Women in the study who drank at least one sugar-sweetened soda a day were 85 percent more likely to develop type 2 diabetes than those who drank less, said Matthias B. Schulze, who presented the Harvard School of Public Health research at the American Diabetes Association's 64th scientific sessions.
In addition to the sodas' excess calories, their large amount of rapidly absorbable sugars could contribute to obesity and a greater risk of diabetes, said Schulze, a post-doctorate student from Germany.
"It's not that sugar everywhere is important, but it seems that sugar specifically in liquid foods may be relevant," Schulze said. "So, sodas and other energy-providing drinks may lead to an over-consumption of energy that would lead to obesity and weight gain."
Diet sodas with sugar substitutes, however, did not increase the chances of developing diabetes, Schulze said. He added that the women who drank diet sodas tended to lose weight.
Diabetes is an illness that develops, often in middle age, when a body loses the ability to turn blood sugar into energy. There were 18.2 million Americans — 6.3 percent of the population — with diabetes in 2002, and it is the nation's fifth-deadliest disease, says the American Diabetes Association.
Worse yet, diabetes is a growing problem. The prevalence of diabetes was fairly flat during the 1980s, but nearly doubled from 1990 to 2002.
According to Schulze's study, the women most prone to gaining weight had increased their consumption of sugary soft drinks from less than one a week to more than one a day. On average, those women gained 9-10 pounds in a four-year period. But women who cut their intake of soft drinks gained an average of 3 pounds or less.
The research followed more than 91,000 adult women over an eight-year period. It is part of the Nurses Health Study at Boston's Brigham and Women's Hospital.
The research comes two months after the release of a British study showing school programs that discouraged drinking sodas appeared to be effective in reducing obesity among children.
Mike Jacobsen, executive director for the Center for Science in the Public Interest consumer advocacy group, said he wasn't surprised by the study's findings — but he was pleased.
"It provides ammunition for education efforts, labeling changes and restricting soft drink consumption in schools," Jacobsen said.
The National Soft Drink Association labeled the study as "unconvincing and inconclusive," because it has yet to be peer-reviewed and raises questions over factors that could create inaccuracies.
Schulze acknowledged the study's limitations in that its data came from observations, such as body weight the women themselves reported.
By Mike Branom
By Mike Branom