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Impact of Probiotics & Other Key Factors on the Common Cold

by Noelle Patno, PhD

Research has demonstrated that probiotics not only help with gastrointestinal (GI) health but they also support immune health. Specifically, meta-analyses have shown that probiotics help reduce the incidence and duration of colds (AKA acute upper respiratory tract infections [URTI]).1-2 The length of the cold may be reduced by almost a day, resulting in less absenteeism from work, school, or day care.3 This can be significant considering that adults experience ~2-4 URTI episodes per year, with an estimated cost of $1.5 billion in medical care; in addition, an estimated 40% lost work time and 30% school absenteeism4 nets ~$40 billion annually.5

Supporting gut and immune health via targeted probiotic supplementation is a wise approach, but certain probiotic strains are more effective than others and have disease-specific effects, as a recent meta-analysis demonstrated.6 Consumption of probiotics in general is associated with an 8% relative risk reduction for URTI infections,2 and a strain-specific study has even investigated whether probiotics can mitigate the impact of the common cold on your lifestyle, particularly keeping up an active lifestyle.7 

A randomized, double-blind, placebo-controlled trial evaluated probiotic supplementation in healthy, active adults for its effect on URTI, GI illness, and physical activity:7

– Population: healthy, physically active Australian adults 18-60 years old (N=465; 48% female) who exercised at least 30 min 3x/week

– Intervention and monitoring phase: 5 months, tracking GI and URTI symptoms. URTI was defined as having 2+ symptoms (scratchy or sore throat, sneezing stuffy nose, runny nose) for 3+ consecutive days. Physical activity was quantified using a web-based questionnaire.

– Supplementation arms:

  • 10 billion colony-forming units (CFUs) of 2 probiotic strains: 5 billion CFU/day of Lactobacillus acidophilus NCFM and 5 billion CFU/day of Bifidobacterium animalis subsp. lactis Bi-07
  • 2 billion CFU/day of Bifidobacterium animalis subsp. lactis Bl-04
  • Placebo


Study findings:7

– Reduction in risk for URTI: ↓27% with Bl-04 and ↓19% (not statistically significant) with NCFM + Bi-07 combo

– Time-to-illness: 3.4 months with NCFM + Bi-07 (0.9 month delay compared to placebo); 3.2 months with Bl-04 (0.7 month delay compared to placebo); 2.5 months using placebo

– Physical activity: Longer duration of physical activity (30 minutes more per week than placebo) in those who consumed NCFM + Bi-07 combo

It is noteworthy that the healthy, physically active adults in this study exercised on average a half hour longer per week when consuming 10 billion NCFM + Bi-07 per day, while this effect was not observed in the Bl-04 group.7 The authors suggest that this increase in physical activity may be due to the delay in the time-to-illness over the course of the 5 months of the study, which theoretically allowed the probiotic consumers to exercise for a significantly longer period of time than people who were randomized to receive the placebo in this trial.7

The NCFM + Bi-07 probiotic combo has previously been shown to reduce fever, coughing, and rhinorrhea duration by 48% (relative to placebo) in children ages 3-5 years, an effect greater and more significant than using NCFM alone. 8 So, how might bacterial supplementation benefit a cold? It is important to remember that viruses (not bacteria) predominantly cause URTIs (e.g. 77% of 425 children tracked over 4 years).11 While bacteria have many different functions in the body, suggested mechanisms for probiotic activity protecting against URTI include:12

  • Preventing pathogen adhesion to the intestine
  • Producing compounds that prevent other bacteria from growing in the intestine
  • Producing beneficial metabolites that promote intestinal health
  • Modulating the immune system

It is possible that the benefits observed in the aforementioned study7 occurred through an immune-stimulating mechanism, which has been studied through immune cell stimulation in various animal models using NCFM,13-15 or immune cell activation with Bi-07 in elderly.16 Another study using 2 billion CFU/day of Bl-04 evaluated response to a rhinovirus challenge in adults and saw no difference in lower respiratory inflammation, infection rate, or subjective symptoms, but did observe a significant reduction in chemokine (C-X-C motif) ligand 8 (CXCL8) response, which is associated with reduced illness symptoms while still being virally infected.10 The number of visits to general practitioners and medication usage for cold or flu, including antibiotics, did not differ significantly between the groups in the Australian RCT described above,7 suggesting that bacterial infection was not significantly different between the groups.

Other considerations for supporting immune health to help prevent or treat the cold: 

  1. Most URTIs are caused by viruses, not bacteria, and consistent with that, antibiotics worsened or did not change the clinical outcome in children with URTI17
  2. Exercise and meditation (with meditation possibly having a stronger effect) may reduce flu and cold and can improve function and quality of life18
  3. Commonly recommended nutraceuticals for immune health maintenance and support:  
    – Zinc supplementation of at least 80 mg/day in meta-analyses shortens colds by about 33%20
    – Vitamin C at 1-2 g/day may modestly reduce duration and severity of the common cold19
    – Echinacea at 2.4-4 g/day may be modestly beneficial19,21
    – Vitamin D3 showed a significant risk reduction in URTI22 (one-daily dosing was most effective), and one trial using 800 IU of vitamin D3 demonstrated shorter duration and severity of URTI, with significant improvement in QOL23
  4. Sleep is believed to be preventive of URTI and promotes good health, with a recent study in military recruits demonstrated that <6 hours of sleep/night increased the risk of URTI by 4x, resulting in subsequent loss of training days24

In addition to getting adequate sleep, staying physically active, meditating, and consuming and supplementing key nutrients to reduce the risk of URTI, taking evidence-based probiotic strains may bolster efforts to reduce the risk of URTI illness. While more than one probiotic strain may be beneficial to reduce such a risk, other benefits may be afforded by particular strains.


