The current study aims to explore the role of prebiotic supplementation in adults with and without Asthma/Exercise-Induced Bronchoconstriction (A/EIB). All participants will be asked to consume a prebiotic supplement, and a placebo, each for a total duration of four weeks, separated by a two-week wash out period. The investigators hypothesise that improvements in pulmonary function observed in adults with Asthma following prebiotic supplementation. We hypothesise that improvements in pulmonary function will be attributed, at least in part, to gut microbiota mediated improvements in human immune function.

The current study will investigate the effects of prebiotic supplementation on airway inflammation/bronchoconstriction in adults diagnosed with Asthma/Exercise-Induced Bronchoconstriction (A/EIB). Previous research conducted in adults diagnosed with A/EIB has reported significant improvements in pulmonary function following three weeks of prebiotic supplementation. The significant improvements in pulmonary function were attributed to an attenuation of various markers of airway inflammation, potentially regulated by gut microbiota mediated improvements in systemic immune function.

Prebiotics are a type of non-digestible carbohydrate/dietary fibre that can only be digested by certain beneficial bacteria. During the fermentation of prebiotics, beneficial bacteria produce energy/metabolites that can be used to support a variety of human immune functions, such as reducing the level of airway inflammation that occurs following exposure to relevant triggers (e.g. exercise).

Imbalances and/or deficiencies in gut bacterial composition/metabolic activity have been identified in children/adults diagnosed asthma. However, the potential mechanisms behind prebiotic mediated improvements in the severity of asthma have yet to be investigated.

Participants with and without A/EIB will be allocated two separate nutritional supplements following a double-blind, placebo-controlled design. During the first phase of the nutritional intervention, participants will consume the first supplement (either prebiotic or placebo), for a total duration of four weeks. A two-week wash out period will then be completed before the remaining nutritional supplement is administered for an equal duration.

Analyses of key human/bacterial metabolite concentrations will be carried out alongside assessments of immune and pulmonary function, and intestinal permeability at baseline, and throughout all phases of the nutritional intervention. Current understandings of the role of the gut microbiota in the pathogenesis of A/EIB will be expanded through the investigation of novel pathophysiological mechanisms, helping to inform future therapeutic prospects for asthma.

Inclusion Criteria:

Be 18-50 years of age at the date of your first visit.

Have a body mass index (BMI) of 18.5-25 kg∙m2 (this will be worked out by the researchers using the participant's height and body weight).

Be physically active (completing 3 or more exercise sessions a week lasting at least 45 minutes each).

Be a non-smoker.

Asthma is defined as Steps 1, 2, or 3 based on British Thoracic Society guidelines.

Asthma sufferers must have a current medication prescription from their GP (e.g. maintenance/reliever inhalers).

In the researcher's opinion, the participant is able and willing to follow all trial requirements.

Exclusion Criteria

Asthma defined as Steps 4 or 5 based on British Thoracic Society guidelines.

Asthma sufferers who do not have a current medication prescription from their GP (e.g. maintenance and reliever inhalers).

Regular consumption of Omega-3 supplements, and/or high levels of Omega-3 intake from food (e.g. consuming more than 1-2 portions of oily fish such as salmon or mackerel a week).

Regularly consume antioxidant supplements.

Standard multivitamin and mineral supplements are acceptable, as long as the product label states the recommended Dietary Reference Values (DRV's).

If a single antioxidant supplement (e.g. Vitamin C), exceeds the recommended daily DRV's this will be checked with the chief investigator.

Take a daily dose of aspirin or other non-steroidal anti-inflammatory drugs such as ibuprofen.

Have consumed prebiotics and/or probiotics, drugs that affect gastrointestinal mobility, or laxatives in the 4 weeks before participation.

Currently taking a daily dose of anti-histamine, which could not be refrained from for 72 hours before each testing session.

Unable to refrain from taking Asthma medication (e.g. maintenance and reliever inhalers) for a prescribed duration before each testing session (e.g. 8-96 hours).

Vegetarian or vegan diet.

Previously diagnosed with chronic obstructive pulmonary disease (COPD), emphysema, chronic bronchitis, or similar respiratory illness.

Participants with asthma that have ever been hospitalised due to asthma (e.g. intensive care unit).

Participants with asthma that have received treatment with oral corticosteroids/been admitted to hospital during the past 12 months for their asthma.

An increase/step-up in asthma medication during the study (e.g. moving from Step 1 to Step 2, Step 2 to Step 3 etc.).

Participants with asthma who do not obtain an additional prescription for a reliever inhaler to be stored securely at NTU if needed during visits. Additional prescriptions must be obtained before familiarisation/visit two. Participants will be reimbursed for the cost of additional reliever inhaler prescriptions.

History of heart failure, pulmonary hypertension, embolism, or other pulmonary heart disease.

History of recurrent chest infections.

Smoker.

Pregnant, planning pregnancy or lactating.

Had an acute infection in the last four weeks, and/or major operation in the past four months.

History of gastrointestinal drug reaction.

Have taken antibiotics in the past 3 months.

History or current evidence of gastrointestinal disease (e.g. chronic constipation, diarrhoea, irritable bowel syndrome, Chrohn's disease).

Have recently taken part in other research projects. Participants will be asked to notify the chief investigator.

Participants are, or believe that they are lactose intolerant.

Individual participant data may be made available to other researchers following completion of the current trial in an anonymised/pseudonymised format to prevent individual participant identification. Data will be provided in response to certain requests (e.g. if a systematic review and meta-analysis/statistical power calculation is being conducted that requires access to certain raw data).

Only the company providing the nutritional supplements (HOST Therabiomics) will be aware of the supplement blinding protocol.

Upon trial completion (e.g. the final visit of the final participant), the chief investigator will contact HOST Therabiomics to obtain information on the supplement blinding protocol. Should any participants, care providers, investigators, or outcome assessors become aware of the blinding protocol during the trial they will be informed not to disclose this information to any other relevant personnel. Participants who become aware of the blinding protocol during participation would be withdrawn from the trial.