Corosolic acid, found in a banaba leaf, is reported to decrease blood sugar levels within 60 minutes. This occurs by improving the insulin pathways. Corosolic acid can also act as an insulin sensitizer and enhance glucose transportation. However, if you consume a nutritious, balanced diet, you will likely not need to take any supplements, including banaba. Supplements are not regulated and their efficacy and safety are not supported by solid evidence, so always speak with a healthcare provider prior to adding a product to your routine.