Insulin plant (Costus pictus) is the subject of numerous studies from the National Institute of Health for its effects on – you guessed it – hyperglycemia and diabetes. It has a history of use in India and other countries, as well as a lot of modern trials confirming its medicinal use to balance blood sugar.
Please note, there are at least two other species of Costus used in similar but distinct ways, and all may be referred to as Insulin Plant. Be sure you are working with the precise species you are intending to! Cross reference for safety.