining vitamin C and probiotics appears to be a well-tolerated preventive option to support a reduction in the incidence, severity, and duration of pediatric upper respiratory infections, including the common cold.5,7-9

Back-to-School - Boost Immune System Health for the Cold & Flu Season - Best Laboratory Test PanelBack-to-School – The Best Natural Probiotics for Pediatric Immunity

As noted in the section above, data from the PROCHILD and PROCHILD-2 studies show that combining probiotics with vitamin C significantly reduces the severity, duration, and incidence of respiratory infections, including the common cold.9

Research also suggests that infants and children with a respiratory tract infection who supplement with probiotics alone decrease their risk of being prescribed antibiotics by 41-42% compared to placebo.9,10 Reducing the number of antibiotics taken during childhood could significantly reduce the risk of side effects and long-term damage to the gut microbiome.11

The specific strains of probiotics used in the PROCHILD and PROCHILD-2 studies include Lactobacillus acidophilus CUL21, Lactobacillus acidophilus CUL60, Bifidobacterium bifidum CUL20, and Bifidobacterium animalis subsp. lactis CUL34.9

Other probiotic strains administered to children in clinical trials showing immune benefits include:

  • Lacticaseibacillus rhamnosus GG (LGG)
  • Lacticaseibacillus paracasei subsp. paracasei DN-114 001/CNCM I-1518
  • Bifidobacterium longum BB536
  • Lactobacillus plantarum HEAL9
  • Lactobacillus paracasei (8700:2 or N1115)9,10

Most beneficial studies administered 109 or 1011 total colony‐forming units (CFU) of one or two probiotic strains each day for more than three months.10

Back-to-School - Boost Immune System Health for the Cold & Flu Season - Best Laboratory Test PanelDietary Vitamin A Gets an A+ for Immune Support When Going Back-to-School!

Vitamin A is a fat-soluble vitamin required for optimal growth & development, cellular communication, immune function, and skin health.12,13 Vitamin A is also crucial for vision since it is a component of the protein that responds to light entering the eye.12

Vitamin A is available via the diet and supplements as preformed vitamin A and provitamin A carotenoids. Good sources of preformed vitamin A include dairy products, eggs, fish, and organ meats (liver). Good sources of provitamin A carotenoids include colorful plant foods, such as sweet potatoes, pumpkin, spinach, and carrots.12

Regarding immune function, vitamin A offers antioxidant benefits, immunomodulating effects, antiviral activity, enhanced natural barriers (healthy skin), and improved cell signaling.3 Vitamin A also beneficially affects natural killer (NK), T-reg, and T-helper cell activity; the differentiation of immune cells, antibody production, and the phagocytosis of macrophages.14

Recent surveys of children in China suggest low blood levels of vitamin A are associated with a high incidence of recurrent respiratory tract infections (RRTIs). Specifically, the data shows that children with a low blood vitamin A concentration during an active respiratory tract infection are more likely to develop recurrent infections. Furthermore, a low intake of foods rich in vitamin A also correlates with the number of RRTIs in children.15,16

Despite the known effects of vitamin A on immune function and the association between suboptimal vitamin A status and respiratory infections, clinical studies assessing the beneficial effects of vitamin A supplementation on colds and the flu have had mixed results. Some studies show no benefit, while others suggest that vitamin A supplementation for immune support is protective.17,18 A study by Zhang et al. suggests that excessive vitamin A supplementation may increase the risk of respiratory infections.19

The amount of vitamin A consumed daily by the study participants could contribute to the incongruent results of the studies to date. Thus, it is likely best to ensure pediatric patients are getting the Recommended Daily Allowance (RDA) for vitamin A from their diet and consider supplementation to prevent deficiency or insufficiency only when needed.17

Back-to-School - Boost Immune System Health for the Cold & Flu Season - Best Laboratory Test PanelBack-to-School – Optimal Vitamin A Intake for Immune System Support

