Banaba (corosolic acid, Lagerstroemia speciosa)
Filipino tropical leaf with preliminary RCT signal for postprandial glucose at 32–48 mg corosolic acid daily.
Why
Banaba (Lagerstroemia speciosa) leaf has been used in Filipino folk medicine for diabetes. The active corosolic acid was identified in the 1990s; small Japanese RCTs (Ikeda 2002, Fukushima 2006) report reductions in fasting and postprandial glucose in mild type 2 diabetes at 32–48 mg corosolic acid daily. Evidence base is small and primarily Asian; Western RCTs are sparse.
How it works
Corosolic acid stimulates GLUT4 translocation to the skeletal muscle plasma membrane (insulin-mimetic effect) and inhibits intestinal α-glucosidase. Independent mechanisms produce additive glycaemic effect.
Expected onset · Postprandial effect acute; HbA1c effects over 8–12 weeks
How to take
Dosage
Standardised banaba extract delivering 32–48 mg corosolic acid daily, often as 1% standardised at ~3–5 g/day, or 18% standardised at 0.5 g/day.
Timing
Before main meals
On the label
Standardised to corosolic acid content (1–18% depending on extract). Stated milligrams of corosolic acid per dose is the more useful metric than extract weight.
Ideal for
Adults with prediabetes or mild type 2 diabetes exploring botanical adjuncts.
Safety
Evidence
Fukushima 2006 Diabetes Res Clin Pract RCT (n=31): corosolic acid 10 mg significantly lowered postprandial glucose over 60–120 min vs placebo. Klein 2007 review collated preclinical and clinical evidence for the insulin-mimetic mechanism. Preliminary evidence, no Cochrane review, EMA HMPC monograph or EFSA-authorised health claim covers this indication; cited RCTs are small or in non-tier-1 journals. Useful as honest reference rather than evidence-grade recommendation.
Preliminary evidence, no Cochrane review, EMA HMPC monograph or EFSA-authorised health claim covers this indication; cited RCTs are small or in non-tier-1 journals. Useful as honest reference rather than evidence-grade recommendation.
- Fukushima et al., Diabetes Res Clin Pract 2006, effect of corosolic acid on postchallenge plasma glucose levels (RCT)
- Ikeda et al., Yakugaku Zasshi 2002, effect of banaba leaf extract on type 2 diabetes (RCT)
- Klein et al., J Med Food 2007, antihyperglycemic activity of Banaba (Lagerstroemia speciosa) leaves and corosolic acid (review)
Where to get it
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