BOSTON (AP) — People who drank more than one diet soda each day developed the same risks for heart disease as those who downed sugary regular soda, suggests a large but inconclusive study.
The results surprised the researchers who expected to see a difference between drinkers of regular and diet soda. It could be, they suggest, that even no-calorie sweet drinks increase the craving for more sweets and that people who indulge in sodas probably have less healthy diets overall.
The study's senior author, Dr. Vasan Ramachandran, emphasized that the findings don't show that diet sodas are a cause of increased heart disease risks. But he said they show a surprising link that must be studied.
"It's intriguing, and it begs an explanation by people who are qualified to do studies to understand this better," said Dr. Vasan of Boston University.
However, a nutrition expert dismissed the study's findings on diet soda drinkers.
"There's too much contradictory evidence that shows that diet beverages are healthier for you in terms of losing weight that I would not put any credence to the result on the diet" drinks, said Barry Popkin, of the University of North Carolina in Chapel Hill, who has called for cigarette-style surgeon general warnings about the negative health effects of soda.
Susan Feely, president of the American Beverage Association, said the notion that diet drinks are associated with bulging waistlines defies common sense.
"How can something with zero calories, that's 99 percent water with a little flavoring in it ... cause weight gain?" she said.
The research comes from a massive, multigenerational heart study of residents of Framingham, Mass., a town about 25 miles west of Boston. The new study of 9,000 observations of middle-aged men and women was published yesterday online in the journal Circulation.
The researchers found that those who drank more than one soda per day — diet or regular — had an increased risk of metabolic syndrome, compared with those who drank less than one soda. Metabolic syndrome is a cluster of symptoms that increase the risk for heart disease, including large waistlines and higher levels of blood pressure, blood sugar, cholesterol and blood fats called triglycerides.
At the start of the study, those who reported drinking more than one soft drink a day had a 48 percent increased prevalence of metabolic syndrome compared with those who drank less soda.
Of participants who initially showed no signs of metabolic syndrome, those who drank more than one soda per day were at 44 percent higher risk of developing it four years later, they reported.
Researchers had expected the results to differ when drinkers of regular soda and diet soda were compared and were surprised when they did not, Dr. Vasan said.
But Mr. Popkin said that result isn't that surprising. He said much of the market for diet sodas are people who have unhealthy lifestyles and know they need to lose weight — with the other portion being thin people who want to stay that way. That means many people drinking diet sodas have unhealthy habits that could lead to increased heart disease risks, whether they drink diet soda or not.