Nutrition and Metabolic Diseases: A Systematic Review of Functional Foods, Medicinal Plants, Phytochemicals, Bioactive Compounds and Nutrients Effective Against Metabolic Diseases

ABSTRACT

Metabolic diseases, including type 2 diabetes mellitus (T2DM), obesity, metabolic dysfunction‐associated steatotic liver disease (MASLD) and metabolic syndrome, continue to increase worldwide, posing a substantial global public health burden. Growing evidence suggests that functional foods, medicinal plants, phytochemicals, bioactive compounds and specific nutrients may complement conventional therapeutic approaches by modulating metabolic pathways associated with these conditions. This systematic review synthesised evidence published between 2016 and 2026 from PubMed, Scopus, PubMed Central, Google Scholar, Wiley Online Library, Taylor & Francis Online, etc., following the PRISMA 2020 guidelines. Studies were selected using predefined inclusion and exclusion criteria and methodological quality was assessed using established risk‐of‐bias tools appropriate to study design. A total of 89 studies were included in the qualitative synthesis. Berberine demonstrated clinically relevant improvements in insulin sensitivity and glycaemic control in patients with T2DM, while choline supplementation showed promise in reducing hepatic steatosis and oxidative stress in MASLD. Functional foods such as oats and legumes contributed to improved lipid metabolism and glucose regulation through dietary fibre and β‐glucan, whereas phytochemicals including curcumin and eugenol exhibited anti‐inflammatory and antioxidant activities by modulating pathways such as AMP‐activated protein kinase (AMPK) and nuclear factor erythroid 2‐related factor 2 (NRF2). Although many studies reported favourable metabolic outcomes, considerable heterogeneity was observed across intervention types, study populations, dosages, formulations and outcome measures. Furthermore, limited bioavailability, variability in formulation and inconsistent dosing protocols remain major barriers to clinical translation. Overall, current evidence supports the potential of these natural interventions as complementary approaches alongside conventional therapies for metabolic disease management. However, larger, well‐designed randomised controlled trials with standardised interventions are required to establish long‐term efficacy, optimal dosing and clinical applicability.