The RDA for vitamin A varies based on age. The RDA for 4 – 8-year-old children is 400 mcg RAE (retinol activity equivalents). The RDA for 9 – 13-year-old children is 600 mcg RAE. The RDA for 14 – 18-year-old males is 900 mcg RAE. The RDA for 14 – 18-year-old females who are neither pregnant nor breastfeeding is 700 mcg RAE.12

High doses of preformed vitamin A can cause birth defects, so it should never be consumed in large quantities by cycling females or during or just before pregnancy. In adults and college-age students, the RDA for males is 900 mcg RAE, and 700 mcg RAE for females who are neither pregnant nor breastfeeding.12

Please note that children and adults can consume too much Vitamin A. High doses of preformed vitamin A cause vitamin A toxicity. Therefore, always ensure dietary intake and supplemental doses of vitamin A are appropriate for the age and health status of every patient.12,20

Back-to-School - Boost Immune System Health for the Cold & Flu Season - Best Laboratory Test PanelVitamin D for Back-to-School Immunity During the Cold & Flu Season

One of the most important benefits of adequate vitamin D is the optimal regulation of the immune system. Vitamin D deficiency is associated with increased susceptibility to infections and an impaired immune response.3,19 Research also shows vitamin D deficiency is a risk factor for recurrent respiratory tract infections (RRTIs) in children.16,20,21

Among its many actions in the body, vitamin D enhances the immune response by promoting the synthesis of peptides with powerful antimicrobial activity, including cathelicidin and LL37 protein. Vitamin D also directly impacts the:

  • Signaling mechanisms downstream of the T-cell-receptor (TCR) of T-cells
  • Promotion of Treg responses
  • Maturation of dendritic cells
  • Expression of Nrf2
  • Enhancement of epithelial barrier function in both the skin and the lungs
  • Maturation of type II pneumocytes in the lungs
  • Promotion of surfactant production in the lungs
  • Control of calcium-mediated and redox signaling
  • Modulation of cytokine secretion
  • Recruitment of eosinophils in the airways20,22

Moreover, research shows children with recurrent diseases of the airways often have sub-optimal levels of both vitamin D and vitamin A, and nutrient replenishment results in decreased numbers of infections and an overall improvement of health. Vitamin D supplementation during a respiratory infection can significantly reduce the duration and severity of the infection while improving the quality of life in those with low levels.3,20

Several studies demonstrate that vitamin D supplementation improves lung function in children with bronchiolitis and reduces the likelihood of developing respiratory infections in general. Bronchiolitis can be caused by the same viruses that cause colds, including RSV, rhinovirus, and coronavirus.20,23

Please note that patients can take too much vitamin D, so be mindful of the Adequate Intake (AI) and Recommended Daily Allowance (RDA) for each age group. The current AI for ages 0-12 months is 10 mcg (400 IU) per day, and the RDA for ages 1 – 70 years is 15 mcg (600 IU) daily. Vitamin D is also naturally produced with sun exposure.24

Back-to-School - Boost Immune System Health for the Cold & Flu Season - Best Laboratory Test PanelImmune Support Protocols for the Back-to-School and Cold & Flu Seasons

Micronutrients are essential for the proper function of the immune system. Overall, micronutrients regulate innate and adaptive immunity, which include antibody production, cytokine activity, and the immune response of immune cells, including Th1 and Th2 lymphocytes.4 

Optimal dietary intake of or supplementation with the vitamins mentioned above, plus probiotics, could be a safe option to support the healthy function of the immune system in pediatric patients. Supplementation should only be considered in addition to a healthy diet, and dosages must be within the recommended upper safety limits set by the experts.21

Children and young adults also need to get adequate sleep, manage stress, stay physically active, and take precautions, such as washing their hands, to remain as healthy as possible when going back to school during the cold and flu season.25 Acute botanical remedies, including elderberry, could also be considered as part of a comprehensive immune support protocol.26,27

Back-to-School - Boost Immune System Health for the Cold & Flu Season - Best Laboratory Test PanelThe Best Test for Immune Resilience During the Cold & Flu Season – Salivary Secretory IgA (sIgA)

