Ganoderma lucidum as a Functional Bioactive Candidate for Glycemic Regulation: Mechanisms, Preclinical Evidence, and...

Type 2 diabetes mellitus (T2DM) is a major global health challenge that has intensified interest in multi-target nutraceuticals with potential adjunctive benefits. Ganoderma lucidum (Lingzhi/Reishi) is a medicinal mushroom traditionally used in East Asia and is increasingly investigated for its role in glycemic regulation and metabolic disturbances. This review critically synthesizes current evidence on its hypoglycemic effects, focusing on bioactive compounds, molecular mechanisms, and translational limitations. Unlike broader reviews on Ganoderma bioactivity and health-related benefits, this review specifically evaluates the alignment between taxonomic authentication, chemical standardization, preclinical mechanisms, and human clinical evidence in the context of glycemic regulation. This narrative review was based on a targeted literature search conducted in PubMed/MEDLINE, Web of Science, and Scopus for studies published up to October 2025, supplemented by Google Scholar. The included studies comprised in vitro experiments, in vivo animal models, and human clinical trials evaluating glycemic and metabolic outcomes of Ganoderma preparations. In vitro and animal studies indicate that polysaccharides, including β-(1→3)/(1→6)-glucans and proteoglycans such as FYGL, may improve insulin sensitivity via AMPK (AMP-activated protein kinase) and PI3K/Akt pathways, promote GLUT4 (glucose transporter type 4) translocation, suppress hepatic gluconeogenesis, protect pancreatic β-cells, and modulate gut microbiota. In enzyme assays and preclinical models, lanostane-type triterpenoids act primarily by inhibiting α-glucosidase and α-amylase, thereby potentially reducing postprandial glucose excursions. Despite consistent preclinical evidence, clinical findings remain heterogeneous, with the largest randomized controlled trial reporting no significant glycemic benefit. Overall, Ganoderma lucidum shows strong mechanistic plausibility but insufficient clinical evidence for antidiabetic efficacy. Future research should prioritize species authentication, chemical standardization, and adequately powered clinical trials.