NEW YORK (Reuters Health) - It might be better to start your morning with a cup of coffee than a sugar-sweetened juice, at least where risk for type 2 diabetes is concerned, a new study suggests.

Researchers found that among more than 12,000 middle-aged adults, those who drank four or more cups of coffee each day had a lower risk of developing type 2 diabetes than those who rarely had a cup.

The findings, reported in the American Journal of Epidemiology, agree with those of several past studies.

The reason is not fully clear, but one possibility is that certain coffee components -- such as magnesium or chlorogenic acid -- improve the body's regulation of blood sugar. Some research also suggests that caffeinated coffee spurs a prolonged spike in metabolism that may help control body weight.

Type 2 diabetes arises when the body loses sensitivity to the hormone insulin, which shuttles sugar from the blood into cells to be used for energy. The disorder is closely associated with obesity.

In contrast to the case with coffee, sugar-filled soft drinks and juices have been linked to obesity and higher diabetes risk in certain studies.

In the current one, however, a taste for sweet drinks was not a risk factor for diabetes.

Still, the findings are not a green light to fill up on coffee and sugary drinks, according to the researchers, led by Nina P. Paynter, a doctoral candidate at the Johns Hopkins School of Public Health in Baltimore.

Moderation, as always, is in order, the study's senior author, Dr. W. H. Linda Kao, told Reuters Health.

"We feel it is definitely premature to recommend coffee consumption," she advised. While there's no evidence coffee is "bad" as far as diabetes risk, research has linked it to other conditions, such as elevated blood pressure, Kao pointed out.

As for the lack of a connection between sugary drinks and type 2 diabetes, the researchers say it's something of a surprise. In general, though, the middle-aged adults in their study drank few sugar-laden beverages, so it's possible this obscured any relationship to diabetes, according to Kao and Paynter.

"Moderation with coffee is still important and sweetened beverages should still be approached with caution," Kao said.

The Hopkins researchers based their findings on data from 12,204 middle-aged U.S. adults who were followed from 1987 to 1999 -- all of who were free of diabetes at the outset.

Participants completed detailed questionnaires on their diets, including how often they drank coffee and sugar-sweetened soft drinks and juices. They also reported on their exercise levels, smoking habits, alcohol intake and other lifestyle factors.

Even with these other factors considered, coffee drinkers showed a lower risk of developing type 2 diabetes. Those who downed four or more cups each day were about one-third less likely to report a diabetes diagnosis over the study period.

But while the coffee-diabetes connection is "intriguing," Kao said, more research is needed to determine whether the beverage itself has a true effect on diabetes risk.