FIRE-Diet: Food as an Intervention to Reduce the Effects of Woodsmoke Exposure on Respiratory Health

Overview

Research suggests that consuming more fatty fish, fruits, and vegetables could potentially shield the lungs from the negative impacts of air pollution. The research team will look at whether a dietary intervention aimed at increasing intake of these foods can protect the lungs from woodsmoke as the air pollutant and look into how this works.

Detailed description

This study aims to recruit 48 healthy adult volunteer participants (24 male and 24 female biologic sex assigned at birth) with no known respiratory diseases (as assessed by the study physician) who will breathe in woodsmoke while they are supported to eat a diet higher in fatty fish, fruits, and vegetables (the intervention diet), or not (the control diet).

All participants will undergo a screening visit to assess eligibility for the study. Once deemed eligible, they will experience three exposure visits: one fresh air (filtered air - FA) exposure and two woodsmoke (WS) exposures. The study will span a minimum duration of 15 weeks with 10 in-person visits to the site at Vancouver General Hospital, totaling approximately 34.5 hours. During these visits, participants will complete a series of questionnaires, sample collections (blood, urine, sputum (clumps of mucus that are coughed up from the lungs)), and lung function tests, in addition to the exposures mentioned above.

Off-site commitments will require participants to follow the recommended diet assigned at the time, complete some electronic questionnaires and breathing tests at home after exposures, and complete telephone calls with the study dietician (approximately 30-minute calls, weekly).

Participants will be provided with meal and grocery deliveries to meet intake goals specified by the study or a subsidized amount of groceries per week depending on the diet intervention assigned at that time.

Interventions

• Other Intervention Diet
  Designed to increase Omega-3 Fatty Acids (Eicosapentaenoic acid (EPA), Docosahexaenoic acid (DHA)), fruit, and vegetable intake, participants will receive grocery and meal deliveries for approximately 4-weeks via online ordering with dietician counselling.
• Other Control Diet
  Participants will receive weekly food subsidies for their groceries for 4-weeks (\~equivalent to the subsidies to provide groceries in the Intervention arm) but are free to purchase whatever they wish. The participants will continue to have dietician counseling during this time.

Primary outcome measures

• Within-individual change in sputum neutrophil % [Time frame: Across study duration, anticipated ~15 weeks.]
• Within-individual change in sputum neutrophil activation and function [Time frame: Across study duration, anticipated ~15 weeks]
• Within-individual change in airway resistance [Time frame: Across study duration, anticipated ~15 weeks.]
• Within-individual change in sputum biomarkers of inflammation [Time frame: Across study duration, anticipated ~15 weeks.]

Secondary outcome measures (6)

• Within-individual change in sputum biomarkers/arbiters of inflammation [Time frame: Across study duration, anticipated ~15 weeks.]
• Within-individual change in upper airway (nasal) markers of neutrophil activation and function [Time frame: Across study duration, anticipated ~15 weeks.]
• Within-individual change in upper airway (nasal) biomarkers/arbiters of inflammation [Time frame: Across study duration, anticipated ~15 weeks.]
• Within-individual change in blood neutrophil % [Time frame: Across study duration, anticipated ~15 weeks.]
• Within-individual change in blood neutrophil activation and function [Time frame: Across study duration, anticipated ~15 weeks]
• Within-individual change in spirometry [Time frame: Across study duration, anticipated ~15 weeks.]

Eligibility criteria

Inclusion criteria

• Healthy, and specifically with no respiratory disease
• Not taking any supplements, or willing to abstain from supplement use for 4-weeks prior to study start and the whole duration of the study,
• Must currently consume, on average, less than 2 servings of fish per week and fewer than 5 servings of fruits and vegetables per day based on screening questionnaires.
• Must have a null GSTM1 genotype determined at screening.
• Must be able to provide a sufficient sputum sample during the screening visit.

Exclusion criteria

• Pregnant or planning to become pregnant during the study period.
• Health conditions that would pose an unacceptable risk of dietary change, or conditions that are uncontrolled based on principal investigator's judgement.
• Actively attempting to lose weight.
• Frequent wood smoke exposure (e.g. at home or employment).
• Unable to store provided meals and food safely.
• Food allergies/intolerance or food aversion preventing adherence to the intervention diet, or unwillingness/medically unable to adjust diet in line with the intervention.
• Relocation during the study period to an area which will prevent food delivery.
• History of smoking tobacco, marijuana, or and other substance or vaping within the past 6 months, or having smoked the equivalent of 0.5 pack-years ever.
• Body mass index (BMI) <18.5, as determined during the in-person screening visit.

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: Yes

Study design

Allocation

Randomized

Model

Crossover

Masking

Single blind

Primary purpose

Other

Study locations

Canada · 1 center

• University of British Columbia — Vancouver

Identifiers

NCT: NCT06711614 · H23-03904

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