Relationship between dietary patterns and asthma: A systematic review and meta-analysis

RATIONALE: The findings from previous studies investigating the association between asthma and dietary patterns are inconsistent. OBJECTIVES: The objective of this review is to summarize the current evidence on the association between dietary patterns and asthma risk. METHODS: We searched seven databases (MEDLINE, Embase, Web of Science, CINAHL, LILACS, AMED and the Cochrane database) for articles published between January 1, 1980 and November 30, 2019 that reported on dietary patterns and asthma. Pairs of reviewers independently reviewed each study at all stages: screening, selection, data extraction and quality assessment. MEASUREMENTS: Summary estimates of dietary patterns and asthma are reported from random effects meta-analysis. MAIN RESULTS: Out of 12,730 articles identified, 36 studies met the inclusion criteria for this review. Directionally, consumption of the Mediterranean Diet (RR 0.88; CI 0.74–1.05) was associated with a lower risk for asthma, whereas consumption of the Western Diet (1.10; 0.95–1.28) and Prudent Diet (1.09; 0.98–1.20) has higher risk. However, these effects are small and statistically not significant. There were insufficient studies to meta-analyze spirometric, mortality or quality of life indices. CONCLUSIONS: Overall, adherence to the Mediterranean, Western, or Prudent Diets was not associated with a statistically significant difference in the risk of developing asthma. However, current evidence in this area comes primarily from observational studies of varying qualities, and larger well-designed longitudinal studies or randomized controlled trials are needed.