Dr. Dwayne Jackson

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A supplement a day, keeps colds at bay

Dwayne N. Jackson, PhD

Intense high volume training increases the risk of developing minor upper respiratory illness (a.k.a. the common cold). Most often caused by viral infections, colds in themselves are not considered life threatening to young healthy people.  However, for an athlete, catching a cold can lead to poor athletic/exercise performance, missed training sessions, and/or require forfeit from competition. 


In this article we give you the low down on 3 supplements that have been proven to decrease your chances of catching a cold— keeping you in the gym and out of bed.    



What is it? An antioxidant flavonoid found in fruits, vegetables, and grains. Quercetin has been shown to have potent anti-viral properties and has been reported to boost immunity via upregulation of interferon gamma (IFNγ). 

What does the research say? A study published in Medicine and Science in Sports and Exercise illustrated that taking quercetin (1000 mg daily for 3 weeks) reduced upper respiratory illness in the 2 weeks following a 3-day period of exhaustive exercise in cyclists. Most interestingly, none of the measured markers of immunity, inflammation, and oxidative stress were improved in this study, suggesting that quercetin exerts may promote direct antiviral effects. In support, a randomized clinical trial, published in Pharmacological Research, reported that physically active middle-aged people who took 1000 mg of quercetin daily (for 12 weeks) had decreased occurrence of colds.  

Dose: Based on these studies, take 1000 mg of quercetin daily, split into two doses. Take one 500 mg dose upon waking and another 500 mg in the late afternoon. 



Nieman DC, Henson DA, Gross SJ, Jenkins DP, Davis JM, Murohy EA et al. Quercetin reduces illness but not immune perturbations after intensive exercise. Med Sci Sports Exerc 2007; 39: 1561–1569.


Heinz SA, Henson DA, Austin MD, Jin F, Nieman DC. Quercetin supplementation and upper respiratory tract infection: a randomized community clinical trial. Pharmacol Res 2010; 62: 237–242.



What are they? Live microorganisms (i.e., bacteria and yeast) that, when taken consistently in adequate doses, have health promoting effects. Probiotics increase number of “good bacteria” in our gut and promote overall immunity.

What does the research say? Many well-controlled studies in athletes show that daily probiotic supplementation results in fewer colds and lower severity of cold symptoms. A relatively recent meta-analysis, published in The Cochrane Database for Systematic Reviews, analyzed data from randomized control trials involving probiotic supplementation as a preventative measure for colds in athletes and non-athletes.  This large-scaled study (3451 subjects) concluded that daily probiotic supplementation reduced the incidence of colds. Furthermore, probiotics supplements may reduce the risk of gastrointestinal infection—which is a common issue when travelling. 

Dose: Based on the research, use probiotics that contain Lactobacillus and Bifidobacterium—at a daily dose of approximately 10 billion live bacteria.



Cox AJ, Pyne DB, Saunders PU, Fricker PA. Oral administration of the probiotic Lactobacillus fermentum VRI-003 and mucosal immunity in endurance athletes. Br J Sports Med 2010; 44: 222–226.


Gleeson M, Bishop NC, Oliveira M, Tauler PJ. Daily probiotic’s (Lactobacillus casei Shirota) reduction of infection incidence in athletes. Int J Sport Nutr Exerc Metab 2011; 21: 55–64. 


West NP, Pyne DB, Cripps AW, Hopkins WG, Eskesen DC, Jairath A et al. Lactobacillus fermentum (PCC(R)) supplementation and gastrointestinal and respiratory-tract illness symptoms: a randomised control trial in athletes. Nutr J 2011; 10: 30. 


Haywood BA, Black KE, Baker D, McGarvey J, Healey P, Brown RC. Probiotic supplementation reduces the duration and incidence of infections but not severity in elite rugby players. J Sci Med Sport 2014; 17: 356–360.


Gleeson MProbiotics. In: Castell LM, Stear S, Burke LM (eds). Nutritional Supplements in Sport, Exercise and Health: An A-Z Guide. Routledge: Abingdon, UK. 2015 pp 214–215.


West NP, Horn PL, Pyne DB, Gebski VJ, Lahtinen SJ, Fricker PA et al. Probiotic supplementation for respiratory and gastrointestinal illness symptoms in healthy physically active individuals. Clin Nutr 2014; 33: 581–587. 


Pyne DB, West NP, Cox AJ, Cripps AW. Probiotics supplementation for athletes – clinical and physiological effects. Eur J Sport Sci 2015; 15: 63–72. 


Hao Q, Lu Z, Dong BR, Huang CQ, Wu T. Probiotics for preventing acute upper respiratory tract infections. Cochrane Database Syst Rev 2011; 9: CD006895.


Vitamin D3  

What is it? A bioavailable and potent oral form of vitamin D. Generally less than 20% of the body’s vitamin D needs come from the diet; however, during sun exposure, we get a good shot of vitamin D from the conversion of 7-dehydrocholesterol in the skin. Notably, many people limit exposure to the sun’s damaging UV radiation and, as such, tend to be vitamin D deficient—especially during winter months. Beyond being essential for calcium metabolism/absorption, recent research suggests that vitamin D plays a pivotal role in the regulation of immune responses. 

What does the research say? In terms of immunity, vitamin D promotes the production of antimicrobial proteins and immune factors. Low vitamin D status in athletes is associated with low saliva IgA secretion (an antibody that plays a critical role in mucosal immunity) and increased risk of respiratory infections. Several studies have reported that vitamin D3 supplements reduce the number of common cold episodes and reduce the use of antibiotics. 

Dose: Vitamin D3 dosing at ~4000 IU per day (with or without food) has been shown to recover vitamin D status to normal levels within a matter of weeks and significantly elevates saliva IgA and antimicrobial secretion rates in athletes. 



Gleeson M. Immunological aspects of sport nutrition. Immunol Cell Biol. 2015 Dec 22. [Epub ahead of print]


 de Sa Del Fiol F, Barberatp-Filho S, Lopes LC, de Cassia Bergamaschi C. Vitamin D and respiratory infections. J Infect Dev Ctries 2015; 9: 355–361.

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