Effect of an Extract of Green Tea on Adults With Type 2 Diabetes

Background: Recent evidence suggests that tea from Camellia Senensis (e.g., green, oolong and black tea) may have a hypoglycemic effect.

Objective: We evaluated the ability of an extract of green and black tea to improve glucose control over a three month period using a double blinded randomized multiple dose (either placebo, 375mg or 750mg) study in adults in with Type 2 Diabetes.

Patients: The 49 subjects who completed this study were predominantly whites with an average age of 65, a median duration of Diabetes of 6 years, and 80% reported using hypoglycemic medication.

Measurements: HbA1c at three months was the primary endpoint. Results: After three months the mean changes in HbA1c were +0.4, +0.3 and +0.5, in the placebo, 375mg and 750mg arms, respectively. The changes were not significantly different between study arms.

Limitations: Evaluation of a particular extract that contained components of black teas as well as green tea. Power insufficient to detect changes in HbA1c < 0.5.

Conclusions: We did not find a hypoglycemic effect of extract of green tea in adults with Type 2 Diabetes, but cannot rule out the possibility that tea may have a small beneficial effect.

Inclusion criteria

• Adults with Diabetes not taking insulin

Exclusion criteria

• pregnancy, warfarin therapy