Long-term increase in Mediterranean diet adherence combined with decrease in ultra-processed food consumption is...

Mediterranean diet (MD) has been associated with a reduced risk of depressive symptoms, while high intake of ultra-processed foods (UPFs) has been linked to poorer mental health. However, the long-term combined effects of changes in MD adherence and UPF consumption on depressive symptoms remain poorly investigated. The aim of the study was to examine how joint trajectories of MD adherence and UPF consumption over the long term relates to changes in depressive symptoms.

We longitudinally analysed data from 1417 adults (54% women, mean age 54 yr) in the Moli-sani Study (Italy, 2005-2010), with repeated dietary and health assessments over a median 12.7-year. MD adherence was measured by the Mediterranean Diet Score (MDS), and UPF intake classified via the Nova system. Depressive symptoms were assessed using the Patient Health Questionnaire-2 (PHQ-2).

Both increased adherence to the MD and reduced UPF consumption over time were independently associated with marginal reductions in PHQ-2 scores. Compared to the group "reduced MDS/increased UPF", participants with the dietary pattern "increased MDS/reduced UPF" showed a greater decrease in PHQ-2 scores (β = -0.42 points; 95%CI: -0.73 to -0.12). Those who increased adherence to MD but maintained stable UPF also showed reduced depressive symptoms (β = -0.44; -0.74 to -0.13), as well as those with stable adherence to MD who reduced UPF (β = -0.43; -0.67 to -0.18).

Depressive symptoms declined when UPF consumption was reduced (particularly among participants with stable MD adherence) and when MD adherence increased provided that UPF intake did not increase. Changes in MDS or UPF alone were weakly associated, suggesting that combined dietary improvements are needed for meaningful mental health benefits. Promoting healthy diets that limit UPFs may thus maximize prevention of depressive symptoms..