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Diabetes Perk From Decaf Coffee?

Drinkers of Decaf Coffee Show Lowest Risk in 11-Year Study
WebMD Health News
Reviewed by Louise Chang, MD

June 26, 2006 -- Postmenopausal women who drink at least six daily cups of coffee -- especially decaffeinated coffee -- may be less likely to develop type 2 diabetes than those who never drink coffee.

So says a study in the Archives of Internal Medicine. Researchers from the University of Minnesota's School of Public Health -- including Mark Pereira, PhD -- studied more than 28,800 Iowa women for 11 years.

When the study started in 1986, none of the women had diabetes. They completed questionnaires on diet, exercise, height, weight, smoking, alcohol use, and waist-to-hip ratio.

Almost half of the group -- more than 14,200 women -- reported drinking one to three daily cups of coffee. About 2,900 others reported no coffee consumption, and more than 2,800 noted six or more daily cups of coffee.

The women were more likely to drink regular (caffeinated) coffee than decaf coffee, especially if they drank a lot of coffee, the researchers note.

Diabetes Rarer in Coffee Drinkers

When the study ended in 1997, about 1,400 women had been diagnosed with type 2 diabetes.

The chances of developing type 2 diabetes increase with age. The researchers took that into account, along with other factors that could raise or lower the risk of developing diabetes.

"Compared with women who reported 0 cups of coffee per day, women who consumed 6 or more cups per day had a 22% lower risk of diabetes," write Pereira and colleagues. "This association appeared to be largely explained by decaffeinated coffee."

The study was observational, meaning that the researchers didn't ask the women to change their coffee-drinking habits. So the results don't prove that coffee wards off type 2 diabetes.

Secret Ingredient?

Pereira's team doesn't know how to explain the study's results. The data -- which included adding cream, milk, or sugar to coffee -- showed no solid clues.

Caffeine and magnesium, a mineral found in coffee, didn't explain the results. Other chemicals in coffee that haven't been studied yet may cut diabetes risk, note Pereira and colleagues.

Should postmenopausal women sip coffee to help prevent diabetes? Pereira's study stops short of making any promises.

"Although the first line for prevention of diabetes is exercise and diet, in light of the popularity of coffee consumption and high rates of type 2 diabetes mellitus in older adults, these findings may carry high public health significance," they write.

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