Soluble fibre for asthma control

INTERVENTION: This study is a double‐blind, randomised, placebo‐controlled, 4‐way crossover trial including clinically stable asthmatic adults to examine the effect of a soluble fibre supplement (an oligosaccharide blend) on asthma control and airway inflammation. There are three intervention arms and one placebo arm in this study. Each subject will be randomly allocated to take each treatment/placebo arm in random order for 2 weeks each, with a 2 week wash out period in between each phase of the study. 1. High dose formulation 1: 12 g/d of total oligosaccharides via (1x6g oligosaccharides and 1x6g placebo) dose in morning and (1x6g oligosaccharides) dose in evening. 2. High dose formulation 2: 12g total oligosaccharides via 1x12g oligosaccharides dose in morning and 1x6g placebo dose in evening. 3. Low dose formulation: 1x6g total oligosaccharides via (1x6g oligosaccharides and 1x6g placebo) in morning and 1x6g dose placebo dose in evening. 4. Placebo control: 18 g/d or equivalent weight to investigational product of maltodextrin powder via 1x12g dose in morning and 1x6g dose in evening. The oligosaccharide blend powder and placebo powder (maltodextrin) will be provided to participants in individual sachets for each dose, to be mixed with water twice daily (morning/evening). This study takes place over 16 weeks. Two weeks prior to the start of the study, and for the duration of the study, participants will consume a fibre controlled diet. This will include consumption of no more than 2 serves of fruits and vegetables per day and consume ½ cup of bran‐based cereal per day to avoid constipation, and avoidance of other fibre‐rich foods including oats, oat bran, beans, seeds and sources of probiotics such as yoghurt and fermented milk drinks. Participants will be provided with a standardized evening meal (pasta meal), which they will be asked to consume the night before each of their scheduled appointments. They will also be asked to fast for 12‐hours prior to the clinic visit. Adherence with the protocol will be monitored by sachet returns and study diaries. CONDITION: Asthma PRIMARY OUTCOME: Asthma Control as measured by the Juniper Asthma Control Questionnaire (ACQ7) SECONDARY OUTCOME: Airway hyper‐responsiveness determined by saline challenge. Airway inflammation as measured by exhaled nitric oxide (eNO). Airway inflammation as measured by sputum cell counts. Faecal microbiota ‐ exploratory analysis Gastrointestinal symptoms as assessed by the Gastrointestinal Symptoms Rating Scale scores (GSRS) (modified). General Quality of life as measured by the 36‐Item Short Form Survey Instrument (SF‐36) Lung function as measured by spirometry (FEV1 and FVC). Plasma short chain fatty acids (SCFA) as measured by gas chromatography. Quality of Life assessed by the Asthma Quality of Life Questionnaire (AQLQ) INCLUSION CRITERIA: Males and females aged 18 years and over. Doctor diagnosis of asthma and confirmed airway hyper‐responsiveness Poorly controlled asthma, defined as ACQ6 >0.75 units