Ask The Expert
Eating Well

First. If you haven’t already done so, please review my other answer from the educator archives, about caffeine and diabetes.

In that answer, I explained that while some articles suggested that large amounts of coffee (over 500 mg caffeine) could raise blood glucose, the general consensus was that moderate coffee drinking would not affect blood glucose levels, because supposedly the average daily caffeine consumption is approximately 200 mg. But obviously it would depend on the amount of caffeine you consume in a day.

On January 5, 2004 several news reports commented on an article featured in the January issue of Annals of Internal Medicine titled: “Coffee Consumption and Risk for Type 2 Diabetes Mellitus”.

What Was Known:

A previous study in the Netherlands showed that people who drank at least 7 cups of coffee a day were half as likely to develop type 2 diabetes as people who drank 2 cups or less a day; however, that study did not differentiate between caffeinated and decaffeinated coffee and did not ask the subjects about other caffeine-containing drinks.

Details of this Study:

• Researchers sought to study the relationship between type 2 diabetes and any type of coffee, as well as caffeine-containing drinks.
• Researchers examined surveys from 41,934 men from a U.S. Health Professionals Follow-up Study, as well as 84,276 women from the Nurses' Health Study. None of the participants had diabetes, cancer, or heart disease at the start of this survey.
• Participants completed questionnaires every 2-4 years, which included questions about the frequency of coffee and other beverage ingestion.
• Researchers then compared the frequency of developing type 2 diabetes with the different intakes of coffee.

Results:

• The study found that people who drank more coffee were less likely to develop type 2 diabetes, and the relationship was stronger in women than in men. The survey found no relationship between decaffeinated coffee intake and type 2 diabetes.

Cautions/Limitations:

Because this was simply a survey, the study did not enable researchers to be sure that coffee decreases the incidence of type 2 diabetes. It could be something else about coffee drinkers that protects them from diabetes.

Please note that you asked if coffee is good for diabetes—and this study does not report anything beneficial about caffeine and pre-existing diabetes, but rather it suggests a possible reduction in the risk of getting diabetes.

Furthermore, in the American Diabetes Association (ADA) e-news bulletin of 1/6/2004, Dr. Nathaniel Clark expressed concerns that this report would divert public attention toward “illusory quick-fixes and away from proven diabetes-stoppers: diet, weight loss and exercise.”

Conclusion:

The authors concluded that further research should examine the influence of caffeine on sugar metabolism.

So while the news headlines sound exciting, it is important to understand the limitations of the study. It is premature to make any official conclusions. As always, be sure to discuss this with your diabetes team.