Banaba Leaf Extract
Banaba (Lagerstroemia speciosa L.) is a herbal medicine used to treat diabetes in some countries such as Philippines. It is consumed in the form of tea, juice or dietary supplement. Banaba extract is high in corosolic acid, plant insulin, suggested to have anti-diabetic effect.
Scientific evidence that supports its use in treatment of diabetes on humans is scarce. Nonetheless, there are some researches on animals that indicate banaba leaf extract may play a role in the treatment of diabetes, by affecting factors (such as blood glucose level) that are associated with the developement of diabetes. For instance, studies on mice report that banaba leaf extract reduced blood glucose, significantly increased insulin sensitivity and improved hyperglycemia, lowered hepatic lipid contents and triglycerides in genetically diabetic mice. The decrease in blood glucose was possibly due to increase in the uptake of glucose. In another mice study, banaba extract did not have significant effect on blood glucose level.
A review of animal and human studies on the effect of banaba leaf extracts and corosolic acid, one of the main active chemicals in banaba leaf, summed up that banaba leaf increased the rate of blood glucose removal, reduced the rate of conversion of sucrose and starch and other non-carbohydrates into glucose. The same review study also reported that no side effects of banaba leaf were found.
Banaba is also reported to aid in weight loss. At least in one study, banaba extract fed mice lost more weight that the control group. Other suggested health benefits of banaba leaf extract, according to studies on diabetic mice, include lowering of blood cholesterol (hypocholesterolemic) and fatty acid (hypolipidemic) levels due to dietary sources. This hypocholesterolemic and hypolipidemic effect is attributed mainly to the corsolic acid banaba is known to contain in high amounts. Banaba may also have antioxidant elements that can fight free radicals.
Mi-Young Park, Kwang-Seung Lee, and Mi-Kyung Sung. 2005. Effects of dietary mulberry, Korean red ginseng, and banaba on glucose homeostasis in relation to PPAR-alpha, PPAR-gamma, and LPL mRNA expressions. Life Sciences, 77(26): 3344-3354.
Takagi S, Miura T, Ishihara E, Ishida T, Chinzei Y. (2010). Effect of corosolic acid on dietary hypercholesterolemia and hepatic steatosis in KK-Ay diabetic mice. Biomed Res. 31(4):213-8.
Saumya SM, Basha PM. (2010). Antioxidant effect of Lagerstroemia speciosa Pers (banaba) leaf extract in streptozotocin-induced diabetic mice. Indian J Exp Biol. 49(2):125-31.
Sidney J. Stohs, Howard Miller and Gilbert R. Kaats (2012). A Review of the Efficacy and Safety of Banaba (Lagerstroemia speciosa L.) and Corosolic Acid. Phytotherapy Research 26(3): 317-324.
Suziki Y, Unno, T., Ushitani, M., Hayashi, K., and Kakuda, T. 1999. Anti-obesity activity of extracts from Lagerstroemia speciosa L. (banaba) leaves on female KK-Ay mice. J Nutr Sci Vitaminol ( Tokyo ), 45(6):791-5.