Manipulating Antioxidant Intake in Asthma: A Randomized Controlled Trial

Am J Clin Nutr. 2012 Sep;96(3):534-43. doi: 10.3945/ajcn.111.032623. Epub 2012 Aug 1.

Abstract

Background: Antioxidant-rich diets are associated with reduced asthma prevalence in epidemiologic studies. We previously showed that short-term manipulation of antioxidant defenses leads to changes in asthma outcomes.

Objective: The objective was to investigate the effects of a high-antioxidant diet compared with those of a low-antioxidant diet, with or without lycopene supplementation, in asthma.

Design: Asthmatic adults (n = 137) were randomly assigned to a high-antioxidant diet (5 servings of vegetables and 2 servings of fruit daily; n = 46) or a low-antioxidant diet (≤2 servings of vegetables and 1 serving of fruit daily; n = 91) for 14 d and then commenced a parallel, randomized, controlled supplementation trial. Subjects who consumed the high-antioxidant diet received placebo. Subjects who consumed the low-antioxidant diet received placebo or tomato extract (45 mg lycopene/d). The intervention continued until week 14 or until an exacerbation occurred.

Results: After 14 d, subjects consuming the low-antioxidant diet had a lower percentage predicted forced expiratory volume in 1 s and percentage predicted forced vital capacity than did those consuming the high-antioxidant diet. Subjects in the low-antioxidant diet group had increased plasma C-reactive protein at week 14. At the end of the trial, time to exacerbation was greater in the high-antioxidant than in the low-antioxidant diet group, and the low-antioxidant diet group was 2.26 (95% CI: 1.04, 4.91; P = 0.039) times as likely to exacerbate. Of the subjects in the low-antioxidant diet group, no difference in airway or systemic inflammation or clinical outcomes was observed between the groups that consumed the tomato extract and those who consumed placebo.

Conclusions: Modifying the dietary intake of carotenoids alters clinical asthma outcomes. Improvements were evident only after increased fruit and vegetable intake, which suggests that whole-food interventions are most effective. This trial was registered at http://www.actr.org.au as ACTRN012606000286549.

Publication types

  • Comparative Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Antioxidants / administration & dosage
  • Antioxidants / adverse effects
  • Antioxidants / therapeutic use*
  • Asthma / blood
  • Asthma / diet therapy*
  • Asthma / immunology
  • Asthma / physiopathology
  • C-Reactive Protein / analysis
  • Carotenoids / adverse effects
  • Carotenoids / analysis
  • Carotenoids / therapeutic use
  • Diet / adverse effects
  • Dietary Supplements / adverse effects
  • Double-Blind Method
  • Female
  • Fruit* / adverse effects
  • Fruit* / chemistry
  • Humans
  • Inflammation Mediators / blood
  • Lycopene
  • Lycopersicon esculentum / adverse effects
  • Lycopersicon esculentum / chemistry
  • Male
  • Middle Aged
  • Oxidative Stress*
  • Patient Dropouts
  • Plant Extracts / adverse effects
  • Plant Extracts / chemistry
  • Plant Extracts / therapeutic use
  • Respiratory System / physiopathology
  • Vegetables* / adverse effects
  • Vegetables* / chemistry

Substances

  • Antioxidants
  • Inflammation Mediators
  • Plant Extracts
  • Carotenoids
  • C-Reactive Protein
  • Lycopene