If you live in the southern part of the US, you are probably familiar with Lagerstroemia indica. Commonly known as crape myrtle, its colorful flowers and graceful trunks make it a popular landscaping tree.
In tropical areas of Asia, Lagerstroemia speciosa, a related species, is more than a pretty tree. Throughout this region, this plant has a long history of use in traditional medicine for a variety of ailments—including diabetes.
Banaba Leaf for Blood Sugar Control
One of the earliest scientific papers on Lagerstroemia speciosa was written in 1941 by Faustino Garcia, who referred to it as banaba, as it is called in the Tagalog language of his native Philippines.
In this paper, he described an “insulin-like principle” in banaba leaves. As you know, your body needs insulin for blood sugar control. When glucose (sugar) levels in the blood rise—as they do after your digestive tract breaks down the food you eat—your pancreas releases insulin. Insulin signals your cells to let glucose enter, where it is used to produce ATP, the energy that fuels your body. Banaba leaf simply enhances your body’s ability to respond to insulin, move glucose into your cells, and keep blood sugar in the normal range.
Banaba’s “insulin-like principle” has been confirmed in multiple animal studies. A number of small human studies have also had positive results. Although most of them reported decreases in blood sugar in the 10%–20% range, one clinical trial found that patients with type 2 diabetes who took 48 mg of a standardized banaba leaf extract daily for 15 days had a 30% reduction in blood sugar!
Other clinical trials have reported enduring reductions in fasting blood glucose and A1C when banaba extract was used for longer periods, up to one year.
How Does Banaba Extract Work?
Like all plants, banaba contains an array of natural compounds. They include ellagitannins, members of the polyphenol family of phytonutrients that contribute to banaba’s antioxidant and anti-inflammatory properties. Another important constituent, which is believed to be primarily responsible for banaba’s therapeutic effects on blood sugar, is corosolic acid.
Corosolic acid works on several fronts to improve blood sugar control:
- Decreases insulin resistance by increasing the sensitivity of insulin receptors, making it easier for cells to respond to insulin’s signals and move glucose out of your bloodstream and into your cells where it’s used for energy.
- Enhances the activity of GLUT4 proteins, which help transport glucose into your cells.
- Decreases the production of glucose in the liver, which helps reduce blood sugar levels.
- Inhibits alpha-glucosidase, an enzyme that breaks down starches and other carbohydrates into glucose, leading to a decrease in blood sugar.
Additional Benefits for Diabetes
Emerging research suggests that banaba leaf also addresses other health challenges that are of particular concern for individuals with diabetes, prediabetes, and metabolic syndrome. Extracts have significantly improved lipid levels and obesity in animal studies, and although human research is limited, results are promising.
One clinical trial tested banaba in combination with other botanicals and nutrients, including berberine, chromium, and curcumin, in patients with elevated fasting blood sugar. The results were impressive—a 34.7% reduction in triglycerides, 13.7% increase in HDL cholesterol, plus improvements in fasting glucose and insulin sensitivity.
This study used a supplement with a combination of ingredients, so benefits cannot be attributed to banaba alone. Yet, it does support the advantages of a multi-ingredient approach that works on multiple mechanisms and risk factors.
Animal studies have shown that banaba reduces weight gain and fat accumulation as well. The reason, according to a 2019 lab study, is because corosolic acid inhibits lipogenesis (the conversion of glucose and other carbohydrates into fat) and adipogenesis (the formation of adipocytes, or fat cells, from stem cells).
I am not suggesting, based on this early research, that banaba leaf will help you lose weight. Yet, because obesity is a risk factor for type 2 diabetes—and the majority of people who have diabetes struggle with their weight—a therapy that enhances blood sugar control and may also help stave off weight gain is a winner in my book.
Safe, Fast & Effective
Virtually all of the research on banaba leaf has concluded that it has an excellent safety profile and is well tolerated, even in large doses. It also gets to work quickly. Studies suggest that it exerts its positive effects on blood sugar within 60 minutes of taking it.
Banaba leaf extract is available in several concentrations, but one of the better studied extracts is standardized for 18% corosolic acid. The suggested dose is 48 mg, preferably taken in divided doses about 30 minutes before meals. It may be used in combination with other supplements that target optimal blood sugar control.