  1. Hao Q et al. Probiotics for preventing acute upper respiratory tract infections. Cochrane Database Syst Rev. 2015;(2):CD006895.
  2. Kang E-J et al. The effect of probiotics on prevention of common cold: a meta-analysis of randomized controlled trial studies. Korean J Fam Med. 2013;34(1):2-10.
  3. King S et al. Effectiveness of probiotics on the duration of illness in healthy children and adults who develop common acute respiratory infectious conditions: a systematic review and meta-analysis. Br J Nutr. 2014;112(01):41-54.
  4. Kirkpatrick GL. The common cold. Prim Care. 1996;23(4):657-675.
  5. Fendrick AM et al. The economic burden of non-influena-related viral respiratory tract infection in the United States. Arch Intern Med. 2003;163(4):487-494.
  6. McFarland LV et al. Strain-specificity and disease-specificity of probiotic efficacy: a systematic review and meta-analysis. Frontiers in Medicine. 2018;5:124.
  7. West NP et al. Probiotic supplementation for respiratory and gastrointestinal illness symptoms in healthy physically active individuals. Clinical Nutrition. 2014;33(4):581-587.
  8. Leyer GJ et al. Probiotic effects on cold and influenza-like symptom incidence and duration in children. Pediatrics. 2009; 124(2):e172-e179.
  9. Paineau D et al. Effects of seven potential probiotic strains on specific immune responses in healthy adults: a double-blind, randomized, controlled trial. FEMS Immunol Med Microbiol. 2008;53(1):107-113.
  10. Turner RB et al. Effect of probiotic on innate inflammatory response and viral shedding in experimental rhinovirus infection – a randomized controlled trial. Benef Microbes. 2017;8(2):207-215.
  11. Harnden A et al. Respiratory infections for which general practitioners consider prescribing an antibiotic: a prospective study. Arch Dis Child. 2007;92(7):594-597.
  12. Bermudez-Brito M et al. Probiotic mechanisms of action. Ann Nutr Metab. 2012;61(2):160-174..
  13. Foligne B et al. Correlation between in vitro and in vivo immunomodulatory properties of lactic acid bacteria. World J Gastroenterol. 2007;13(2):236-243.
  14. Foligne B et al. A key role of dendritic cells in probiotic functionality. PLoS ONE. 2007;2(3):e313.
  15. Zeuthen LH et al. Lactobacillus acidophilus induces a slow but more sustained chemokine and cytokine response in naïve foetal enterocytes compared to commensal Escherichia coli. BMC Immunol. 2010;11:2.
  16. Maneerat S et al. Consumption of Bifidobacterium lactis Bi-07 by healthy elderly adults enhances phagocytic activity of monocytes and granulocytes. J Nutr Sci. 2013;2:e44.
  17. Fahey T et al. Systematic review of the treatment of upper respiratory tract infection. Arch Dis Child. 1998;79(3):225-230.
  18. Obasi CN et al. Advantage of meditation over exercise in reducing cold and flu illness is related to improved function and quality of life. Influenza Other Respir Viruses. 2013;7(6):938-944.
  19. Rondanelli M et al. Self-care for common colds: the pivotal role of vitamin D, vitamin C, zinc, and Echinacea in three main immune interactive clusters (physical barriers, innate and adaptive immunity) involved during an episode of common colds- practical advice on dosages and on the time to take these nutrients/botanicals in order to prevent or treat common colds. Evid Based Complement Alternat Med. 2018;2018:5813095.
  20. 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;8(5):2054270417694291.
  21. Karsch-Völk M et al. Echinacea for preventing and treating the common cold. Cochrane Database Syst Rev. 2014;2:CD000530.
  22. Bergman P et al. Vitamin D and respiratory tract infections: a systematic review and meta-analysis of randomized controlled trials. PLoS ONE. 2013;8(6):e65835.
  23. Shimizu Y et al. Intake of 25-hydroxyvitamin D3 reduces duration and severity of upper respiratory tract infection: a randomized, double-blind, placebo-controlled, parallel group comparison study. J Nutr Health Aging. 2018;22(4):491-500.
  24. Wentz LM et al. Increased risk of upper respiratory infection in military recruits who report sleeping less than 6 h per night. Mil Med. May 2018. [Epub ahead of print]


Noelle Patno, PhD received her PhD in Molecular Metabolism and Nutrition and Masters in Translational Science from the University of Chicago, studying the role of microbial components in intestinal epithelial cell survival related to inflammatory bowel disease. Prior to her graduate studies, Dr. Patno received a chemical engineering degree from Stanford University and worked as an engineer. She has personal experience and interest in preventive nutrition and nutritional therapies for chronic disease, and her current role involves researching and developing probiotics, prebiotics, and other nutritional programs for the promotion of digestive and overall health.

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