Quick answer: Gymnema may modestly lower glucose and blunt sweet taste; cinnamon studies are mixed with small effects; chromium shows small, inconsistent benefits mainly in type 2 diabetes. All three can add to diabetes medicines.
Gymnema
Small trials at 400 to 500 mg of extract found modest glucose drops.
Ceylon cinnamon
Lower in coumarin than cassia, which matters for the liver. NCCIH on cinnamon.
Chromium
Effects are small and inconsistent. NIH ODS.
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General information, not medical advice. GlycoZen is a dietary supplement and is not intended to diagnose, treat, cure or prevent any disease.