Stevia is a plant native to South and Central America. It has been used as a traditional diabetes remedy for decades. Because refined stevia is 250 to 300 times sweeter than sugar and doesn't increase blood sugar levels, it is a popular sugar substitute for people with diabetes. But this plant's benefits might extend beyond its sweet taste -- stevia is touted to influence the hormone insulin, which helps the body use and store sugar. Limited animal research indicates stevia may increase insulin production and improve insulin action. However, larger studies on humans are needed to fully understand how stevia affects insulin in the body.
Stevia Use in Diabetes
Stevia, derived from the plant species Stevia rebaudiana, is well known as a sweetener. The compounds that provide the characteristic sweetness -- stevioside and rebaudioside -- are from the plant's leaves. The whole leaf, dried leaves and powders are sold as dietary supplements, a category in which proof of safety is not requires; the Food and Drug Administration (FDA) did not approve these forms for use as a sweetener. Stevia leaf extract, a highly refined form of stevia, has received FDA approval to be used as a sweetener in the U.S. However, because of the lack of quality human research trials, the FDA has not approved any health claims on stevia related to its effect on insulin levels or blood sugar control.
Aside from sweetener use, interest in stevia as a therapy for diabetes has prompted research into the effects of stevia or its components on insulin. A study reported in the January 2002 issue of "Phytomedicine" compared glucose levels in diabetic rats after an infusion of either glucose only or glucose and steviocide. The stevia compound was noted to improve blood sugars, and researchers noted increased insulin levels in these rats and decreased levels of glucagon -- a hormone that increases blood sugar levels. A paper published in the October 2015 issue of "Phytomedicine" used cells derived from mice and indicated that steviocide may lower blood sugar by mimicking the effects of insulin. Steviocide may also lower blood sugar by improving insulin action, as reported in a study of diabetic rats that was published in the October 2005 issue of "Hormone and Metabolic Research."
Limited human studies have been done regarding the impact of stevia on insulin. In an article published in the January 2004 issue of "Metabolism," subjects with type 2 diabetes experienced a decrease in post-meal blood sugars after a dose of stevioside with a test meal. The control group received a dose of cornstarch with a test meal. Although insulin levels were not significantly increased after either test meal, the authors suggest that steviocide may help increase insulin secretion in response to blood sugar levels. According to a concern outlined in the October 2007 "British Journal of Clinical Pharmacology," cornstarch is not a reliable placebo in these types of studies because it can decrease post-meal glucose levels. Because this study also included relatively few subjects, it is difficult to draw any firm conclusions. Larger clinical trials are necessary to more definitively understand the relationship between stevia and insulin.
Warnings and Precautions
Stevia's effect on insulin can only be postulated, because available study results are preliminary and need to be validated with larger quality human studies. In addition, the FDA failed to approve dried or powdered stevia leaves for use as a sweetener because animal studies have raised concerns about their potential effects on reproductive organs, the kidneys and the cardiovascular system. The American Diabetes Association's clinical practice guidelines discuss stevia only in regard to sweetener use, and outline that when used appropriately, stevia and other zero- or low-calorie sweeteners may help with weight loss or weight control. It may be wise to use stevia sweetener in moderation, and discuss any plans to use whole or dried leaves with your diabetes care team. Always be sure to ask your healthcare provider about any supplements you are considering, and never discontinue or adjust the dose of any prescribed medication without your healthcare provider's approval.