TitleIs Mediterranean diet associated with severe asthma control? A multi-center cross-sectional study in Greece.To the Editor,Severe asthma is a heterogenous disease where different phenotypes and endotyping mechanisms are implicated1. Asthma control is an achievable target where some life-changing aspects like smoking cessation, diet and physical activity may also be involved2. The incidence of and mortality from various diseases have been linked to the Mediterranean diet (MD)3. In a previous small study among well-defined asthmatic patients with different severities, we found a trend between adherence to MD and asthma control in severe asthmatics. This trend lacked significance possibly due to the limited number of severe asthma subjects4. Based on the above finding we hypothesized that in a larger cohort of severe asthmatics, adherence to MD could influence asthma control. Therefore, we conducted a cross-sectional study to address the above association using a larger cohort of severe asthmatics, all Mediterranean inhabitants.This study was an observational, multicenter, cross-sectional study. Study methodology and parameters are provided on an online supplement. Adherence to MD during the previous year was assessed through an interviewer-administered Mediterranean Diet Adherence Screener (MEDAS), a 14-item validated questionnaire which aims to capture the consumption of the MD components5,6.Further information for MEDAS is provided on the online supplement. Statistical analysis is also described in the online supplement.The study sample consists of 315 adults with severe asthma (70% females) and mean age 56.6 years (SD=14.3 years) (Table 1). According to the Asthma Control Test (ACT), 68% of the participants had well-controlled asthma (ACT ≥ 20) and 87% did not receive cortisone treatment. Nearly half of the participants (52%) had atopy, 14% were diagnosed with diabetes mellitus and only 25% of them reported high adherence to the Mediterranean diet (MEDAS Score ≥ 10). In this sample of severe asthmatics in Greece, where the Mediterranean dietary pattern is generally prevalent particularly among older adults, higher adherence to MD was associated, albeit not statistically significantly, with well-controlled asthma (Odds Ratio (OR): 1.19, 95% CIs: 0.61, 2.34), after adjusting for a number of characteristics and clinical conditions that could confound the association. (Table 2). Obesity and type 2 diabetes were statistically significantly associated with poorer asthma control while use of biologics was statistically significantly associated with better asthma control (OR: 4.61, 95%CIs: 2.55, 8.32).From an earlier study of our group, there was some indication that MD might be associated with disease control among severe asthmatics4. The present study was carried out to address this hypothesis in a larger sample, yet through a cross-sectional design. Our results do not provide evidence for a beneficial effect of MD, over and beyond treatment and controlling for diet-related co-morbidities. The fact that the study sample is relatively young and adherence is rather low may not provide us with enough variance to detect such an association. This study does not allow us to draw firm conclusions on the association between MD and asthma control in severe asthmatics. However, three meaningful messages can be retrieved. The lack of association between MD and asthma control may decrease the likelihood of diet interventions conferring protection against severe asthma, second and most important biologics remained the cornerstone of treatment interventions for achieving asthma control and finally co-morbidities such as diabetes may influence asthma control in various ways (avoidance of systemic corticosteroids, lower dose of ICS and symptoms mimicking asthma).