Green Tea Lowers Diabetes Risk, Transdermal Catechin Delivery Effective

OSAKA, Japan & PISCATAWAY, N.J.--High intake of green tea may inhibit risk of Type 2 diabetes, and transdermal tea delivery may improve bioavailability of its most studied catechin, epigallocatechin-3-gallate (EGCG), according to studies published in the Annals of Internal Medicine (144, 8:554-62, 2006) and The Journal of Pharmacy and Pharmacology (58, 5:599-604, 2006), respectively.

Over a five-year period, researchers from Osaka University and Osaka City University looked for a relationship between consumption of green tea and other beverages on development of Type II diabetes in 17,413 individuals (6727 men and 10,686 women; 40 to 65 years of age) from 25 communities across Japan, who had no history of the disease. There were 444 self-reported new cases of physician-diagnosed diabetes in 231 men and 213 women. Consumption of green tea was inversely associated with risk for Type II diabetes after adjustment for age, sex, body mass index, and other risk factors. Further, total caffeine intake from green tea was associated with a 33-percent reduced risk of developing the disease. These inverse associations were more pronounced in women and overweight men.

Additionally, scientists from The State University of New Jersey used a rodent model to demonstrate transdermal delivery of tea extract may improve absorption of EGCG, which they noted has a typically low bioavailability in men and rodents. Application of 50 mg/kg EGCG as a transdermal gel to SKH-1 mice resulted in higher plasma concentrations of EGCG in the animals than those previously reported for oral administration of the compound. Further, stability studies showed that the transdermal formulation was stable at 4°C and had a half-life of 47.1 and 20.2 hours at 25°C and 37°C, respectively. The researchers concluded transdermal EGCG is useful for delivering prolonged levels of EGCG to plasma and tissues, and may provide an alternative to tea consumption as a dosage form of EGCG.