Adherence to a Mediterranean diet (MedDiet) appears to reduce the incidence of adult-onset asthma, suggests a recent study, noting that causality cannot be inferred due to its observational design.
“Further studies, ideally with different designs, are warranted to confirm these findings,” said the investigators, adding that “it is crucial not to focus solely on the relationship between diet and asthma.”
A total of 17,127 adults were included in the analysis, with dietary habits and asthma diagnosis obtained from the Seguimiento Universidad de Navarra (SUN) cohort study. They completed a food frequency questionnaire, assessed at baseline and at 10-year follow-up.
Adult-onset asthma was defined as self-reported diagnosis in the last 2 years, recorded in any of the follow-up questionnaires completed every 2 years in participants free of airway disease at baseline.
The investigators measured the Mediterranean Diet Score (MDS) as an indicator of adherence to the MedDiet and came up with four categories of adherence based on the MDS (0‒9 range score). They used multivariable repeated-measurement Cox models, with adjustments for potential confounders.
Over a mean follow-up of 12.8 years, 302 adults (1.76 percent) had been diagnosed with asthma. Multivariate analysis revealed a negative relationship between the risk of newly diagnosed asthma and adherence to the MedDiet. [Respirology 2026;31:352-360]
Participants with the highest adherence to the MedDiet (MDS ≥7 points) were less likely to develop asthma than those with the lowest adherence (MDS ≤2 points; hazard ratio, 0.58, 95 percent confidence interval [CI], 0.36‒0.95; ptrend=0.02).
Fruits and vegetables
“[O]ur findings are consistent with a recent meta-analysis that reported a trend to an inverse association between adherence to the MedDiet or a healthy diet rich in fruits and vegetables and the occurrence of childhood asthma and those of previous meta-analyses,” the investigators said. [Intl J Food Sci Nutr 2024;75:4-30; Ped Allergy Immunol 2013;24:330-338; J Asthma Allergy 2014;7:105-121]
The current findings also supported those of a cross-sectional study using Mendelian randomization, which found a negative association between asthma and intakes of fresh fruit (odds ratio [OR], 0.49, 95 percent CI, 0.32‒0.75; p<0.01) and dried fruit (OR, 0.48, 95 percent CI, 0.33‒0.72; p<0.01). [Front Immunol 2023;14:1126457]
These findings were also consistent with previous observations of Uddenfieldt and colleagues, who reported the association of fish and fruit consumption index with a lower incidence of asthma (HR, 0.78, 95 percent CI, 0.66–0.92). [Respir Med 2010;104:972-980]
“Greater consumption of fish oil, rich in n-3 polyunsaturated fatty acids, exemplified by linolenic acid, plays a protective role through its catabolism products, eicosapentaenoic and docosahexaenoic acids,” the investigators said.
“These products downregulate COX-2 gene expression and participate in competitive inhibition of the catabolism of n-6 polyunsaturated fatty acids, whose products (prostanoids and leukotrienes) have been associated with proinflammatory properties, Th2 promotion, and bronchoconstriction,” they added. [Biochem Soc Trans 2005;33:423-427; J Allergy Clin Immunol 2015;135:1311-1358]
Future studies must include other lifestyle factors, such as socioeconomic status, stress levels, degree of urbanization, and allergies, in the analysis “to better understand and define broader life patterns that may influence asthma incidence and phenotypes,” according to the investigators.