July 2013

Green Tea May Benefit Blood Sugar and Insulin Levels

Green tea may have positive effects on glucose control and insulin sensitivity, a study reports.

Green tea is made from the leaves of Camellia sinensis, an evergreen shrub native to Southeast Asia. Both green tea and black tea are made from the same plant species. Green tea is produced by lightly steaming the leaves. Black tea is produced by allowing the leaves to ferment. Green tea is rich in the class of polyphenol compounds known as catechins. Polyphenols may have health benefits for humans. Many of the effects of green tea are thought to be due to its most abundant catechin, epigallocatechin gallate (EGCG).

Diabetes, also known as diabetes mellitus, is a chronic health condition where the body is unable to produce enough insulin and properly break down sugar (glucose) in the blood. Glucose comes from food and is used by the cells for energy. Glucose is also made in the liver. Insulin is a hormone produced by the pancreas, a large gland behind the stomach. Insulin is needed to move sugar into the cells where it can be used for energy needed for body processes. With Type 1 diabetes, the body does not make any insulin. With Type 2 diabetes, the more common type, the body does not make or use insulin properly. Without enough insulin, glucose stays in the blood and causes a condition called hyperglycemia, or high blood sugar levels.

In the current study, researchers analyzed the available literature for evidence supporting the use of green tea in improving glucose control and insulin sensitivity. They included 17 high-quality trials conducted among 1,133 people. All of the studies looked at the possible effects of green tea on blood sugar and insulin levels.

The results suggested that the consumption of green tea may significantly lower fasting blood sugar and fasting insulin concentrations.

The authors concluded that their analysis suggests that green tea may favorably impact blood sugar and insulin levels. More research is needed to confirm these findings.

In addition to green tea, numerous integrative therapies have been evaluated for possible benefit in people with diabetes and related conditions. There is strong scientific evidence supporting the use of alpha-lipoic acid for diabetes type 2 and the use of konjac glucommanan for diabetes.

For more information about green tea, please visit Natural Standard's Foods, Herbs & Supplements Database.


  1. Liu K, Zhou R, Wang B. Effect of green tea on glucose control and insulin sensitivity: a meta-analysis of 17 randomized controlled trials. Am J Clin Nutr. 2013 Jun 26. [Epub ahead of print] 
  2. Natural Standard: The Authority on Integrative Medicine. 

The information in this brief report is intended for informational purposes only, and is meant to help users better understand health concerns. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions. Copyright © 2023 NatMed. Commercial distribution or reproduction prohibited. NatMed is the leading provider of high-quality, evidence-based, clinically-relevant information on natural medicine, dietary supplements, herbs, vitamins, minerals, functional foods, diets, complementary practices, CAM modalities, exercises and medical conditions. Monograph sections include interactions with herbs, drugs, foods and labs, contraindications, depletions, dosing, toxicology, adverse effects, pregnancy and lactation data, synonyms, safety and effectiveness.