Gymnema

NATURAL PRODUCTS

Gymnema sylvestris

Gymnema sylvestris leaves have been found to cause hypoglycemia in laboratory animals and have found a use in herbal medicine to help treat adult onset diabetes mellitus (NIDDM). The active glucose lowering components of the plant are the gymnemic acids. These compounds also have been found to increase fecal excretion of cholesterol, but further studies will be required to prove whether this effect will have any clinical significance in treating hypercholesterolemia (high serum cholesterol). Other uses for gymnema leaf extract include its ability to act as a laxative, diuretic, and cough suppressant. These other actions would be considered adverse reactions when gymnema is used for its glucose lowering effect in diabetes.

Gymnema leaf extract, notably the peptide Gurmarin component, has been found to interfere with the ability of the taste buds on the tongue to taste sweet and bitter. Gymnemic acid has a similar effect. It is believed that by inhibiting the ability to taste sweetness, people taking it will not eat as much sweetened foods, and this activity may be partially responsible for its hypoglycemic effect.

There are several other ways gymnema lowers blood sugar but research has yet to elucidate which mechanism is primarily responsible for the effect. The gymnemic acid components are believed to block the absorption of glucose in the small intestine, but the exact mechanism is unknown. This action is apparently different than the prescription drug acarbose (Precose), an alpha glucosidase inhibitor, that delays the intestinal absorption of glucose by blocking the absorption of disaccharides, dextrin, and starches. Another study concluded that the extract of the plant leaf stimulated insulin hormone secretion from the Beta cells of the pancreas, but added that the extract may also increase glucose uptake in cells throughout the body by increasing their permeability to insulin. These two effects are also similar to the actions of other prescription antidiabetic drugs, but the pharmacological mechanisms used by gymnema are unknown. Prescription sulfonylurea drugs increase the secretion of insulin from the Beta cells of the Islet of Langerhans in the pancreas of adult onset (NIDDM) diabetes patients.

One of the mechanisms responsible for adult onset diabetes mellitus is a form of insulin resistance, which is attributed to the inability of insulin to enter cells via the insulin receptor. Gymnema may be active in this regard, by overcoming the resistance, but it will take further studies to see whether this is the mechanism and whether the effect is clinically relevant. Should this effect be proven, gymnema may prove useful in both adult onset (NIDDM) and juvenile onset diabetes mellitus (IDDM) to help insulin enter cells. In the case of IDDM, the insulin is injected by syringe and is not secreted from the pancreas. The prescription drug, Avandia (rosiglitazone), acts by blocking insulin resistance at the cell, thus increasing the cells’ permeability to insulin and allowing it to enter the cell and have its desired effect on the uptake, utilization, and storage of glucose, fatty acids, and amino acids.

Gymnema is not a substitute for traditional medical care for diabetes, but may be a supplement to current antidiabetic therapy under the direct care of a healthcare professional responsible for their primary diabetes management. It is not a substitute for current antidiabetic medications.

Drug interactions with gymnema extract are unknown, but it is likely that it will be additive to other antidiabetic medications the person is taking. Whether this interaction will require a dosage adjustment of current medications will require further study. And whether the laxative effect will also have an effect on the absorption and therapeutic response of other drugs being taken concurrently is unknown.

As in other natural products, there is a quality control issue, where the actual dosage of each lot of product may vary. Standardized products using the same extraction techniques will help with this problem. However, the effective dose will vary between people, and dosage adjustment will require the knowledge of a diabetic management professional. Some studies have used a daily dose of 400 mg of gymnemic acids, from the water soluble fraction, and have found it to be effective alone in some patients with non-insulin dependent diabetes mellitus. But the most appropriate dose is unknown and a majority of patients had to continue their regular diabetic medications. Since there have been no formal dose ranging studies, a minimum and maximum effective and safe dose is unknown. Gymnema containing products should only be used under the supervision of a qualified healthcare practitioner who is responsible for the patient’s diabetes management and familiar with the patient’s medical and drug histories. Based on the actions of the herbal extract, gymnema may very well fall under the category of being an unapproved drug.

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This page was last updated on 04/29/05.