A Randomized Controlled Trial of the Effect of Broccoli Sprouts on Antioxidant Gene Expression and Airway Inflammation in Asthmatics

Abstract

Background: Broccoli sprouts (BS) are the richest source of sulforaphane (SFN), which is a potent inducer of phase II enzymes, which play a critical role in preventing oxidative stress (OS) and inflammation.

Objectives: The objective of this study was to determine if ingestion of whole BS improves airway inflammatory and physiologic outcomes, and OS in adults with asthma and allergic sensitization to an indoor allergen.

Methods: The study is a double-blind, placebo-controlled, randomized trial to compare the effects of BS with placebo (alfalfa sprouts [AS]) on airway inflammation and markers of OS. Forty adults (aged 18-50 years) were randomized to eat either (a) 100 g of BS daily or (b) 100 g of AS daily for 3 days. Fractional exhaled nitric oxide (FENO), forced expiratory volume 1, nasal epithelial and PBMC gene expression, inflammatory and OS biomarkers, and symptoms were assessed both before and after ingestion of the sprouts. The primary outcome variable was the change in FENO. Secondary outcome measures included rhinitis and asthma symptoms, lung function, and OS and inflammatory biomarkers.

Results: BS ingestion for 3 consecutive days did not reduce FENO, despite resulting in a marked increase in serum SFN concentrations (21 vs 22 parts per billion, P = .76). Furthermore, BS consumption did not induce cytoprotective antioxidant genes in either PBMCs or nasal epithelial cells, reduce OS and inflammatory markers, or improve lung function.

Conclusions: Ingestion of whole BS for 3 days does not appear to improve eosinophilic pulmonary inflammation, inflammatory and OS biomarkers, or clinical features of asthma among atopic adults with asthma despite resulting in a marked increase in serum SFN levels.

Trial registration: ClinicalTrials.gov NCT01183923.

Keywords: Antioxidants; Asthma; Broccoli sprouts; FENO; Oxidative stress.

Copyright © 2016 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1

Consort diagram.

Figure 2

Boxplots of serum SFN conjugates (nM) pre and post intervention by treatment group alfalfa sprouts, broccoli sprouts.

Figure 3

Effect of BS ingestion on fractional exhaled nitric oxide. Boxplots of FENO pre and post intervention by alfalfa sprouts and broccoli sprouts.

Figure 4

BS consumption failed to upregulate anti-oxidant gene expression in nasal epithelial cells and peripheral blood mononuclear cells. Boxplots showing relative change in the phase 2 enzyme gene expression from baseline to post-intervention in nasal epithelial cells (A) and peripheral blood mononuclear cells (B).

Figure 4

BS consumption failed to upregulate anti-oxidant gene expression in nasal epithelial cells and peripheral blood mononuclear cells. Boxplots showing relative change in the phase 2 enzyme gene expression from baseline to post-intervention in nasal epithelial cells (A) and peripheral blood mononuclear cells (B).