Native to the forests of India, Gymnema sylvestre (also called gumar) has a coincidental double relationship to sugar: When placed on the tongue, it blocks the sensation of sweetness, and when taken internally, it might help control blood sugar levels in people with diabetes. (There doesn’t seem to be any connection between these two uses.)

Practitioners of Ayurveda(the traditional medicine of India) first used gymnema to treat diabetes almost 2,000 years ago. In the 1920s, preliminary scientific studies found some evidence that gymnema leaves can reduce blood sugar levels,1 but nothing much came of this observation for decades. Research in India picked up again in the 1980s and 90s, leading to the publication of promising preliminary studies in people.

Gymnema has become increasingly popular in the United States as a supportive treatment for diabetes. However, the evidence that it works remains weak. Only double-blind, placebo-controlled studies can prove a treatment effective, and none have yet been reported for gymnema. Current evidence is limited to a few animal studies and human open trials.2-9 (For information on the importance of the double-blind design, see "Why Does This Database Rely on Double-blind Studies?")

Warning: This herb is advocated as a support to standard treatment, not as a replacement for it. Gymnema definitely cannot be used as a substitute for insulin treatment, and has not been proven strong enough for use in lieu of oral diabetes medications. However, there are also potential risks involved in adding gymnema to an existing treatment regimen. See Safety Issues.