Health authorities report that drinking as little as one can of soda a day is associated with a 48 percent increased risk of metabolic syndrome, a key predecessor of heart disease and diabetes.
The results were published online in Circulation: Journal of the American Heart Association.
The team focused on the more than 1,000 people who did not have metabolic syndrome at the start of the study and followed them for at least four years.
The study found that those who drank at least one soda a day had a 44 percent higher risk of developing metabolic syndrome during the four years of the study.
The finding found that the percentages were the same whether subjects drank regular or diet soda.
Researchers were uncertain why diet soda seemed to have such a large effect.
Dr. Ramachandran S. Vasan of the Boston University School of Medicine said it was unlikely that an ingredient in soda caused the effect. He said that the risk is associated with consuming sweet sodas which change dietary patterns.
In the study, sponsored by the National Heart, Lung and Blood Institute, Vasan and his colleagues studied more than 2,400 middle-age white residents of Framingham, Mass.
At the beginning of the study, those who had consumed more than one soda per day--either regular or diet--had a 48 percent higher risk of having metabolic syndrome.
Those who drank at least one soda a day had a 31 percent greater risk of becoming obese; a 30 percent higher risk of having a larger waistline; a 25 percent higher risk of developing high blood triglycerides or high blood sugar an 32 percent grater risk of having low levels of good cholesterol; a trend toward an increased risk of high blood pressure.
The percentages were the same whether subjects drank regular or diet soda.
Vasan said that research also indicated that people who drank sodas also tended to have diets higher in calories, saturated fats and trans fats and lower in fiber and that they were also more sedentary.
One theory is that drinking sweet sodas may get people used to a sweet taste and into the snacking mode, said Dr. Meir Stampfer. Its not the artificial sweetener, but what goes along with it.
Dr. Stampfer said he was not surprised by the association. The doctor said that he had previously reported that diet sodas increase the risk of obesity and high blood pressure.
Soda makers rejected the study. Susan K. Neely, president of the chief executive of the American Beverage Association, said, It is scientifically implausible to suggest that diet soft drinks--a beverage that is 99 percent water--can cause weight gain or elevated blood pressure.
Metabolic syndrome is a cluster of symptoms including excessive abdominal fat, high blood-glucose levels, high blood pressure, high blood triglycerides and low levels of high-density lipoprotein, the so-called cholesterol.
People who have three or more of these symptoms have double the normal risk of heart disease and diabetes.