MONDAY, June 26 (HealthDay News) -- Drinking lots of coffee cut women's risk of developing diabetes in an 11-year study, researchers report. But it was the antioxidants, not caffeine, in the brew that probably did the trick.
In fact, diabetes risk was reduced most in participants who preferred decaffeinated coffee, the researchers said.
"In our study, for whatever reason, it doesn't look like caffeine has anything to do with it," said lead researcher Mark A. Pereira, an associate professor of epidemiology and community health at the University of Minnesota, Minneapolis.
His team published its findings Monday in the Annals of Internal Medicine.
In the study, Pereira's team gathered data on nearly 29,000 older women who answered questions about risk factors for diabetes such as age, body mass index, physical activity and smoking. They also reported on their consumption of various foods and beverages, including regular and decaffeinated coffee.
Adjusting for those risk factors, the researchers found that women who drank more than six cups a day of any type of coffee were 22 percent less likely to develop type 2 diabetes, the kind that occurs in adult life, compared to those who avoided coffee.
But diabetes risk dropped even more -- by 33 percent -- for those who drank more than six cups a day of decaf, the study authors found.
Pereira pointed out that coffee has many components, including powerful antioxidant chemicals similar to those found in berries and grapes.
"When you get up to four or five or more cups per day, you might have very powerful antioxidant activity," he said. "That might be important for protecting the pancreas' beta cells from oxidant damage," he said.
Beta cells produce insulin. Adult, or type 2, diabetes, occurs as the body slowly loses its ability to produce insulin.
The report was described as "not surprising" by Rob van Dam, a research scientist at the Harvard School of Public Health. He was part of a research team in the Netherlands who first reported the protective effect of coffee in 2002. Several other studies, including one done at the Harvard School of Public Health, have backed up those original findings.
"We found exactly the same protective effect of decaffeinated coffee," van Dam said. "People think that if coffee causes it, it must be the caffeine, but coffee is a very complex mixture," he added.
One component of coffee that has caught van Dam's attention is chlorogenic acid, which seems to be able to slow the absorption of sugar by cells. Studies in rats found that the molecule lowered blood-sugar levels, he said.
There's another reason to hope that chlorogenic acid is beneficial: According to van Dam, it's abundant in both red wine and chocolate. "People think that nutritionists are always recommending things they don't like, but that's not true," he said.
Still, he and Pereira agreed that it's much too early to single out any one component of coffee as beneficial.
"Clearly, the next step is experimental studies in humans," van Dam said.
"It's going to take some really meticulous clinical trials," Pereira added.
The study was funded by a grant from the U.S. National Cancer Institute.
Meanwhile, in a joint statement released today, The American Diabetes Association and American Heart Association called Monday for greater prevention and treatment efforts to stem the continuous rise in diabetes and in cardiovascular-related deaths that related to under-treated risk factors.
"The importance of identifying a core set of risk factors such as pre-diabetes and diabetes, prehypertension and hypertension, dyslipidemia and obesity cannot be overstated," said Dr. Robert H. Eckel, president of the AHA. "It is long past time to start getting these risk factors under control through lifestyle changes and medication. It's not as if we don't know how. The research is there," he said.