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Background: Diet can help preserve lung function in smokers, as well as aid individuals who avoid smoking. This study aimed to evaluate the effectiveness of a nutritional intervention, using the Social Networks 2.0 tool, to increase adherence to the Mediterranean diet (MD) and improve lung function in smokers without prior respiratory disease., Methods: A randomized controlled parallel design was used. The participants were assigned to either the intervention or control group. Data from representative smokers without respiratory disease ( n = 77) aged 18-70 years were analyzed. The participants completed a validated semi-quantitative food-frequency questionnaire, and their adherence to the diet was evaluated by using the questionnaire called the Mediterranean Diet Adherence Score (MEDAS, with 14 items), which considers ≥9 points to indicate high adherence. The lung function was assessed by spirometry. Associations among variables were determined by logistic regression., Results: A comparison of the variables at the end of the study between the control and intervention groups showed that the intervention significantly increased adherence to the MD based on the MEDAS questionnaire (0.69 (2.1) vs. 2.05 (2.03); p = 0.009). Specifically, the consumption of fruits was increased after two years in both groups; however, a more significant increase was detected in the intervention group (121 (178) vs. 12.7 (167) in the control group; p -value = 0.008). In the unadjusted analysis, the intervention only showed a statistical significant increase in the score of adherence to the MD (β: 1.36; 95% CI 0.35; 2.3; p = 0.009), and this increase was maintained after adjusting for age and sex (β: 1.15; 95% CI 0.05; 2.2; p = 0.040) and after adjusting for various sociodemographic, lifestyle and anthropometric variables (β: 1.17; 95% CI 0.02; 2.31; p = 0.046). The pulmonary function parameters improved more in the intervention group; however, no significant differences were observed between the two groups., Conclusions: A nutritional intervention based on a dietetic-nutritional education program resulted in a significant increase in adherence to the MD. However, some evidence suggests that an MD dietary intervention can improve lung function, but in our study, we were not able to demonstrate this. Further research is needed to obtain more robust data and confirm a possible benefit of the program before it can be extended to general practice.

Data on the association between lung function and some dietary patterns have been published. However, it is not yet well known if whether the Mediterranean Diet (MD) pattern can preserve or improve lung function. Our purpose is to evaluate the effect of increased MD adherence on lung function in smokers. A multicenter, parallel, cluster-randomized, controlled clinical trial is proposed. A total of 566 active smokers (>10 packs-year), aged 25-75 years will be included, without previous respiratory disease and who sign an informed consent to participate. Twenty Primary Care Centres in Tarragona (Spain) will be randomly assigned to a control or an intervention group (1:1). All participants will receive advice to quit smoking, and the intervention group, a nutritional intervention (2 years) designed to increase MD adherence by: (1) annual visit to deliver personalized nutritional education, (2) annual telephone contact to reinforce the intervention, and (3) access to an online dietary blog. We will evaluate (annually for 2 years): pulmonary function by forced spirometry and MD adherence by a 14-item questionnaire and medical tests (oxidation, inflammation and consumption biomarkers). In a statistical analysis by intention-to-treat basis, with the individual smoker as unit of analysis, pulmonary function and MD adherence in both groups will be compared; logistic regression models will be applied to analyze their associations. We hope to observe an increased MD adherence that may prevent the deterioration of lung function in smokers without previous respiratory disease. This population may benefit from a dietary intervention, together with the recommendation of smoking cessation.