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Frequently Asked Questions about Allergies
Which supplements can help against colds and the flu?
Vitamin C, vitamin D, zinc, and other supplements may provide an edge against colds and the flu, but they should only serve to complement your main defensive arsenal: good hygiene, proper hydration, healthy diet, restful sleep, stress control, and exercise.
Human Effect Matrix
The Human Effect Matrix looks at human studies (it excludes animal and in vitro studies) to tell you what supplements affect allergies
|Grade||Level of Evidence [show legend]|
|Robust research conducted with repeated double-blind clinical trials|
|Multiple studies where at least two are double-blind and placebo controlled|
|Single double-blind study or multiple cohort studies|
|Uncontrolled or observational studies only|
Level of Evidence
? The amount of high quality evidence. The more evidence, the more we can trust the results.
Magnitude of effect
? The direction and size of the supplement's impact on each outcome. Some supplements can have an increasing effect, others have a decreasing effect, and others have no effect.
Consistency of research results
? Scientific research does not always agree. HIGH or VERY HIGH means that most of the scientific research agrees.
|Strong||- See study|
|Strong||- See study|
|Notable||Very High See all 4 studies|
- Mourtzoukou EG, Falagas ME. Exposure to cold and respiratory tract infections. Int J Tuberc Lung Dis. (2007)
- Foxman EF, et al. Temperature-dependent innate defense against the common cold virus limits viral replication at warm temperature in mouse airway cells. Proc Natl Acad Sci U S A. (2015)
- Carr AC, Maggini S. Vitamin C and Immune Function. Nutrients. (2017)
- Hemilä H. Vitamin C and Infections. Nutrients. (2017)
- Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. (2013)
- Ran L, et al. Extra Dose of Vitamin C Based on a Daily Supplementation Shortens the Common Cold: A Meta-Analysis of 9 Randomized Controlled Trials. Biomed Res Int. (2018)
- Brockman-Schneider RA, Pickles RJ, Gern JE. Effects of vitamin D on airway epithelial cell morphology and rhinovirus replication. PLoS One. (2014)
- Telcian AG, et al. Vitamin D increases the antiviral activity of bronchial epithelial cells in vitro. Antiviral Res. (2017)
- Berry DJ, et al. Vitamin D status has a linear association with seasonal infections and lung function in British adults. Br J Nutr. (2011)
- Rafiq R, et al. Associations of Serum 25(OH)D Concentrations with Lung Function, Airway Inflammation and Common Cold in the General Population. Nutrients. (2018)
- Martineau AR, et al.. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. (2017)
- Aglipay M, et al. Effect of High-Dose vs Standard-Dose Wintertime Vitamin D Supplementation on Viral Upper Respiratory Tract Infections in Young Healthy Children. JAMA. (2017)
- Hemilä H, et al. Zinc acetate lozenges for treating the common cold: an individual patient data meta-analysis. Br J Clin Pharmacol. (2016)
- Hemilä H, Chalker E. The effectiveness of high dose zinc acetate lozenges on various common cold symptoms: a meta-analysis. BMC Fam Pract. (2015)
- Hemilä H. Zinc lozenges and the common cold: a meta-analysis comparing zinc acetate and zinc gluconate, and the role of zinc dosage. JRSM Open. (2017)
- Alexander TH, Davidson TM. Intranasal zinc and anosmia: the zinc-induced anosmia syndrome. Laryngoscope. (2006)
- Shah SA, et al. Evaluation of echinacea for the prevention and treatment of the common cold: a meta-analysis. Lancet Infect Dis. (2007)
- Karsch-Völk M, et al. Echinacea for preventing and treating the common cold. Cochrane Database Syst Rev. (2014)
- Tiralongo E, Wee SS, Lea RA. Elderberry Supplementation Reduces Cold Duration and Symptoms in Air-Travellers: A Randomized, Double-Blind Placebo-Controlled Clinical Trial. Nutrients. (2016)
- Ulbricht C, et al. An evidence-based systematic review of elderberry and elderflower (Sambucus nigra) by the Natural Standard Research Collaboration. J Diet Suppl. (2014)
- Holst L, Havnen GC, Nordeng H. Echinacea and elderberry-should they be used against upper respiratory tract infections during pregnancy?. Front Pharmacol. (2014)
- Fashner J, Ericson K, Werner S. Treatment of the common cold in children and adults. Am Fam Physician. (2012)
- Lizogub VG, Riley DS, Heger M. Efficacy of a pelargonium sidoides preparation in patients with the common cold: a randomized, double blind, placebo-controlled clinical trial. Explore (NY). (2007)
- Meng H, et al. Consumption of Bifidobacterium animalis subsp. lactis BB-12 impacts upper respiratory tract infection and the function of NK and T cells in healthy adults. Mol Nutr Food Res. (2016)
- Braga VL, et al. What do Cochrane systematic reviews say about probiotics as preventive interventions?. Sao Paulo Med J. (2017)
- Wang Y, et al. Probiotics for prevention and treatment of respiratory tract infections in children: A systematic review and meta-analysis of randomized controlled trials. Medicine (Baltimore). (2016)
- Strasser B, et al. Probiotic Supplements Beneficially Affect Tryptophan-Kynurenine Metabolism and Reduce the Incidence of Upper Respiratory Tract Infections in Trained Athletes: A Randomized, Double-Blinded, Placebo-Controlled Trial. Nutrients. (2016)
- Pu F, et al. Yogurt supplemented with probiotics can protect the healthy elderly from respiratory infections: A randomized controlled open-label trial. Clin Interv Aging. (2017)