Determinants of adherence to the Mediterranean diet among adults in Mediterranean countries: a systematic literature review

OBJECTIVE: This study aims to provide an overview of evidence on factors affecting Mediterranean diet (MD) adherence across socio-ecological levels (individual, interpersonal and environmental) in Mediterranean countries, which can be target points for future interventions to promote MD adherence.

DESIGN: A systematic review was conducted following the PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analysis) guidelines and registered in the Prospero database (CRD42020189337). Literature was searched in PubMed, Web of Science and PsycINFO.

SETTING: The MD is one of the healthiest dietary patterns, reducing risk of chronic disease while promoting better health outcomes. However, adherence to the MD remains challenging, even in Mediterranean countries.

PARTICIPANTS: Healthy adults aged 18 years and older, living in a Mediterranean country.

RESULTS: A total of thirty-seven cross-sectional studies were included, with 190 to 13 262 participants. Most studies (30/37) were conducted in European Mediterranean countries, primarily Italy ( n 14), Spain ( n 9) and Greece ( n 6). All studies involved community-based samples; two studies included only women. Individual-level determinants were the most frequently examined. Higher socio-economic status, regular breakfast consumption, being unemployed, a job seeker or retired were linked to better MD adherence. Socio-cognitive and interpersonal factors were underexplored. At the environmental level, COVID-19 confinement boosted adherence, whereas the effects of economic crises were inconsistent. Effect sizes were mostly very small to small, and findings are based on low-quality studies.

CONCLUSIONS: This systematic review highlighted several socio-economic and environmental factors potentially influencing MD adherence. However, more robust research is needed to better understand socio-cognitive and ecological factors.