Across 3 studies, all 3 reported beneficial effects of konjac (glucomannan) supplementation on reducing fasting blood glucose levels, with effect sizes ranging from small to large. The median study duration was 90 days, suggesting effects typically observed at 12+ weeks. Evidence comes primarily from clinical populations with type 2 diabetes or prediabetes, though doses varied and were not consistently reported.
Caveats: Evidence base is small (only 3 studies) — conclusions should be considered preliminary. Available evidence is overwhelmingly positive — clinical literature in this area is subject to publication bias (null-result studies are less likely to be published or indexed).
one case reported increased anal flatulence
from: [The Effect of Konjac Glucomannan on Blood Glucose and Insulin Levels in Obese Patients Witwo participants in the KGM group experienced severe abdominal discomfort, which resolved after discontinuing the biscuits
from: [The Effect of Konjac Glucomannan on Blood Glucose and Insulin Levels in Obese Patients Witwo cases reported transient diarrhea
from: [The Effect of Konjac Glucomannan on Blood Glucose and Insulin Levels in Obese Patients Wireduced the fasting blood glucose (FBG) (MD -1.08 [95% CI: -1.65, -0.50], p = 0.0002)
The KGM group also had higher effective rates in reducing fasting blood glucose, fasting insulin, insulin resistance, insulin sensitivity, body mass, and waist circumference compared to the control group (P < 0.05).
glucomannan supplementation significantly reduced FBG (WMD): -0.60 mmol/L, 95% CI: -1.16, -0.05; P=0.03