Banaba Leaf
Lagerstroemia speciosa
A Philippine folk remedy for diabetes whose leaves contain corosolic acid, an insulin-sensitizing triterpene with small-trial evidence for lowering blood sugar.
At a Glance
- Best known for
- Lowers fasting and post-meal blood glucose in small trials, Improves insulin sensitivity via corosolic acid, Antioxidant ellagitannins
- Evidence
- Preliminary
- Typical dose
- 32–48 mg extract (1% corosolic acid) daily
- Type
- Herb
What is Banaba Leaf?
Banaba (Lagerstroemia speciosa), also known as pride of India or giant crape myrtle, is a flowering tree native to the Philippines, India, and Southeast Asia, prized for its showy purple blossoms. In the Philippines the leaves have been brewed as a tea for diabetes and kidney complaints for centuries, and banaba is one of the traditional remedies recognized by the Philippine Department of Health. Research since the 1990s has identified corosolic acid as the main glucose-lowering component, and standardized extracts (such as Glucosol and GlucoTrim) have been studied in small trials in Japan and the United States.
Known Health Benefits
How It Works
Corosolic acid improves insulin sensitivity by enhancing insulin receptor signaling and increasing translocation of GLUT4 glucose transporters to the cell membrane in muscle and fat cells, promoting glucose uptake. It inhibits protein tyrosine phosphatase 1B (PTP1B), an enzyme that normally switches off insulin signaling, and inhibits intestinal alpha-glucosidase and alpha-amylase, slowing carbohydrate digestion. It also reduces gluconeogenesis in the liver. Banaba's ellagitannins (lagerstroemin, flosin B, reginin A) have independent insulin-mimetic activity, stimulating glucose transport in adipocytes, and provide antioxidant effects. Animal studies also show reduced triglycerides and body weight gain, possibly via PPAR modulation.
What Research Says
Human evidence consists of a few small trials. A 2003 study of 10 people with type 2 diabetes found a standardized banaba extract (Glucosol, 1% corosolic acid) at 48 mg daily for 2 weeks reduced blood glucose by about 30% compared with baseline, with the soft-gel form outperforming hard capsules. A 2006 Japanese study of 31 adults found a single 10 mg dose of corosolic acid lowered the post-meal glucose rise during an oral glucose tolerance test. A 2012 review by Stohs and colleagues summarized animal and human data and concluded banaba and corosolic acid had consistent glucose-lowering effects and a good safety profile, but emphasized that trials were tiny and short. Subsequent small studies, including combinations with cinnamon or chromium, have reported modest reductions in fasting glucose. No adequately powered, long-term, placebo-controlled trial has been conducted, so the evidence remains preliminary.
Active Compounds
Corosolic acid (pentacyclic triterpene), ellagitannins (lagerstroemin, flosin B, reginin A), ellagic acid, gallotannins, flavonoids
Forms & Bioavailability
Corosolic acid is a lipophilic triterpene with limited water solubility; the 2003 trial found a soft-gel oil-based formulation produced greater glucose reduction than a dry capsule, suggesting better absorption with lipids. Plasma levels peak around 1–2 hours after dosing and the effect on a glucose load appears within that window. Leaf tea delivers very little corosolic acid but does provide ellagitannins. Taking extracts with a meal containing fat is sensible.
Dosage Guidance
| Use Case | Dosage |
|---|---|
| Blood sugar support (standardized extract) | 32–48 mg extract (1% corosolic acid) daily |
| Corosolic acid (concentrated) | 10 mg before carbohydrate-rich meals |
| Daily metabolic support | 10–60 mg corosolic acid daily |
| Leaf tea | 1–2 g dried leaf steeped 10 min, 1–2 cups daily |
Always consult a healthcare provider for personalized dosing.
Natural Food Sources
- Banaba leaf tea (traditional Philippine beverage)
- Not otherwise found in food
- Corosolic acid also occurs in small amounts in apple peel and loquat leaves
Potential Side Effects
Generally well tolerated in trials; possible hypoglycemia with diabetes drugs; mild stomach upset; theoretical kidney effects with long-term high-dose tannin intake
Who Should Avoid It
- Insulin or sulfonylurea therapy without glucose monitoring (hypoglycemia)
- Pregnancy and breastfeeding (no safety data)
- Kidney impairment (tannin load; a case of acute kidney injury with concurrent diclofenac)
- Scheduled surgery (stop 2 weeks before)
- Hypoglycemia-prone individuals
Pregnancy & Lactation
Avoid. No safety data exist for banaba or corosolic acid during pregnancy or lactation, and its glucose-lowering effects could interfere with management of gestational diabetes.
Known Drug Interactions
Additive hypoglycemia with insulin and oral diabetes medications; may interact with drugs metabolized by CYP enzymes (corosolic acid inhibits some in vitro); one report of nephrotoxicity with concurrent diclofenac
Evidence Classification
Based on in vitro studies, animal models, pilot trials, or traditional use documentation. Clinical evidence is limited.
Frequently Asked Questions
How does banaba compare with other herbal glucose supports?
Banaba has a clear active compound (corosolic acid) with a well-described insulin-sensitizing mechanism, but far fewer and smaller human trials than berberine, which has the strongest evidence among botanicals. It is often combined with gymnema, bitter melon, cinnamon, or chromium in formulas. Think of it as a plausible but lightly studied option, not a first-line one.
Is banaba tea as effective as extract?
Probably not for blood sugar. Corosolic acid is poorly water-soluble, so tea contains little of it; the tea's benefits come mainly from ellagitannins and antioxidants. Standardized extracts, especially oil-based softgels, deliver the doses used in trials.
Can banaba help with weight loss?
Animal studies show reduced weight gain and fat accumulation, and improving insulin sensitivity may indirectly help with weight management, but there are no convincing human trials for weight loss. Any product claiming substantial fat loss from banaba is overreaching.
Is it safe for the kidneys?
Traditionally banaba was used for kidney complaints, and trials have not shown kidney harm at normal doses. However, a published case of acute kidney injury in a person taking banaba with diclofenac, plus the high tannin content, means people with kidney disease or on NSAIDs should use it cautiously and discuss it with their doctor.
References
- A review of the efficacy and safety of banaba (Lagerstroemia speciosa L.) and corosolic acid. Stohs SJ, Miller H, Kaats GR. Phytother Res (2012)View study
- Antidiabetic activity of a standardized extract (Glucosol) from Lagerstroemia speciosa leaves in Type II diabetics. A dose-dependence study. Judy WV, Hari SP, Stogsdill WW, et al.. J Ethnopharmacol (2003)View study
- Corosolic acid induces GLUT4 translocation in genetically type 2 diabetic mice. Miura T, Itoh Y, Kaneko T, et al.. Biol Pharm Bull (2004)
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