Can Coffee Worsen Diabetes?

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Q: I am a 35-year-old man with Type 2 diabetes. My doctor is concerned that my coffee intake may be harmful for my condition. Should I be concerned?

A: The concern brewing over your coffee is related to its caffeine content rather than the coffee itself. That’s because several small studies have linked caffeine intake to a rise in blood sugar levels in those who were already affected with Type 2 diabetes. This was especially noticeable in the immediate hours after consuming a meal.

So what does this mean for you? If your blood glucose levels are poorly controlled in spite of smart dietary choices, regular exercise and oral diabetic medications, it may prove helpful to switch to decaffeinated coffee as well as to limit your intake of caffeine containing food and drink products.

The detriments of coffee

The concern about how caffeine effects those with Type 2 diabetes revolves around several small studies. Most recently, Duke University studied 10 people (average age 63) wearing a continuous blood glucose monitor for 72 hours. All were regular coffee drinkers (four cups per day) and all were affected with Type 2 diabetes.

During the study the participants did not drink coffee and instead were given a 250 milligram capsule of caffeine (similar to drinking two to three cups of caffeinated coffee) at breakfast and another 250 milligram capsule of caffeine at lunch. This was alternated on an every other day basis with a placebo pill that did not contain caffeine for a period of two days.

The result: Participants averaged an eight percent increase in blood sugar levels on the days they took the caffeine capsules as well as a nine to 26 percent increase in their blood sugar levels after meals. However, it is important to note that the study was small and involved caffeine capsules instead of brewed coffee. Even so, the results were concerning, thus more studies on the relationship between caffeine and Type 2 diabetes are underway.

Other small studies seem to indicate that the caffeine in coffee may elevate blood sugar levels in those who are already affected by Type 2 diabetes.

Are there benefits to coffee?

While the Duke study suggests that caffeinated coffee may be a bad habit for diabetics, other studies have shown a decreased risk for developing Type 2 diabetes in those who drink two or more cups per day. To understand why there are puzzling contradictions in these outcomes, remember that coffee is not caffeine alone.

While the caffeine may potentially impede the movement of blood glucose into blood cells in those with Type 2 diabetes, there are other ingredients in coffee (not the cream and sugar) that may prove beneficial as our bodies attempt to control blood sugar:

Magnesium – may help the body use carbohydrates more efficiently and decrease the risk for type 2 Diabetes
Chlorogenic acid – a polyphenol (type of antioxidant) that may decrease blood glucose levels
Quinides – may improve insulin sensitivity and improve blood glucose control

As shown in this study, there may grounds to support the benefits of a cup or two of coffee (decaf) per day.

Fortunately, Type 2 diabetes can often be managed through a combination of regular exercise, a healthy diet and weight control, as well as different categories of medications if further blood glucose control is needed.

For further information and advice on managing your Type 2 diabetes, speak with your physician and visit the American Diabetes Association, Global Diabetes Community, or the Defeat Diabetes Foundation.

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Robert Danoff, D.O., M.S., is a family physician and program director of The Family Practice Residency, as well as the combined Family Practice/Emergency Medicine Residency programs at Frankford Hospitals, Jefferson Health System, Philadelphia, Pa. He is the medical correspondent for CN8, The Comcast Network, a regular contributor to Discovery Health Online and a contributing writer to The New York Times Special Features. (Read his full bio.)