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Limited evidenceHeart & metabolic

Banaba Leaf

Banaba leaf standardized to corosolic acid produces short-term reductions in blood glucose in small human studies, but the trials are tiny, mostly industry-run and decades old, with no HbA1c-level evidence. It is a plausible minor postprandial glucose aid, not a diabetes treatment.

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What the science says

  • Lowers blood glucose Limited evidence

    Reviews summarise human work in which 10-32 mg/day of corosolic acid, or 32-48 mg/day of a 1% corosolic acid extract for 2-4 weeks, produced roughly 5-30% reductions in fasting or postprandial glucose. The largest of these enrolled around 10-30 people each, several were open-label, and none used HbA1c as a properly powered primary endpoint, so the true effect size is unclear.

  • Reduces post-meal glucose spikes acutely Limited evidence

    Purified corosolic acid at 10 mg given before an oral glucose tolerance test lowered glucose within 60-90 minutes in small crossover studies, consistent with enhanced GLUT4 translocation and alpha-glucosidase inhibition seen in vitro. This acute effect is the best-supported claim but rests on very small samples.

  • Causes weight loss Limited evidence

    Anti-obesity effects appear in rodent models and are extrapolated into marketing, but no controlled human trial shows meaningful fat loss with banaba extract. Any weight claim on a label is unsupported.

Dosage & safety

Studied doseHuman studies used 32-48 mg/day of banaba leaf extract standardized to 1% corosolic acid, or 10-32 mg/day of corosolic acid directly, usually split before meals for 2-4 weeks. Commercial products commonly supply 200-500 mg of leaf extract; check the corosolic acid percentage, since that is the only figure comparable to the trials.
SafetyNo serious adverse effects have been reported in the small controlled human trials or in animal toxicology, and reviews describe it as well tolerated. The realistic risk is additive hypoglycaemia when combined with insulin, sulfonylureas, metformin or other glucose-lowering supplements — monitor blood glucose and adjust with your prescriber, never on your own. Corosolic acid has been linked to renal effects at high doses in animals; avoid with impaired kidney function. No data in pregnancy, breastfeeding or children. It is not a replacement for diabetes medication.

How to take it

TimingSplit the dose and take it just before carbohydrate-containing meals.
With food?Immediately before the meal.
Worth knowingCompare products on corosolic acid milligrams rather than extract weight — that is the only figure comparable to the trials.

Interactions

With medications

  • insulin, sulfonylureas and metformin

    Additive blood-glucose lowering that can tip into hypoglycemia. monitor glucose and adjust medication only with your prescriber

With other supplements

  • other glucose-lowering supplements (berberine, alpha-lipoic acid, salacia, cinnamon)

    Additive hypoglycemia risk. use one at a time

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does banaba leaf lower blood sugar?

Banaba leaf has limited evidence for lowering blood glucose: small, mostly industry-run studies using corosolic acid for 2-4 weeks reported roughly 5-30% reductions in fasting or post-meal glucose. None used HbA1c as a properly powered endpoint, so banaba is not a diabetes treatment.

How much banaba leaf extract should I take?

Human studies of banaba used 32-48 mg/day of extract standardized to 1% corosolic acid, or 10-32 mg/day of corosolic acid, split and taken just before carbohydrate-containing meals. Compare products on corosolic acid content, since many sell 200-500 mg of leaf extract with no comparable figure.

Does banaba help with weight loss?

No controlled human trial shows meaningful fat loss with banaba extract (limited evidence); anti-obesity effects appear only in rodents. Any weight-loss claim on a banaba label is unsupported.

Can I take banaba with metformin or insulin?

Banaba can add to insulin, sulfonylureas and metformin and tip you into hypoglycemia, so monitor glucose and adjust medication only with your prescriber. Avoid stacking banaba with other glucose-lowering supplements, and avoid it with impaired kidney function.

Scientific references

Where to buy

Vitacost, Banaba Leaf Extract, 300 mg, 120 Capsules

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