Dietary Patterns and Supplementation in Depression and Anxiety: A Comprehensive Literature Review

Introduction and purpose: Depression and anxiety frequently co-occur and cause substantial functional burden. Nutrition - especially diet quality and supplementation - has been studied as a modifiable factor. This comprehensive literature review summarised evidence on dietary patterns and selected supplements in relation to depressive and anxiety symptoms. Material and methods: A narrative synthesis was performed using 32 articles (systematic reviews/meta-analyses, randomised trials, observational and mechanistic papers). The scope covered diet quality and dietary patterns, whole-of-diet interventions, gut–brain axis concepts, and supplementation with omega-3 fatty acids, B vitamins, magnesium, vitamin D, zinc, and probiotics. Results: Prospective evidence generally linked higher diet quality with lower depression risk. Whole-diet intervention trials showed mixed results, with several studies reporting improvements in depressive outcomes; anxiety outcomes were less consistent. Mechanistic literature supports plausibility through inflammation/oxidative pathways, serotonergic neurotransmission, and diet–microbiota interactions. Among supplements, evidence is most developed for omega-3 fatty acids (dose-response signals for anxiety) and magnesium (benefits in trials and meta-analysis), while findings for vitamin D, B vitamins, zinc and probiotics vary across studies. Conclusions: Diet quality improvement and selected supplements may offer adjunctive benefits for some individuals, but effects are heterogeneous and should not be overgeneralised. Nutritional strategies should be integrated with evidence-based mental health care, with timely clinical assessment and standard treatments used when indicated.