Can Astaxanthin Help Manage Asthma in POlluted Areas?

This study will test whether astaxanthin, a naturally occurring antioxidant supplement, can improve lung function, reduce airway inflammation, and improve asthma control in adults with mild-to-moderate asthma. Participants will receive astaxanthin and placebo in random order in a double-blind crossover design. Each treatment period lasts 4 weeks and is separated by a 3-week washout period. The study also measures indoor and personal air pollution exposure to examine whether pollution influences asthma symptoms, airway responsiveness, and response to treatment. Exploratory thoracic bioelectrical impedance spectroscopy will be assessed alongside standard respiratory tests.

• : * 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

Use the source registry for the full inclusion and exclusion criteria before discussing referral or enrolment.