Chinese Yam/Shān Yào 山藥

A 2025 systematic review pooled 27 studies (two human trials, 25 animal experiments) on Chinese yam rhizome and gut health. The authors noted that clinical trials reported improvements in gut-microbiota balance, glycaemic control and post-surgical recovery, while animal models showed reduced inflammation, stronger antioxidant defences and better mucosal-barrier integrity. More rigorous human trials are still needed.

A 2022 PRISMA-guided review found ten eligible studies, all in rodent models of diabetes. Every study reported that yam or its extracts (containing dioscin, dioscorin, diosgenin or Chinese yam polysaccharides) improved fasting blood glucose and glucose-tolerance responses, with several also noting improvements in body weight and lipid markers. Human evidence remains lacking.

In a small placebo-controlled crossover trial, 28 healthy Japanese adults took a diosgenin-rich yam extract in olive-oil capsules for 12 weeks. Research suggests the extract was associated with significant improvements on a standardised neurocognitive battery (RBANS) compared with placebo, with no notable adverse effects in blood testing. Larger trials would be needed to confirm this.

A 2024 review summarised around 30 isolated yam polysaccharide fractions and their reported activities. In laboratory and animal studies these polysaccharides showed immunomodulatory, hypoglycaemic, lipid-lowering, antioxidant, gut-protective, anti-fatigue and prebiotic effects, with structure-activity relationships depending on molecular weight and chemical modification. The authors framed these as prospects rather than proven clinical benefits.