Exercise-induced bronchoconstriction and the gut microbiome

Exercise-induced Bronchoconstriction

In this Research Spotlight, we introduce exercise-induced bronchoconstriction (EIB), an acute physical response to exercise that involves the narrowing of the airways. Thought to be in part caused by environmental factors such as pollution and air conditions, EIB can lead to uncomfortable chest tightness and wheezing, and as such is of concern to both elite athletes and recreational exercisers.

During exercise, breathing via the mouth typically increases. Whilst this enables more air to be drawn in, air that comes in through the mouth is colder and drier than air that is inhaled through the nose, resulting in moisture being pulled from the airways. This drying of the airways leads to narrowing and irritation, and the subsequent release of inflammatory mediators, in what is referred to as bronchoconstriction.

EIB is common in those with asthma and is a comorbid factor for the conditions, affecting as many as 90% of these individuals (Aggarwal et al., 2018). However, it can occur in up to 20% of individuals without any underlying aetiology, and between 30 and 90% athletes (Atchley and Smith., 2020). However, the true prevalence is not known due to a lack of epidemiological studies differentiating between asthmatics and healthy individuals.

The physical implications of EIB can often have a negative impact on quality of life and prevent individuals from participating in exercise. Individuals with asthma report feelings of frustration and embarrassment, and often avoid exercise-related activities, and as such, demonstrates the importance of managing the condition (Aggarwal et all., 2018).

Management of EIB

Current management strategies for EIB include medications and non-pharmacological strategies such as engaging in a prolonged warm-up to allow the body to prepare for physical activity. Other possible strategies include dietary-related interventions which could target inflammation, such as supplementing with vitamin C and omega-3 polyunsaturated fatty acids, reducing sodium intake and weight management (Koya et al., 2020). However, more evidence is needed to assess the effectiveness of these interventions.

Furthermore, research suggests that modulation of the gut microbiome could influence systemic immune function. Whilst the mechanisms are unclear, it could be due to crosstalk between beneficial commensal microbes, such as bifidobacteria, and the intestinal mucosal immune system which can lead to an immunomodulatory effect (Liu et al., 2022). Probiotics and prebiotics, as nutritional supplements used in athlete and non-athlete populations, have the potential to positively modulate the gut microbiota and enhance its ability to perform functions which could have a positive impact on wellbeing (Liu et al., 2022).

Research using Bimuno® GOS

Bimuno® GOS (B-GOS) is a prebiotic fibre containing galactooligosaccharides that has been scientifically proven to stimulate the growth of bifidobacteria in the gut (Depeint et al., 2008; Grimaldi et al., 2018; Huaman et al., 2018; Silk et al., 2009; Vulevic et al., 2008; Vulevic et al., 2015; Vulevic et al. 2018). In 2016, Williams et al conducted a randomised, cross-over study looking at the effects of B-GOS on hyperpnoea-induced bronchoconstriction (HIB). HIB is often used as a surrogate for EIB in scientific literature as under laboratory conditions it tend to be a simulation of EIB.

A total of 18 participants were recruited. 10 participants with asthma were assigned to the intervention group (vs 8 non-asthmatics in the control group) where they consumed 2.75g active GOS daily for 3 weeks followed by a 2-week wash-out period. The results indicated a 40% attenuation in markers of airway inflammation, such as c-reactive protein, chemokine CC ligand 17 and tumour necrosis factor alpha (Williams et al., 2016), indicating a reduction in the severity of HIB.

Through its impact on the gut microbiome, this research suggests that Bimuno® has the potential to reduce hyper-responsiveness of the airways that is associated with HIB/EIB. The precise mechanisms by which Bimuno® modulates immune function and reduces airway inflammation is unclear and requires further exploration, however, this demonstrates the potential effect of prebiotics, which could be relevant not only in asthmatic populations, but also in recreational exercisers and elite athletes.


Aggarwal, B., Mulgirigama, A. and Berend, N. (2018). Exercise-induced bronchoconstriction: prevalence, pathophysiology, patient impact, diagnosis and management. npj Primary Care Respiratory Medicine, [online] 28(1). Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6092370/.

Atchley, T.J. and Smith, D.M. (2020). Exercise-induced bronchoconstriction in elite or endurance athletes: Annals of Allergy, Asthma & Immunology, [online] 125(1). Available at: https://www.annallergy.org/article/S1081-1206(20)30069-7/fulltext#:~:text=The%20prevalence%20of%20EIB%20is%20estimated%20to%20be,stressors%20to%20the%20airways%20encountered%20during%20intense%20exercise.