Green Tea, Caffeine, and Risk of Diabetes.




Annals of Internal Medicine

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Consumer Data: Green Tea Diabetes Mellitus, Type 2
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Green tea has long been used in much of the world as a popular beverage and a respected medicinal agent. Early Chinese medical literature lists green tea as an agent to promote digestion, improve mental faculties, decrease flatulence and regulate body temperature. The earliest known record of use dates back to around 2700 B.C. Today, ceremonies, celebrations, relaxation time and ordinary meals usually consist of tea in most parts of the world, except where coffee has become the more popular beverage, like the United States.

Green tea has antioxidant properties. This means it has the ability to protect against oxidative damage to tissues and red blood cells. Though debated, it is important to note that some studies suggest that adding milk to green tea significantly decreases its antioxidant potential.1

Recently, a study was published regarding green tea and caffeine intake and risk of Type 2 Diabetes. The authors stated that in the western hemisphere, coffee intake is associated with lower risk of diabetes. The effect of green, black or oolong teas are not known. Taking place in Japan, this study involved over 17,000 healthy individuals aged 40-65 years of age. There was a 5-year follow-up period where these individuals completed self-administered questionnaires regarding tea and coffee intake and diagnosed diabetes. During this 5-year period, there were 444 cases of diabetes reported. The results showed that intake of green tea and coffee was associated with a decreased risk of diabetes. Those drinking 6 or more cups of green tea or 3 or more cups of coffee had a reduction in risk compared to those drinking less than one cup a week. The association was not seen in black or oolong teas. The authors concluded that, “Consumption of green tea, coffee, and total caffeine was associated with a reduced risk for type 2 diabetes.”2


1. Hertog MG, et al. Antioxidant Flavonols and Ischemic Heart Disease in a Welsh Population of Men: The Caerphilly Study. Am J Clin Nutr. May1997;65(5):1489-94.
2. Iso H, et al. The Relationship between Green Tea and Total Caffeine Intake and Risk for Self-Reported Type 2 Diabetes among Japanese Adults. Ann Inter Med. Apr 2006;144(8):554-562.