About Banaba (Lagerstroemia speciosa)
Banaba's glucose-lowering activity is attributed mainly to corosolic acid (a pentacyclic triterpene) and ellagitannins, which appear to enhance cellular glucose uptake. A '500 mg banaba at 1% corosolic acid' delivers only ~5 mg corosolic acid, so the standardized active content — not the extract weight — drives the effect. Marketing claims of 'natural insulin' or meaningful weight loss are not supported by clinical data: the human evidence is limited to small (n=10-31), short (≤2-week or acute) blood-glucose trials, mostly in diabetic or pre-diabetic subjects, with no meta-analyses and no large or long-term RCTs. The strongest-looking supportive review (Miura 2012) was retracted. Treat as a low-evidence glycemic adjunct, not a validated intervention.
What Banaba (Lagerstroemia speciosa) supports
- May modestly lower fasting and post-meal blood glucose in type 2 diabetics and people with impaired fasting glucose (small short-term RCTs)
- Corosolic acid may improve glucose response after a carbohydrate load
How much Banaba (Lagerstroemia speciosa) to take
The RDA prevents deficiency. The effective range is what clinical trials used to actually move the outcome.
Effective
32–500
mg
Effective trial doses used concentrated standardized extract: Judy 2003 (Glucosol, ~1% corosolic acid) cut fasting glucose at 48 mg/day over 10 days; a 1-year open-label safety study used 100 mg/day. Commercial products commonly supply 200-500 mg extract standardized to 1-2% corosolic acid (~2-10 mg corosolic acid). The upper end reflects real-world dosing, not a separately validated efficacy ceiling — scoring tracks extract mass, which can overstate products with low corosolic-acid standardization.
Clinical evidence
Limited clinical evidence. Only small, short (≤2-week) RCTs in type 2 diabetic / impaired-fasting-glucose adults show modest glucose reductions; no meta-analyses, no large/long-term trials, effects in non-dysglycemic people unestablished, and a key supportive review (Miura 2012) was retracted
Reference