Adjunctive nutritional interventions in schizophrenia: A systematic review of randomised clinical trials

Background & aims Schizophrenia is a serious mental disorder involving cognitive, metabolic and functional impairments, often exacerbated by the side effects of pharmacological treatment. In this context, nutritional interventions have been investigated as adjunctive strategies aimed at improving clinical and metabolic outcomes. This study aimed to evaluate the effectiveness of nutritional interventions in schizophrenia, considering different dietary approaches and nutritional supplements. Methods A systematic review was conducted according to Cochrane recommendations, including randomised clinical trials investigating nutritional supplementation or dietary interventions in patients with schizophrenia and evaluating clinical, metabolic and cognitive outcomes. Data selection and extraction were performed independently by two reviewers, and methodological quality was assessed using validated instruments. Results Nine randomised clinical trials were included. Probiotic-based interventions, particularly when combined with vitamin D or selenium, were associated with improvements in metabolic parameters and selected inflammatory markers. n-3 fatty acid supplementation demonstrated effects on triglyceride concentrations and neurotrophic markers. Plant-derived bioactive compounds were associated with improvements in negative symptoms and stress-related measures. However, findings varied across studies, reflecting heterogeneity in intervention protocols, dosage regimens and outcome assessment. Conclusion Findings suggest that nutritional interventions may act as adjunctive strategies in schizophrenia, with observed effects on metabolic, inflammatory and selected neuropsychiatric parameters. However, methodological heterogeneity, limited sample sizes and short follow-up durations warrant cautious interpretation. Further well-designed, adequately powered randomised clinical trials are needed to clarify clinical applicability and long-term implications. © 2026 European Society for Clinical Nutrition and Metabolism.