Coffee May Lower Diabetes Risk, but How?

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Acute effects of decaffeinated coffee and the major coffee components chlorogenic acid and trigonelline on glucose tolerance, by Aimée E. van Duk and colleagues. Diabetes Care 32:1023–1025, 2009

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

Drinking coffee has been linked to having a lower risk of getting type 2 diabetes. This link has been found with both caffeinated and decaffeinated coffee. This suggests that a component in coffee other than caffeine is the cause of this beneficial effect.

Why did the researchers do this particular study?

The researchers wanted to learn more about how components of coffee other than caffeine may affect the chances of getting type 2 diabetes.

Who was studied?

The study included 15 overweight but otherwise healthy nonsmoking men who were coffee drinkers.

How was the study done?

Researchers asked participants to drink no more than 1 cup of coffee per day for a week before each of 4 test days and to not drink coffee at all on the 4 test days. On each of the 4 test days, they gave participants one of the following: a serving of decaffeinated coffee, a serving each of two individual components of coffee (chlorogenic acid and trigonelline) dissolved in water, or a placebo (dummy) serving. They then gave participants a 2-hour oral glucose tolerance test (a test used to diagnose diabetes that involves drinking glucose and measuring how the body processes it) and measured their blood glucose and insulin levels.

What did the researchers find?

Both the chlorogenic acid and trigonelline solutions lowered glucose and insulin levels 15 minutes after the start of the glucose tolerance test compared with the dummy solution. Decaffeinated coffee, which contained less of each substance than the separate solutions, did not lower glucose and insulin levels. None of the substances affected overall insulin or glucose levels during the full length of the glucose tolerance test.

What were the limitations of the study?

Because the study involved multiple tests conducted at different time points, its findings may have been due to chance. Also, because the decaffeinated coffee had smaller levels of chlorogenic acid and trigonelline than the individual solutions of those substances, the effects of each were hard to compare.

What are the implications of the study?

Coffee's link to a lower risk for type 2 diabetes appears to be related to coffee components other than caffeine. This study suggests that two components—chlorogenic acid and trigonelline—play a role, but more study is needed to fully understand what this means for people who drink coffee.

FOR MORE INFORMATION

Coffee and Diabetes

Diabetes Prevention

The Disease Prevention Cookbook