Also see: "Coca-Cola & the Nazis":
By Stephanie Desmon
July 24, 2007
Vasan had expected a link between heart health risk and sugar-sweetened, high-calorie drinks. But the diet soda findings puzzled him. So the researchers called for more study when they published their findings yesterday in Circulation, the peer-reviewed journal of the American Heart Association.
Although the study merely suggested that diet soda might be less than innocuous, the beverage industry and a friendly think tank attacked the work even before the results were made public - concerned that consumers might find yet another reason to drink water instead.
For the record, Vasan agrees. "I'm a scientist. My job is to let the data speak for itself," said Vasan, a cardiologist, professor at the Boston University School of Medicine and the paper's senior author.
The researchers used data collected as part of the respected Framingham Heart Study, which has followed the health of thousands of people for decades.
The latest study showed that as little as one 12-ounce soda a day increases the risk of developing so-called "metabolic syndrome," a cluster of conditions that increase risk for heart disease as well as diabetes and stroke.
To qualify, a patient must have three of these five risk factors: abdominal obesity (excessive fat in and around the abdomen), low levels of so-called "good cholesterol," high blood pressure, insulin resistance and high triglycerides.
The study was not a clinical trial, designed to prove or disprove a hypothesis, but one that observed participants' health and lifestyle over several years.
The data were consistent enough for researchers to find an association between soda and heart risk factors - but not a cause and effect, Vasan said. The link was evident even when the researchers accounted for other factors, such as age, levels of saturated fat in the diet, total calories consumed, smoking and physical activity.
"It's a puzzling finding that I can't explain," said Dr. Kelly Brownell, professor of epidemiology and public health director of the Rudd Center for Food Policy and Obesity at Yale University, who was not involved in the study, "but a very important one to follow."
Researchers did posit some theories, however. One is that the sugary flavor of all soft drinks - with or without calories - makes a person more prone to eat sugary, fattening foods. Another is that the caramel color in many soft drinks promotes metabolic changes that lead to insulin resistance.
Vasan said it might be that drinking soda - even diet varieties - is a "marker" for other dietary behaviors, meaning people who drink sweet-tasting soda are also people who make unhealthy food choices. For example, they might drink a Diet Coke with a Big Mac and fries to lessen calorie consumption.
Vasan said he hopes this work inspires additional studies of diet soda and its link to heart health.
No one contends that soft drinks are healthy. Sugary soda has already been linked to weight gain and obesity in children, to a decrease in bone density in women, to diabetes and to the wearing-away of tooth enamel. Diet soda has also been associated with weight gain and hypertension - although not as a direct cause of either.
Susan Neely, president and CEO of the American Beverage Association, said she wants to make sure people get the message that they should "eat and drink in moderation."
In an interview later, Neely said her group's goal is to make sure no one is "confused" about the study's conclusions. "We're bombarded with a lot of health information as consumers, and it's hard to sort out," she said.
Liquid calories have increased from 12 percent or less of calories we consume to 25 percent in the past decade, said Dr. Benjamin Caballero, a pediatrician and nutrition professor at the Johns Hopkins Bloomberg School of Public Health.
He said he wants to see further studies into carbonated beverages but concluded that this study alone is "not enough to make a broad policy change."
The medical community and various food and beverage interests have long squared off over studies such as this one, which frequently put the industry on the defensive.
Both have watched as politicians have used public awareness of medical research in attempts to legislate healthier behaviors.
New York City has famously banned trans-fats in its restaurants, forcing fast-food giants to change their long-time recipes. Many cities have banned smoking in all workplaces - including bars and restaurants.
Soft-drink manufacturers have attempted pre-emptive strikes against the argument that they peddle empty calories. Many have taken their products out of school vending machines, sometimes by their own choice, other times by dictate.