Socio-Demographic Disparities in Diet and Their Association with Physical and Mental Well-Being: Million-Participant Cross-Sectional Study in Poland.

Background: Dietary habits are key determinants of physical and mental health, yet large-scale, contemporary data on these behaviors and their health correlates are crucial for effective public health policy. This study leverages a uniquely large dataset to quantify the eating behaviors of Polish adults and examines how these behaviors relate to socio-demographic characteristics, health status, and subjective well-being.

Methods: We analyzed data from 1,196,102 adult respondents who participated in the National Poles' Health Test, a recurring online survey, between 2019 and 2024. The study used self-reported data on dietary habits, socio-demographic variables, chronic conditions, and self-assessed physical and mental health. Descriptive statistics and comparative analyses, such as the chi-square test, Student's t-test, or ANOVA, were used.

Results: Our findings reveal stark socio-demographic disparities in nutrition. Younger respondents and lower educational attainment were strongly correlated with more frequent consumption of fast food and sugar-sweetened beverages. Crucially, these unhealthy eating patterns were significantly associated with poorer self-rated physical and, notably, mental health (among people who consumed fast food every day, as many as 16.6% rated their mental health as bad, and 6.7% as very bad). In contrast, higher vegetable and fruit consumption correlated with markedly better health outcomes and greater subjective well-being.

Conclusions: This large-scale study provides evidence of the profound link between diet and both physical and mental well-being in Poland. The results underscore the urgent need for targeted public health strategies aimed at improving dietary behaviors, particularly among younger and less-educated populations. The strong associations between diet, health status, and well-being highlight the importance of integrating nutritional education into both general healthcare and mental health services.