INL Articles - Probiotics and Upper Respiratory Infections
The role that the gut and probiotics play in immunity and the prevention of upper respiratory tract infections
Welcome to another edition of the INL newsletter. You may have noticed that with the current global landscape we are increasing our newsletter communications. Our aim is to try and share our knowledge with our practitioner network on different applications for immunity as much as we can in this time of increased demand. We hope you're finding them useful for your practice!
In this edition we are going to be looking at some of the key studies done on the role that probiotics can play in the prevention of upper respiratory tract infections along with some of the special conditions that would make them more or less indicated for the different considerations in immunity.
First though, let’s look at why the digestion is such an important consideration in the immune system.
The role of the gut in immunity and the importance of T-Reg cells in inflammation
The gastrointestinal system harbours the largest proportion of the immune system in the body, with over 70% of the total immune system located in this area.(1) This key region is often referred to as the gut-associated lymphatic tissue or GALT.
Within the GALT, intestinal macrophages induce T-reg cells, reducing inflammation in the process. Following their activation in the intestine, T-reg cells then travel into the systemic circulation where they proliferate and are subsequently recruited to inflamed sites around the body.
T-reg immune cells are an important component of immune homeostasis. They can suppress both innate and adaptive immune responses mainly via the anti-inflammatory effects of IL-10 and transforming growth-factor B (TGF-B), consequently down regulating inflammation and the severity of symptoms associated with the induction of Th-1 immune cells by bacteria and viruses.
What kind of role can specific strains of probiotics play in immunity?
Interested in the specific strains and the work they do in the immune system? Well to make it easier we’ve put together an easy to read list of some of the main strains along side their mechanism of action in either the innate or adaptive immune system to help define just exactly how they can help.
- Lactobacillus paracasei has been shown to induce innate immune functions, including increased phagocytosis and increased levels of NK cells, which may account for its benefits in the prevention of cold and flu.(4)
- In adaptive immunity Lactobacillus paracasei and Lactobacillus planetarium have also been shown to strongly stimulate macrophages to produce high levels of interleukin IL-12, a cytokine know to promote Th-1 mediated antiviral immune responses through the production of IFN-y from T-cells and NK cells. (5),(6)
- Lactobacillus rhamnosus (GG) has demonstrated the ability to enhance a variety of immune responses. Administration of LGG has been associated with an increase in numbers of TGF-B secreting T-reg cells in lymph nodes as well as nearly a 2 fold up-regulation of Foxp3 (Forkhead box P3) expressing cells in lymph nodes.(7) Foxp3 is one of the major factors that determines natural T-reg cell development.
- An interesting animal study has also shown that LGG augments NK activity in the respiratory system, indicating potential protection from influenza virus infection.(8) This was corroborated by a more recent study demonstrating that LGG had an up regulating effecting on the pulmonary mRNA expression of genes encoding IFN-y, thus acting as a potent immune stimulant in the fight against viral infection.(9)
Cochrane review involving 3720 people shows probiotic better than placebo for acute upper respiratory tract infections (URTI) by about 47%
In 2015, the landmark Cochrane review on probiotics delivered a foundational finding for the use of probiotics in the treatment of acute URTIs. Looking at 12 high class studies involving children, adults and seniors the review expressed that probiotics were found to be better than placebo in reducing the number of participants experiencing episodes of actor URTI by about 47% (10). This amazing result came in tandem with a reduction in the duration of the acute episodes by about 1.89 days.
A further meta-analysis looking into probiotics specifically in children reproduced these results by showing that probiotic administration appears to be a practical way to decrease the incidence of respiratory tract infections in children. (11)
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