Edible and Medicinal Mushrooms in Metabolic Syndrome: From Mechanistic Plausibility to Clinical Evidence—A Narrative Review

Background: Edible and medicinal mushrooms contain bioactive compounds potentially relevant to metabolic syndrome (MetS). Methods: This narrative review was based on searches of PubMed and Embase from database inception to 10 April 2026. In vitro, in silico, animal and human studies, and systematic reviews were considered. Evidence was mapped by species, preparation, evidence level and outcome, distinguishing MetS diagnostic components from related outcomes. Results: The evidence was predominantly preclinical and addressed glucose and lipid metabolism, adiposity, inflammation, oxidative stress and gut microbiota. Human evidence was dominated by Ganoderma lucidum. The only randomized trial in participants with diagnosed MetS that assessed its diagnostic components (n = 84) found no effect of G. lucidum, alone or combined with Cordyceps sinensis, on glycemia, blood pressure, lipids, waist circumference or MetS status. Systematic reviews reported no significant effects on fasting blood glucose, blood pressure or lipid profile and a small reduction in body mass index without a corresponding change in waist circumference, although the certainty of evidence was very low. Individual, unreplicated trials reported improvements in specific components. Conclusions: Mechanistic plausibility has not translated into demonstrated clinical efficacy. Insufficient chemical characterization and standardization of preparations preclude species-specific recommendations. Trials of standardized preparations in participants with diagnosed MetS are needed.