Probiotics - Are They Effective in Supporting the Immune System and Reducing "Day Care Syndrome?"

By Dr Megan Yap - PaediatricianGeneral13 Jan 2019

I have taken recent inspiration from you guys, and am trying to blog about topics that you have all suggested to me and today, the first of these:  are probiotics effective in supporting/boosting the immune system?

When my now almost-6-year-old daughter first started day care at the age of 14 months, the scourge of respiratory viruses/bacterial infections was OPPRESSIVE for at least the first 9 months of her attendance.  To this day, my husband Troy is completely paranoid about hand washing hygiene for fear that the whole house be taken down again by some darstardly disease causing microbe – to the point that the kids (aged 3 and 5 years, along with grandparents or other family or friends in the room) will literally roll their eyes when he barks at them to “Wash [their] hands” or “use the alcohol rub!”  So when I posted on the blog’s FB page  a few weeks ago, looking for inspiration for topics, it came as no surprise that a few blog followers requested “Ways to combat day-care syndrome” and how to support their children’s immune system on starting day care.

I give my kids probiotics.  The ones I am currently using are the Inner Health Immune Booster for Kids powder, and a Nature’s Way chewy gummy probiotic.  I feel like the powder probiotic made a difference to both kids… I am less convinced with the gummy.  This is completely opinion and “gut feeling” (sorry, pun intended).  It does however, make ME feel better in that I am doing SOMETHING to help my kids fight colds and flu.

I could not find any specific evidence about these products particularly, and the literature would never talk about specific brands (which are all a mix of different probiotic bacteria), but many different strains of probiotics.  The significance of this is that the evidence I will report to you below may not necessarily pertain to the preparation that you are using.  I could theoretically tabulate all the data on specific strains of probiotic bacteria… but realistically, I don’t have time to do that – sorry! So instead, the summarised information below should be taken as general information on probiotics.

When looking at how probiotics effect immunity, there are actually several different facets to the question that come up in the literature.

  1. Are probiotics effective in reducing the frequency of colds and infections in children?
  2. What effects do probiotics have on the immune system?
  3. Do probiotics have beneficial effects on immune system related disorders like asthma, eczema, allergic rhinoconjunctivitis (hayfever), types 1 and 2 diabetes mellitus and other infections including urinary tract infections and critical illness (eg ventilator assisted pneumonia)?

I could go into the details of how I did my literature search… but that would be sooo boring, and “Ain’t nobody got time for that!!” SO here are the important bits….

  1.  A Cochrane systematic review[i] summarised the evidence for the first question:   Are probiotics effective in reducing the frequency of colds and infections in children?
  • The evidence shows that probiotics DO reduce the number of participations in trials experiencing episodes of acute upper respiratory tract infection by about 47%
  • Probiotics were shown to reduce the duration of an acute URTI by almost 2 days
  • Probiotics may slightly reduce antibiotic use and cold-related school absences

The evidence that exists to support these findings is LOW mainly due to poorly conducted trials (eg poor methods like unclear blinding or randomisation, small sample sizes) and some trials were backed by the manufacturers of the tested probiotics.

A more recent trial involving 136 subjects receiving probiotic drinks of 3 types vs placebo demonstrated that probiotics were safe and effective in fighting & reducing the incidence of the common cold and influenza-like infections by boosting the immune system.[ii]

2.  Probiotic effects on the immune system

Probiotics have many different effects on the immune system… a lot of the physiological pathways though are complicated and difficult to explain in a plain-language way that is meaningful to the average person – but I’ll try.  Essentially, they exert their effect by regulating the balance between special substances secreted by immune system cells called cytokines that cause or reduce inflammation.[iii]  In this way probiotics can normalise dysfunction of the gut mucosa and dampen down allergic (hypersensitivity) reactions.[ii]  Also, establishing a normal bacterial population in the gut can prevent the overgrowth of potential disease-causing strains of bacteria in the gastrointestinal tract.

3. Do probiotics have beneficial effects on immune system related disorders 

Probiotics have been shown to have beneficial effects on extraintestinal disorders, such as atopic eczema, food allergies, hayfever, asthma, critical illnesses, urinary tract infections and even type 1 and 2 diabetes.[iv],[v],[vi]

Obviously there are beneficial effects demonstrated in certain gut-related conditions too like acute gastroenteritis, antibiotic-associated diarrhoea, Clostridium difficile (a bug that can become problematic when one has had normal gut flora wiped out by antibiotics), necrotising enterocolitis, inflammatory bowel disease, irritable bowel syndrome, infantile colic (specifically lactobacillus reuteri), Helicobacter pylori (the bug that causes stomach ulcers), and constipation.[iii],[vii],[viii]


So the answer basically at the end of all of this is probiotics do work to reduce the incidence and severity of common infections, but more studies are probably needed to improve the strength of the evidence.

Further uncertain variables include:

  • Which strains are the most effective (this affects product choice because different preparations have different strains of bacteria)
  • Which dosage forms carry the most live/effective probiotic – eg gummy-chews, powder, drinks, capsules etc (I have heard that the formulation of some dosage forms requires heating of the product hence the processing effectively kills the good bacteria)

Those questions however, would only be answered by more searching of the literature, which I don’t have time to do today.

In Australia… I cannot in fairness however, tell you (backed by evidence) which preparations are the most effective (or not). My favourites though are the Bioceuticals “Baby-biotic” for the littlest littlies (the evidence is actually for another product that can be obtained in hospitals for prem babies, but not available to the general public) and the Inner Health Immune Booster powder for kids.


Well that’s it for today folks, but will come back with another blog about the evidence for other products marketed and commonly used to support immune function (like garlic, horseradish, echinacea, vitamin C, etc etc etc).

Catch you next week!!

Until then, stay well!!


xxDr Megs



[i] Hao QK, Dong BR, Wu TX.  Probiotics for preventing acute upper respiratory tract infection. Cochrane Database of Systematic Reviews. Issue 9, Sept 2011. URL  Accessed on 5/1/2019.

[ii] Zhang H, Yeh C, Jin Z, et al. Prospective study of probiotic supplementation results in immune stimulation and improvement of upper respiratory infection rate. Synth Systems Biotech. 2018;3:113-120.

[iii] Isolauri E, Sutas Y, Kankaanpaa P, Arvilommi H, et al. Probiotics: effects on immunity.  Am J Clin Nutr. 2001;73(suppl):444S-50S.

[iv] Islam SU. Clinical uses of probiotics. Medicine (Baltimore). 2016;95:E2658.

[v] Gulden E, Wong FS, Wen L. The gut microbiota and type 1 diabetes. Clin Immunol. 2015;159:143-153.

[vi] Kecheng Y, Zeng L, He Q, et al. Effect of probiotics on glucose and lipid metabolism in type 2 diabetes mellitus: a meta-analysis of 12 randomised controlled trials. Med Schi Monti. 2017;23:3044-3053.

[vii] Zhang MM, Qian W, Qin YY, et al. Probiotics in Helicobacter pylori eradication therapy: a systematic review and meta-analysis. World J Gastroenterol. 2015;21:4345-4357.

[viii] Patel RM, Underwood MA. Probiotics and necrotising enterocolitis.  Semin Pediatr Surg. 2018;27:39-46.


For more articles from Dr Megan Yap visit her blog – “Dr Megs – Paeds & Feeds” at


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