A handful of scientific reports published in the last few years indicate that green tea, and in particular the catechin, EGCg (which it contains in high concentrations), may be effective in preventing or treating diabetes (especially the type-2 variety). This is great news for avid tea drinkers, but it is even better news for those who use whole green tea leaves as a culinary ingredient since EGCg is present in concentrations which are much higher in whole leaves than in brewed green tea. This is confirmed by a report issued by the USDA which states that EGCg is contained in whole green tea leaves at a concentration which is 100 times greater than in brewed green tea.
Green tea’s anti-diabetic properties were investigated in a report published in the Journal of Ethnopharmacology in 2002 with positive results. After inducing diabetes in laboratory rats, the researchers attempted to see if their blood conditions could be returned closer to normal by administering green tea to some of the rats. After several days of treating one group of the rats with green tea, the researchers found that their blood was closer to normal than the control group who were simply given filtered water.
Another study published in 2006 found similar results in humans. This population-based study followed the coffee and tea consumption of over 17,000 people living in Japan. At the beginning of the study none of these individuals had diabetes. After five years, the participants were asked to complete a survey in which they, among other things, listed the amount of coffee or tea that they drank each day and if they had been diagnosed by a doctor with type two diabetes. After adjusting the data for irrelevant factors, the researchers found that the consumption of large amounts of coffee or green tea was associated with a reduced chance of developing type two diabetes. Black tea and oolong tea seemed to have no effect. The researchers did not arrive a conclusive evidence about which element in green tea was responsible for the change, although it should be noted that both green tea and coffee contain caffeine.
However, another study conducted in the same year attempted to analyze green tea’s anti-diabetic capacity devoid of caffeine. In this study, researchers demonstrated the ability of isolated EGCg (the primary compound present in green tea) to reduce glucose levels in the blood stream in a way that is in some ways similar to insulin, although acting much more slowly. This study was conducted in a laboratory setting using heptoma cells from rats. The researchers treated these cells in two separate batches with either insulin or EGCg and then compared the glucose production of both samples. In the final analysis, the researchers determined that EGCg was effective in lowering glucose levels. While they stress that it is still not clear what role green tea may play in the prevention or treatment of diabetes, it is encouraging that these results seem to confirm other findings such as those cited above. This study also shows that not all of green tea’s anti-diabetic effects can be attributed to caffeine.
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“Republished with permission from EatGreenTea.com, the original edible green tea.”