Drinking Coffee Can Help Lower the Risk for Type 2 Diabetes in Women

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Coffee, caffeine, and risk of type 2 diabetes: a prospective cohort study in younger and middle-aged U.S. women, by R.M. van Dam and colleagues. Diabetes Care 29:398–403, 2006.

What is the problem and what is known about it so far?

Previous studies have shown that people who drink a lot of coffee have a lower risk for type 2 diabetes. However, researchers don't know what ingredient in coffee lowers the risk for type 2 diabetes. Is it because some types of coffee contain caffeine? Or is it because coffee contains other things, like certain ingredients that are antioxidants (substances that protect against cell damage)? In addition, there aren't many studies that have looked at whether drinking small amounts of coffee is also linked with a lower risk for type 2 diabetes.

Why did the researchers do this particular study?

To see if drinking small amounts of coffee lowers the risk for type 2 diabetes, and to see how different types of coffee (such as caffeinated versus decaffeinated coffee) affect the risk for type 2 diabetes.

Who was studied?

About 88,000 women who took part in the Nurses' Health Study II. The women were between 26 and 46 years old, and none had diabetes when the study began.

How was the study done?

The researchers looked at data from the Nurses' Health Study II, which began in 1989. The women who took part in the study were sent questionnaires every two years; the questionnaires asked about the women's health and their lifestyle, including what they ate and drank on the average day. The researchers looked at the responses from questionnaires sent in 1991, 1995, and 1999. They then compared the rate of diabetes among women who drank no coffee per day, women who drank one cup of coffee each day, women who drank two or three cups each day, and women who drank four or more cups each day.

What did the researchers find?

The women who drank two or more cups of coffee each day had a much lower risk for type 2 diabetes than the women who drank no coffee or only one cup of coffee each day. It didn't matter whether the coffee was caffeinated or decaffeinated.

What were the limitations of the study?

This study wasn't able to account for cup size of strength of coffee. Also, the researchers weren't able to screen the women's blood glucose levels, so some cases of type 2 diabetes may have gone undiagnosed.

What are the implications of the study?

Drinking moderate amounts of coffee (two to four cups each day), whether caffeinated or decaffeinated, may lower the risk for type 2 diabetes in younger and middle-aged women.

If you have diabetes, please keep in mind that caffeine can dehydrate you. If you drink a lot of caffeinated coffee, make sure you drink plenty of water.

FOR MORE INFORMATION

Essential Water: Make Sure You Get Enough

Drinking More Coffee May Lower Risk of Type 2 Diabetes

Caffeine, Exercise, and Glucose