title: Dietary pattern and asthma: a systematic review and meta-analysis.
abstract: BACKGROUND
  The literature on the relationship between diet and asthma has largely focused on individual nutrients, with conflicting results. People consume a combination of foods from various groups that form a dietary pattern. Studying the role of dietary patterns in asthma is an emerging area of research. The purpose of this study was to systematically review dietary patterns and asthma outcomes in adults and children, to review maternal diet and child asthma, and to conduct a meta-analysis on the association between asthma prevalence and dietary patterns in adults.
  
  
  METHODS
  We searched Medline, Scopus, and ISI Web of Knowledge up to January 2014. Two researchers independently reviewed studies meeting the inclusion criteria using the American Dietetic Association quality criteria. A linear mixed model was used to derive the pooled effect size (95% confidence interval) for each of three dietary pattern categories (healthy, unhealthy, and neutral).
  
  
  RESULTS
  Thirty-one studies were identified (16 cross-sectional, one case-control, 13 cohort, and one randomized controlled trial), including 12 in adults, 13 in children, five in pregnant woman-child pairs, and one in both children and pregnant woman-child pairs. Six of the 12 adult studies reported significant associations between dietary patterns and asthma outcomes (eg, ever asthma and forced expiratory volume in one second). Seven of ten studies examining the Mediterranean diet showed protective effects on child asthma and/or wheeze. Four of the six studies in mother-child pairs showed that maternal dietary patterns during pregnancy were not associated with child asthma or wheeze. The meta-analysis including six adult studies, the primary outcome of which was the prevalence of current or ever asthma, showed no association with healthy, unhealthy, or neutral dietary patterns.
  
  
  CONCLUSIONS
  The evidence suggests no association of dietary patterns with asthma prevalence in adults or of maternal diet with child asthma or wheeze. The Mediterranean diet in children may prevent asthma or wheeze, but randomized controlled trials are lacking.
authors.affiliation: Palo Alto Medical Foundation Research Institute, Stanford, CA, USA.
authors.forename: Nan
authors.initials: N
authors.lastname: Lv
authors.affiliation: Palo Alto Medical Foundation Research Institute, Stanford, CA, USA.
authors.forename: Lan
authors.initials: L
authors.lastname: Xiao
authors.affiliation: Palo Alto Medical Foundation Research Institute, Stanford, CA, USA ; Department of Medicine, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Ma
keywords: adults; asthma; children; dietary pattern; meta-analysis; systematic review