Diet soda tied to illness

Researchers link it to heart disease

Drinking as little as one can of soda a day -- either regular or diet -- is associated with a 48 percent increased risk of "metabolic syndrome," a predecessor of heart disease and diabetes, according to results released Monday.

Researchers previously knew that drinking regular sodas contributed to the risk of metabolic syndrome, but this is the first finding implicating diet sodas, according to results published online in Circulation: Journal of the American Heart Association.

The researchers don't know why diet soda had such a large effect.

But Dr. Ramachandran S. Vasan of Boston University School of Medicine, the lead author of the study, said it is unlikely that an ingredient in diet soda causes the effect. More likely is that consuming sweet sodas changes dietary patterns or that soda is simply a marker for poor eating habits.

Dr. Meir Stampfer of Harvard Medical School, who was not involved in the study, said the findings were not unexpected, although he added, "I'm surprised by the magnitude of the association."

Stampfer previously reported that diet sodas increase the risk of obesity and high blood pressure.

Soda makers, however, rejected the study outright.

Susan K. Neely, president and chief executive of the American Beverage Association, said that "the assertions defy the existing body of scientific evidence, as well as common sense ... It is scientifically implausible to suggest that diet soft drinks -- a beverage that is 99 percent water -- cause weight gain or elevated blood pressure."

Metabolic syndrome is a cluster of symptoms that includes excessive abdominal fat, high blood-glucose levels, high blood pressure, high blood triglycerides and low levels of high-density lipoprotein, the "good" cholesterol.

People with three or more of these symptoms have double the normal risk of heart disease and diabetes.

Vasan said research has shown that people who drink sodas also tend to have a diet that is higher in calories, higher in saturated fats and trans-fats and lower in fiber. They also are more sedentary.

The authors tried to control for all those factors in the diet, but "even after all that, we still found an increased risk," he said. "Maybe it is very difficult to adjust for lifestyle."

Another possibility is that drinking soda with a meal reduces the feeling of satiety, so that the person eats more at the next meal, he said.

Alternatively, drinking sweet sodas might get people used to a sweet taste and "into the snacking mode," Stampfer said. "It's not the artificial sweetener, but what goes along with it."

None of those theories, however, has been confirmed by experiments.

"Our task is to report associations," Vasan said. "We do not claim that this is a causal link. It is up to scientists to help us understand this better."