Vegan Diet and Immune-Inflammatory Outcomes in Asthma and Healthy Adults (VEGASTHMA)

The Effect of a Vegan Diet on Inflammatory and Immune Biomarkers in Adult Patients With Asthma and in Healthy Individuals: A Randomized Controlled Trial

This randomized controlled study evaluates the effects of a balanced vegan diet compared with a balanced omnivorous diet on inflammatory and immune response markers and clinical asthma parameters in healthy adults and individuals with mild to moderate asthma, aged 18 to 50. Participants will follow assigned dietary plans for 12 weeks with dietitian support delivered via digital tools.

Study Overview

• Status: Not yet recruiting
• Conditions: Asthma; Dietary Intervention; Vegan Diet
• Intervention / Treatment: Behavioral: Omnivorous diet; Behavioral: Vegan diet

Detailed Description

This prospective, randomized, controlled study aims to evaluate the effects of a balanced vegan diet on inflammatory and immune response markers, clinical asthma parameters, and metabolic profile in healthy adults and patients with mild to moderate asthma. The study will enroll participants aged 18 to 50 years, who will be randomly assigned to either a vegan diet intervention group or a control group following an omnivorous diet for 12 weeks.

Dietary interventions will be individually tailored by a clinical dietitian according to current national nutrition guidelines. To ensure safety and standardization, all participants will receive vitamin D supplementation (2000 IU/day), and participants in the vegan group will additionally receive vitamin B₁₂ supplementation (25-100 µg/day or weekly equivalent). Adherence to the diet will be monitored through weekly online consultations, 3-day food diaries, and digital tools.

Assessments will be performed at baseline and after 12 weeks of intervention. Evaluated parameters will include:

• Inflammatory markers: hsCRP, IL-4, IL-5, IL-13, TNF-α
• Immune function markers: lymphocyte subpopulations (CD4+, CD8+, CD4+/CD8+ ratio, Treg cells by flow cytometry/ELISA) and immunoglobulins (IgE, IgA, IgG, IgG1-IgG4)
• Respiratory function: fractional exhaled nitric oxide (FeNO), spirometry
• Anthropometric and body composition measures: body weight, body mass index (BMI), waist circumference, waist-to-hip ratio, bioimpedance body composition analysis
• Lipid profile: total cholesterol, HDL, LDL, non-HDL cholesterol, triglycerides
• Asthma symptom control: Asthma Control Test (ACT) scores The planned sample size is 280 participants, distributed across four groups (n=70 per group): healthy - omnivorous diet, healthy - vegan diet, asthma - omnivorous diet, asthma - vegan diet. However, an initial pilot phase will be conducted to assess feasibility and refine study procedures before full-scale recruitment.

• Study Type: Interventional
• Enrollment (Estimated): 280
• Phase: Not Applicable

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

For all groups:

• Aged 18-30 years
• Willing to adhere to assigned dietary plan (vegan or omnivorous) for 12 weeks
• Non-smoker for at least 5 years
• Body mass index (BMI) between 18.5 and 24.9 kg/m2

For the asthma group:

• Clinical diagnosis of mild or moderate asthma (GINA criteria), made at least 12 months before enrollment
• Stable asthma status (no exacerbations or changes in therapy within the past 3 months)
• No change in pharmacotherapy during the study period

Exclusion Criteria:

• Use of systemic corticosteroids (oral or intravenous) within the past 3 months
• Ongoing biological therapy for asthma (e.g., anti-IgE, anti-IL-5, anti-IL-4R)
• Severe asthma as per GINA criteria
• Recent asthma exacerbation requiring hospitalization or steroid burst (<3 months)
• Presence of other chronic autoimmune or inflammatory diseases
• Pregnancy or lactation
• Active infection or acute illness at the time of recruitment
• Adherence to specialized exclusion diets (e.g., ketogenic, low-FODMAP)
• History of eating disorders
• Inability or unwillingness to participate in follow-up visits or comply with the protocol