Secretory IgA (sIgA) is a biomarker that reflects the resilience of the mucosal immune response. It is synthesized by activated B cells along mucosal membranes in the oral cavity, nasal passages, gastrointestinal tract, respiratory tract, and the genitourinary tract. Since mucosal surfaces are exposed to the outside world, sIgA is an important part of the first line of immune defense against pathogens that cause infections, including viruses.28

When present in mucosal secretions, sIgA binds to infectious pathogens, thus preventing their adhesion and entrance into the body. The binding of sIgA to these pathogens then facilitates their elimination. Preventing the adhesion and adsorption of pathogenic organisms, while also facilitating their removal, is a phenomenon known as “immune exclusion.” Two additional methods by which sIgA reduces the likelihood of infection include direct interference with surface receptor binding and a reduction in the activation of pathogenic virulence factors.28

Secretory IgA production can be suppressed by stress and elevated cortisol levels.28 Keep your patients healthy year-round by testing for and optimizing the production of sIgA at least twice annually.

Back-to-School - Boost Immune System Health for the Cold & Flu Season - Best Laboratory Test PanelDiagnosTechs Test Panels That Assess Secretory IgA (sIgA) Levels

Total Salivary Secretory IgA (sIgA) is included with the:

Total Intestinal Secretory IgA (sIgA) is included with the:

Total Intestinal sIgA and Total Salivary sIgA can also be ordered as single tests.

Back-to-School - Boost Immune System Health for the Cold & Flu Season - Best Laboratory Test PanelTo place a test order, click here. As a reminder, DiagnosTechs will drop ship test kits directly to your patients. Select this option at the top of the order form.

Please visit our Provider Tools page for more information about choosing the right test and mucosal immunity.

Back-to-School - Boost Immune System Health for the Cold & Flu Season - Best Test PanelReferences:

