Exploring Plant-Based Diets and Mental Health Outcomes: A Systematic Review

Plant-based diets are increasingly recognized for their potential benefits on gut microbiota and mental health. This systematic review examines the impact of vegan or strictly plant-based diets (encompassing both whole-food and processed plant-based dietary patterns) on anxiety, depression, and eating disorders. PubMed, Scopus, CINAHL, and PsycInfo were searched for studies published after 2015. Inclusion criteria focused on peer-reviewed research measuring mental health outcomes in participants adhering to plant-based diets. Non-peer-reviewed studies and those lacking essential clinical data were excluded. A total of 560 articles were identified through database searches, and after removing duplicates, 513 articles were screened, with 13 meeting the inclusion criteria. These studies involved 8,110 participants (2,336 plant-based; 5,774 control). Study designs included observational studies, one prospective study, and one randomized controlled trial (RCT). Participants following plant-based diets showed mental health benefits, including reduced anxiety, depression, and healthier eating behaviors. Diets high in fiber and antioxidants were linked to lower stress, while processed plant-based diets were associated with worsened mood symptoms. Risks of orthorexia nervosa were noted among individuals adopting vegan diets for health reasons, whereas ethical motivations appeared to be protective. Plant-based diets appear to improve anxiety, depression, and eating behaviors, but potential links to disordered eating warrant further research. Variations in study design and inconsistent mental health reporting highlight the need for more randomized controlled trials related to this topic.