Gymnema sylvestre:

Gymnema sylvestre (GS) is a woody climbing plant that grows in the tropical forests of central and southern India. The leaves are used in herbal medicine preparations. Gymnema sylvestre is known as "periploca of the woods" in English and mesbasringi (meaning "ram's horn") in Sanskrit. The leaves, when chewed, interfere with the ability to taste sweetness, which explains the Hindi name gurmar - "destroyer of sugar."
Plant constituents include two resins (one soluble in alcohol), gymnemic acids, saponins, stigmasterol, quercitol, and the amino acid derivatives betaine, choline and trimethylamine.
Gymnema sylvestre is a stomachic, diuretic, refrigerant, astringent, and tonic. It has been found to increase urine output and reduce hyperglycemia in both animal and human studies.
Gymnema sylvestre has been used in India for the treatment of diabetes for over 2,000 years. The primary application was for adult-onset diabetes, a condition for which it continues to be recommended today in India. The leaves were also used for stomach ailments, constipation, water retention, and liver disease.
Extracts of Gymnema sylvestre given to patients with type I diabetes on insulin therapy reduces insulin requirements and fasting blood sugar levels, and improves blood sugar control. In a study of type II diabetics, Gymnema sylvestre extract given along with oral hypoglycemic drugs was shown to improve blood sugar control and to either lead to discontinuation of the medicine or a significantly reduced dosage. Gymnema sylvestre is interesting to note that Gymnema sylvestre extract given to healthy volunteers does not produce any blood sugar-lowering, or hypoglycemic, effects.

Blood Sugar:
The main focus of Gymnema sylvestre research is blood sugar regulation and glucose metabolism. Gymnema sylvestre has been used in India for treatment of diabetes for about 2000 years. Today in India it is being used to treat primarily type II diabetes and type I as well. The herb has shown to reduce blood sugar, glycosylated haemoglobin and glycosylated plasma proteins when used for 18-20 months [1]. The effect is gradual rather than immediate with conventional drugs. The active components responsible for lowering glucose are the gymnemic acids.
Weight Loss :
I was intrigued when I read how gymnema could reduce and alter the taste of sugar, and it does just that. By placing the herb on your tongue or drinking the tea, the perception of sugar or aspartame is reduced or eliminated completely. That may come in handy if you want to deter a binge on chocolate cheesecake. Some articles state that this is not true so I tried it myself by breaking open a capsule and placing a small amount in my mouth. Gymnema sylvestre did indeed eliminate the perception of sugar. The effect lasted for about 15 minutes as I sampled other foods and drinks. Sweet Relief gum is available which contains gymnema.
Gymnema sylvestre is also said that the herb reduces cravings for sugars. More research needs to be done on that statement. Some believe that the sugar taste blocking feature has a factor in not only the reduction in cravings, but the hypoglycemic reactions as well.
Gymnema sylvestre may interact with medications taken to lower blood sugar levels resulting in hypoglycemia.
Side Effects for Gymnema sylvestre:

There are no side effects listed at the time of writing this feature (3/2002). Only those which seem to be connected with hypoglycemia. Adverse effects reported to the FDA appear to be mainly blends containing Gymnema sylvestre targeted for weight loss or energy.