  1. Passioti M, Maggina P, Megremis S, et al. The common cold: potential for future prevention or cure. Curr Allergy Asthma Rep. 2014;14(2):413. doi:10.1007/s11882-013-0413-5
  2. 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(3):488-497. doi:10.3945/an.115.010538
  3. Ciprandi G, Tosca MA. Non-pharmacological remedies for the common cold. Minerva Pediatr (Torino). 2023;75(1):75-86. doi:10.23736/S2724-5276.21.06312-6
  4. D’Auria E, Calcaterra V, Verduci E, et al. Immunonutrition and SARS-CoV-2 Infection in Children with Obesity. Nutrients. 2022;14(9):1701. doi:10.3390/nu14091701
  5. Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2013;2013(1):CD000980. doi:10.1002/14651858.CD000980.pub4
  6. Berger MM, Herter-Aeberli I, Zimmermann MB, et al. Strengthening the immunity of the Swiss population with micronutrients: A narrative review and call for action. Clin Nutr ESPEN. 2021;43:39-48. doi:10.1016/j.clnesp.2021.03.012
  7. Garaiova I, Muchová J, Nagyová Z, et al. Probiotics and vitamin C for the prevention of respiratory tract infections in children attending preschool: a randomised controlled pilot study. Eur J Clin Nutr. 2015;69(3):373-379. doi:10.1038/ejcn.2014.174
  8. Garaiova I, Paduchová Z, Nagyová Z, et al. Probiotics with vitamin C for the prevention of upper respiratory tract symptoms in children aged 3-10 years: randomised controlled trial. Benef Microbes. 2021;12(5):431-440. doi:10.3920/BM2020.0185
  9. Paduchová Z, Nagyová Z, Wang D, Muchová J. The impact of probiotics and vitamin C on the prevention of upper respiratory tract symptoms in two preschool children cohorts. Nutr Res Pract. 2024;18(1):98-109. doi:10.4162/nrp.2024.18.1.98
  10. Zhao Y, Dong BR, Hao Q. Probiotics for preventing acute upper respiratory tract infections. Cochrane Database Syst Rev. 2022;8(8):CD006895. doi:10.1002/14651858.CD006895.pub4
  11. McDonnell L, Gilkes A, Ashworth M, et al. Association between antibiotics and gut microbiome dysbiosis in children: systematic review and meta-analysis. Gut Microbes. 2021;13(1):1-18. doi:10.1080/19490976.2020.1870402
  12. Office of dietary supplements – vitamin A and carotenoids. NIH Office of Dietary Supplements. December 15, 2023. Accessed July 5, 2024. https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/
  13. Chen G, Weiskirchen S, Weiskirchen R. Vitamin A: too good to be bad?. Front Pharmacol. 2023;14:1186336. doi:10.3389/fphar.2023.1186336
  14. Spinas E, Saggini A, Kritas SK, et al. Can vitamin a mediate immunity and inflammation?. J Biol Regul Homeost Agents. 2015;29(1):1-6.
  15. Zhang X, Dai X, Li X, et al. Recurrent respiratory tract infections in children might be associated with vitamin A status: a case-control study. Front Pediatr. 2024;11:1165037. doi:10.3389/fped.2023.1165037
  16. Sun M, Yan Z, Sun R, et al. Dynamic monitoring and a clinical correlation analysis of the serum vitamin A, D, and E levels in children with recurrent respiratory tract infections. Am J Transl Res. 2022;14(5):3533-3538.
  17. Timoneda J, Rodríguez-Fernández L, Zaragozá R, et al. Vitamin A Deficiency and the Lung. Nutrients. 2018;10(9):1132. doi:10.3390/nu10091132
  18. Abdelkader A, Wahba AA, El-Tonsy M, et al. Recurrent respiratory infections and vitamin A levels: a link? It is cross-sectional. Medicine (Baltimore). 2022;101(33):e30108. doi:10.1097/MD.0000000000030108
  19. Zhang Y, Lu Y, Wang S, et al. Excessive Vitamin A Supplementation Increased the Incidence of Acute Respiratory Tract Infections: A Systematic Review and Meta-Analysis. Nutrients. 2021;13(12):4251. doi:10.3390/nu13124251
  20. Parisi GF, Carota G, Castruccio Castracani C, et al. Nutraceuticals in the Prevention of Viral Infections, including COVID-19, among the Pediatric Population: A Review of the Literature. Int J Mol Sci. 2021;22(5):2465. doi:10.3390/ijms22052465
  21. Pecora F, Persico F, Argentiero A, et al. The Role of Micronutrients in Support of the Immune Response against Viral Infections. Nutrients. 2020;12(10):3198. doi:10.3390/nu12103198
  22. Costagliola G, Nuzzi G, Spada E, et al. Nutraceuticals in Viral Infections: An Overview of the Immunomodulating Properties. Nutrients. 2021;13(7):2410. doi:10.3390/nu13072410
  23. Justice NA, Le JK. Bronchiolitis. In: StatPearls. Treasure Island (FL): StatPearls Publishing; June 26, 2023.
  24. Office of dietary supplements – vitamin D. NIH Office of Dietary Supplements. July 26, 2024. Accessed July 29, 2024. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/.
  25. McCarthy C. Boosting your child’s immune system. Harvard Health. July 17, 2023. Accessed July 30, 2024. https://www.health.harvard.edu/blog/boosting-your-childs-immune-system-202110122614.
  26. Solomonian L, Blesoff J, Garofalo L, et al. Naturopathic Management of Acute Pediatric Respiratory Infections: A Modified Delphi Study. J Integr Complement Med. 2023;29(3):181-195. doi:10.1089/jicm.2022.0669
  27. Hawkins J, Baker C, Cherry L, Dunne E. Black elderberry (Sambucus nigra) supplementation effectively treats upper respiratory symptoms: A meta-analysis of randomized, controlled clinical trials. Complement Ther Med. 2019;42:361-365. doi:10.1016/j.ctim.2018.12.004
  28. Assessing the impact of stress on the immune system. DiagnosTechs, Inc. May 9, 2020. Accessed March 26, 2025. https://www.diagnostechs.com/2020/03/30/30570/.