Here’s another reason to add coffee to your cart when you visit your local natural or organic food store: Drinking coffee—especially decaf—may be associated with a reduced risk of type 2 diabetes, according to a report in the June 26 issue of Archives of Internal Medicine.

Previous U.S. and European studies have linked coffee to a reduced risk of type 2 diabetes. In fact, most research has found that the more coffee you drink, the lower your risk for diabetes. But it remains unclear whether it’s the caffeine or another ingredient that offers protection.

Mark A. Pereira, PhD, and his colleagues at the University of Minnesota, Minneapolis, studied coffee intake and diabetes risk in 28,812 postmenopausal women over an 11-year period. At the beginning of the study (1986), the women answered questions about their risk factors for diabetes, including age, body mass index, physical activity, alcohol consumption and smoking history. They also reported how often they consumed a variety of foods and beverages over the previous year, including regular and decaffeinated coffee.

Based on information reported in the initial questionnaire, about half of the women (14,224) drank one to three cups of coffee per day; 2,875 drank more than six cups; 5,554 four to five cups; 3,231 less than one cup; and 2,928 none. Over the following 11 years, 1,418 of the women reported they had been newly diagnosed with type 2 diabetes. After researchers adjusted the data for other diabetes risk factors, they found women who drank more than six cups of any type of coffee per day were 22% less likely than those who drank no coffee to be diagnosed with diabetes. Those who drank more than six cups of decaffeinated coffee per day had a 33% reduction in risk compared with those who drank none.

Overall caffeine intake did not appear to be related to diabetes risk, further suggesting that some other ingredient in coffee was responsible.

“Magnesium, for which coffee is a good source, could explain some of the inverse association between coffee intake and risk of type 2 diabetes mellitus through known beneficial effects on carbohydrate metabolism,” the authors write. But the study found no association between this mineral and diabetes risk. Other minerals and nutrients found in the coffee bean—including compounds called “polyphenols” that help the body process carbohydrates and antioxidants—may contribute to its beneficial effects and should be examined in future studies.

“Although the first line of prevention for 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,” the authors conclude.