The impact of Mediterranean diet adherence on allergic diseases: a systematic review and meta-analysis

Allergies are a growing public health concern worldwide. This meta-analysis investigated the association between adherence to the Mediterranean diet (MD) and the occurrence/severity of respiratory allergic conditions. Electronic databases (PubMed, Scopus, Science Direct, and EBSCO) were searched for studies published up to April 2024. Eligible studies reported OR with 95% CI for asthma, wheezing (respiratory symptom associated with allergic airway disease), rhinitis, or eczema. Food allergy was evaluated only qualitatively due to insufficient data. The risk of bias was assessed using the National Heart, Lung, and Blood Institute tool, and random-effects models were applied to account for heterogeneity. A total of twenty-three studies involving 111,583 participants met the inclusion criteria. Individual studies could contribute to more than one condition-specific analysis if they reported outcomes for multiple allergic conditions. Pooled analyses demonstrated a significant protective effect of MD against asthma (n = 11, log OR: -0.18; 95% CI: -0.34, -0.02), wheezing (n = 6, log OR: -0.29; 95% CI: -0.56, -0.03), and rhinitis (log OR: -0.54; 95% CI: -1.00, -0.08), with stronger effects in Mediterranean populations. No significant association was observed with eczema (pooled log OR: 0.09; 95% CI: -0.02, 0.20). Heterogeneity was moderate across analyses. Publication bias was evaluated using forest plots and Egger's test. These findings suggest that MD adherence was associated with lower odds of asthma, wheezing, and rhinitis, but does not influence eczema risk. Further longitudinal studies with standardised methodologies are needed to confirm causality. Promoting MD adherence may offer a valuable population-level strategy for allergy prevention. Systematic review registration: PROSPERO-CRD42023408724.