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Omnivorous diet, healthy individuals	Behavioral: Omnivorous diet; Participants will follow an individually planned, nutritionally adequate, isocaloric omnivorous diet for 12 weeks. Diet plans will be prepared by a clinical dietitian. Adherence will be monitored 3-day food diaries, weekly remote consultations, and digital tools. Participants will receive vitamin D supplementation (2000 IU/day).
Experimental: Vegan diet, healthy individuals	Behavioral: Vegan diet; Participants will follow an individually planned, nutritionally adequate isocaloric vegan diet for 12 weeks. Diet plans will be prepared by a clinical dietitian. Adherence will be monitored 3-day food diaries, weekly remote consultations, and digital tools. Participants will receive vitamin D supplementation (2000 IU/day) and vitamin B12 supplementation according to standard recommendations.
Active Comparator: Omnivorous diet, asthmatic individuals	Behavioral: Omnivorous diet; Participants will follow an individually planned, nutritionally adequate, isocaloric omnivorous diet for 12 weeks. Diet plans will be prepared by a clinical dietitian. Adherence will be monitored 3-day food diaries, weekly remote consultations, and digital tools. Participants will receive vitamin D supplementation (2000 IU/day).
Experimental: Vegan diet, asthmatic individuals	Behavioral: Vegan diet; Participants will follow an individually planned, nutritionally adequate isocaloric vegan diet for 12 weeks. Diet plans will be prepared by a clinical dietitian. Adherence will be monitored 3-day food diaries, weekly remote consultations, and digital tools. Participants will receive vitamin D supplementation (2000 IU/day) and vitamin B12 supplementation according to standard recommendations.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in hsCRP levels	Change in serum high-sensitivity C-reactive protein (hsCRP) concentration as a marker of systemic inflammation.	Baseline and after week 12
Change in IL-4 levels	Change in serum interleukin-4 (IL-4) levels as an indicator of Th2-mediated inflammatory response.	Baseline and after week 12
Change in IL-5 levels	Change in serum interleukin-5 (IL-5) levels as a marker of eosinophilic inflammation.	Baseline and after week 12
Change in IL-13 levels	Change in serum interleukin-13 (IL-13) levels associated with allergic airway inflammation.	Baseline and after week 12
Change in TNF-α levels	Change in tumor necrosis factor alpha (TNF-α) levels as a marker of systemic inflammatory activity.	Baseline and after week 12

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in lymphocyte subpopulations	Changes in lymphocyte subpopulations including CD4+, CD8+, CD4+/CD8+ ratio, and Treg cells	Baseline and after week 12
Change in serum IgE levels	Change in immunoglobulin E concentration associated with allergic inflammation.	Baseline and after week 12
Change in serum IgA levels	Change in immunoglobulin A concentration reflecting mucosal immune function.	Baseline and after week 12
Change in serum IgG levels	Change in total immunoglobulin G concentration.	Baseline and after week 12
Change in IgG subclasses	Changes in IgG subclasses including IgG1, IgG2, IgG3 and IgG4.	Baseline and after week 12
Change in fractional exhaled nitric oxide (FeNO)	Measurement of airway inflammation assessed using fractional exhaled nitric oxide.	Baseline and after week 12
Change in spirometry parameters	Changes in pulmonary function parameters (FEV1, FVC, FEV1/FVC)	Baseline and after week 12
Change in Asthma Control Test (ACT) score	Change in asthma symptom control measured using the Asthma Control Test (ACT). The ACT is a validated 5-item questionnaire with scores ranging from 5 to 25, where higher scores indicate better asthma control.	Baseline and after week 12
Change in lipid profile	Changes in total cholesterol, HDL-cholesterol, LDL-cholesterol, non-HDL cholesterol, and triglycerides	Baseline and after week 12
Change in body weight	Change in body weight measured in kilograms during the intervention.	Baseline and after week 12
Change in body mass index (BMI)	Change in BMI calculated from weight and height (kg/m²).	Baseline and after week 12
Change in waist circumference	Change in waist circumference as a measure of central adiposity	Baseline and after week 12
Change in waist-to-hip ratio (WHR)	Change in waist-to-hip ratio as a measure of body fat distribution.	Baseline and after week 12
Change in body composition	Changes in fat mass and lean mass assessed by bioimpedance analysis	Baseline and after week 12

Collaborators and Investigators

• Sponsor: Medical University of Gdansk

Study record dates

Study Major Dates

• Study Start (Estimated): March 1, 2026
• Primary Completion (Estimated): December 1, 2028
• Study Completion (Estimated): September 30, 2029

Study Registration Dates

• First Submitted: March 7, 2026
• First Submitted That Met QC Criteria: March 14, 2026
• First Posted (Actual): March 18, 2026

Study Record Updates

• Last Update Posted (Actual): March 18, 2026
• Last Update Submitted That Met QC Criteria: March 14, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: asthma; inflammation; asthma control; randomized control trial; inflammatory markers; dietary intervention; immune response; plant-based diet; vegan diet
• Additional Relevant MeSH Terms: Pathologic Processes; Immune System Diseases; Respiratory Tract Diseases; Lung Diseases; Bronchial Diseases; Lung Diseases, Obstructive; Respiratory Hypersensitivity; Hypersensitivity, Immediate; Hypersensitivity; Pathological Conditions, Signs and Symptoms; Asthma; Inflammation; Therapeutics; Diet, Food, and Nutrition; Physiological Phenomena; Nutritional Physiological Phenomena; Diet, Plant-Based; Diet Therapy; Nutrition Therapy; Diet; Diet, Vegetarian; Diet, Vegan
• Other Study ID Numbers: KB/556-86/2026

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No