Can Astaxanthin Help Manage Asthma in POlluted Areas?

Inclusion Criteria: * Adults 18+ y * Confirmed clinical diagnosis of mild-to-moderate asthma, defined as: * A physician diagnosed asthma condition consistent with BTS/NICE/SIGN (2024) * Asthma managed at GINA (2024) step 1-3 therapy level, with stable maintenance treatment for ≥4 weeks prior to enrolment * No asthma exacerbation requiring systemic corticosteroids within the preceding 6-8 weeks (those with suspected Asthma will be invited to a familiarisation and eligibility session where they will have clinical investigations to assess for asthma and thus be included or excluded) * Ability to demonstrate acceptable and repeatable spirometry in accordance with ATS/ERS standards * Willing to refrain from antioxidant and anti-inflammatory supplementation (e.g. Omega-3, turmeric, NSAID supplements) for the duration of the study * Not consuming high dietary ASTX sources (e.g., frequent salmonid or crustacean intake), assessed at screening * non-smoking and non-vaping * Able and willing to take daily study capsules and attend all required visits * Able and willing to complete home monitoring, including peak flow, air-quality monitoring, and questionnaires * Able to provide written informed consent Exclusion Criteria: * Current smokers or vapers which is associated with chronic airway remodelling, reduce hyperresponsiveness to bronchodilators, and increased neutrophilic inflammation, which can obscure the true effects of asthma-target interventions * Respiratory tract infection within the preceding 4 weeks * Pregnant or lactating individuals * Presence of significant co-morbidities, including CVD or autoimmune or systemic inflammatory diseases * Renal or gastrointestinal disorders that may affect astaxanthin absorption and metabolism * Known allergy or hypersensitivity to ASTX or any components of the study supplement * History of current evidence of alcohol or substance abuse * Participation in another interventional drug or supplement study within the preceding 3 months * Use of medicines with a narrow therapeutic index where supplement interactions may pose risk (e.g., ciclosporin/tacrolimus, warfarin), assessed by investigator * Other significant chronic respiratory disease (e.g., COPD, bronchiectasis)