Green tea compound may improve blood glucose tolerance


A compound found in green tea improves glucose tolerance and increases insulin secretion in laboratory mice with diabetes, according to the journal Nutrition & Metabolism.

Researchers from Karolinska Institutet in Sweden separated the diabetic mice into two groups. They fed the first group a green tea extract that has a high content of epigallocatechin gallate (EGCG), a type of polyphenol. The remaining mice served as the control group.

Throughout the ten-week study, researchers measured fasting blood glucose, body weight and food intake. After ten weeks, they measured glucose and insulin levels during an oral glucose tolerance test.

It also found that EGCG supplemetation reduces the number of pathologically changed islets of Langerhans, specialized cells in the pancreas that make and secrete hormones. Insulin-producing beta cells are just one of five types of cells in an islet.

Changes in the islets of Langerhans are typically associated with the onset of diabetes.

The study showed that EGCG increases the number and size of islets and heightens pancreative endocrine area.

“This study shows that the green tea extract EGCG markedly preserves islet structure and enhances glucose tolerance in genetically diabetic mice,” wrote the researchers in the study.

“Dietary supplementation with EGCG could potentially contribute to nutritional strategies for the prevention and treatment of type 2 diabetes,” they wrote.

EGCG is one of four main polyphenols found in fresh tea leaves. The other three are epogallocatechin, epicatechin gallate, and epicatechin.

Green tea contains 30 to 40 percent water-extractable polyphenols. Black tea, which is green tea oxidized by fermentation, contains 3 to 10 percent. Oolong tea is semi-fermented tea and falls halfway between green and black teas in terms of polyphenol levels.

Green tea has long been a suggested therapy for diabetes, but the mechanisms behind it are not well understood.

Green tea is purported to reduce the risk of Alzheimers disease and certain cancers, according to It’s also said to improve cardivascular and oral health and help with weight management.

Sources: Nutrition & Metabolism,,

photo by John Nyboer


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