Banaba is a medium-sized tree. Its leaves have been used to treat diabetes in folk medicine for centuries.
In addition to their anti-diabetic properties, banaba leaves offer health benefits, such as antioxidant, cholesterol-lowering, and anti-obesity effects.
Banaba, or Lagerstroemia speciosa, is a tree native to tropical Southeast Asia. It belongs to the genus Lagerstroemia, also known as Crape Myrtle.
The tree is widely distributed in India, Malaysia, and the Philippines, where it’s known as Jarul, Pride of India, or Giant Crape Myrtle.
Almost every part of the tree offers medicinal properties. For example, the bark is often used to treat diarrhea, while its root and fruit extracts are believed to have an analgesic, or pain-relieving, effect.
The leaves contain over 40 beneficial compounds, of which corosolic acid and ellagic acid stand out. Though the leaves offer a variety of benefits, their ability to lower blood sugar levels appears the most potent and sought after.
Research suggests that banaba leaves have various medicinal properties.
The antidiabetic effect of banaba leaves is one reason why they’re popular.
Researchers attribute this effect to several compounds, namely corosolic acid, ellagitannins, and gallotannins.
Corosolic acid lowers blood sugar levels by increasing insulin sensitivity, enhancing glucose uptake, and inhibiting alpha-glucosidase — an enzyme that helps digest carbs.
That’s why it’s claimed to have an insulin-like effect.
Insulin is the hormone that regulates blood sugar levels. In people with type 2 diabetes, insulin resistance increases the demand for this hormone.
However, the pancreas may not be able to meet those demands, resulting in high blood sugar levels .
In one study in 31 adults, those who received a capsule containing 10 mg of corosolic acid had lower blood sugar levels for 1–2 hours after performing an oral glucose tolerance test, compared with those in a control group.
In addition to corosolic acid, ellagitannins — namely lagerstroemin, flosin B, and reginin A — also improve blood sugar levels.
They promote glucose uptake by activating glucose transporter type 4 (GLUT4), a protein that transports glucose from the bloodstream into muscle and fat cells.
Likewise, gallotanins seem to stimulate the transportation of glucose into cells.
It’s even hypothesized that a type of gallotanin called penta-O-galloyl-glucopyranose (PGG) has higher stimulatory activity than corosolic acid and ellagitannins.
While studies have found promising results on the anti-diabetic properties of banaba leaves, most have used a combination of herbs or compounds.
Thus, further studies on the leaves alone are needed to better understand their blood sugar-lowering effects.
Antioxandant are compounds that counteract the harmful effects of free radicals.
These effects could otherwise negatively affect DNA, fat, and protein metabolism and promote disease.
Furthermore, antioxidants protect your pancreas from free-radical damage an additional anti-diabetic effect.
Banaba leaves can neutralize free radicals due to their high content of antioxidants like phenols and flavonoids, as well as quercetin and corosolic, gallic, and ellagic acids.
One 15-day study in rats found that 68 mg per pound (150 mg per kg) of body weight of banaba leaf extract neutralized free radicals and other reactive species while regulating levels of antioxidant enzymes.
Still, human studies on the antioxidant effects of banaba leaves are lacking.
Obesity affects about 40–45% of American adults, and it’s a risk factor for chronic disease.
Recent studies have linked banaba leaves with anti-obesity activity, as they may inhibit adipogenesis and lipogenesis the formation of fat cells and fat molecules, respectively
Also, polyphenols in the leaves, such as pentagalloylglucose (PGG), may prevent fat cell precursors from transforming into mature fat cells.
However, most research on this topic was conducted in test tubes, so human studies are needed.
High blood cholesterol is a key risk factor for heart disease — the leading cause of death in America and third leading cause of mortality worldwide.
Animal and human studies suggest that corosolic acid and PGG in banaba leaves may help lower blood cholesterol and triglycerides levels.
In one 10-week study in mice fed a high cholesterol diet, those treated with corosolic acid showed a 32% reduction in blood cholesterol and a 46% reduction in liver cholesterol levels, compared with a control group.
Similarly, a 10-week study in 40 adults with impaired fasting glucose found that a combination of banaba leaf and turmeric extracts reduced triglyceride levels by 35% and increased HDL (good) cholesterol levels by 14%.
While these results are promising, research on the direct effects of banaba leaves on blood cholesterol levels is still needed.
Both animal and human studies agree that the use of banaba leaves and their extracts as herbal remedies appears to be safe.
However, their blood-sugar-lowering abilities may have an additive effect that could lower your blood sugar levels too much when taken with other diabetic drugs like metformin, or with other foods used to lower blood sugar levels like fenugreek, garlic, and horse chestnut.
Also, people with known allergies to other plants from the Lythraceae family such as pomegranate and purple loose strife should use banana-based products with caution, as these individuals may have an increased sensitivity to this plant.
What’s more, a study in an adult with diabetes and impaired kidney function reported that corosolic acid from banaba leaves may lead to kidney damage when taken with diclofenac.
Diclofenac is a nonsteroidal anti-inflammatory drug (NSAID) used to treat joint pain, and corosolic acid may impair its metabolism. Plus, corosolic acid could favor lactic acid production, leading to severe lactic acidosis — a cause of concern in people with kidney disease.
Therefore, be sure to consult your healthcare provider before taking any banaba leaf product, especially if you have an underlying health condition.
Banaba leaves are primarily consumed as a tea, but you can also find them in powder or capsule form.
As for the dosage, one study suggested that taking 32–48 mg of banaba leaf extract capsules standardized to contain 1% corosolic acid for 2 weeks may reduce blood sugar levels.
However, more research is needed to determine the proper dosage. Therefore, it’s best to follow the instructions on the specific supplement you choose to take.
When it comes to the tea, some claim you may drink it twice per day. However, there’s no scientific evidence to support this dosage.
Banaba leaves are renowned for their ability to lower blood sugar levels.
In addition, they’ve been shown to improve risk factors for heart disease and provide antioxidant and anti-obesity activity.
Research suggests that these leaves are a safe herbal remedy. To take advantage of their benefits, you can drink banaba leaf tea or take them in capsule or powder form.
Nevertheless, take into account that their blood-sugar-lowering effects may add up with those of conventional diabetic drugs. Thus, taking both could lower your blood sugar levels too much.
As with any supplement, speak with your healthcare provider before starting a new routine.