Thomas Jefferson University Hospital - Drinking Even Diet Soda May Be Harmful to Your Health

Drinking Even Diet Soda May Be Harmful to Your Health

Study shows link between soda - even diet varieties - and metabolic syndrome

Drinking more than one soft drink daily – even the sugar-free kind – may be associated with an increased incidence of metabolic syndrome, a study finds. Metabolic syndrome is a cluster of risk factors linked to the development of diabetes and cardiovascular disease.

The study’s senior author said the link to diet soda found in the study was striking but not entirely a surprise, as there had been some hints of it in earlier studies. The findings were published in July in Circulation: Journal of the American Heart Association and are the first to show the association in a prospective fashion and in a large population.

Barbara Berko, MD, cardiologist at Thomas Jefferson University Hospital, said the study is significant: “Soft-drink consumption has been related to obesity, and it is not surprising that it may also be associated with the development of the metabolic syndrome. Any factors that may contribute to this epidemic are important to recognize and address, in hopes of reversing this very unhealthy trend.”

Framingham study follow-up
The Framingham Heart Study has been following 6,000 participants since 1948. The heart study participants were free of any signs of metabolic syndrome when the study began. Metabolic syndrome includes the following signs:

High blood pressure
Elevated levels of triglycerides
Low levels of heart-protecting HDL cholesterol
High fasting blood sugar
Excessive waist circumference

Metabolic syndrome is the presence of three or more of these risk factors. Over the four years of the study, people who consumed more than one soft drink of any kind each day were 44 percent more likely to develop metabolic syndrome than those who did not drink a soda a day.

“That an association between soft drink consumption and metabolic syndrome exists is not surprising, particularly in view of the high sugar and calorie content of these drinks,” Dr. Berko says. “The fact that this association is the same for diet sodas as for regular sodas is somewhat less intuitive, however.”

Explanations unproven
The link between diet soft drink consumption and metabolic syndrome was clear even when the researchers accounted for other factors, such as levels of saturated fat and fiber in the diet, total calorie intake, smoking and physical activity. A variety of unproven explanations have been proposed for this association.

One theory is that the high sweetness of all soft drinks makes a person more prone to eat sugary, fattening foods. Another is that the caramel content of soft drinks promotes metabolic changes that lead to insulin resistance. Yet another is that soda consumption is a marker of dietary behavior – that is, that people who like to drink sweet soda also like to eat the kind of foods that cardiac nutritionists warn against.

“In this study, the group of people consuming the greatest amount of soda also had increased consumption of saturated and trans fats, lower dietary fiber consumption, an increased dietary glycemic index, and higher total caloric intake,” Dr. Berko notes.

However, the study authors warn that causality cannot be inferred. In other words, there is no proof that soda itself is the villain. Carefully controlled animal studies might resolve the cause-and-effect issue.

Study clarified after its release
Shortly after the study’s release, the American Heart Association (AHA) clarified the findings, stating this report “does not show that soft drinks cause risk factors for heart disease.” The statement also acknowledged that other factors could explain the development of risk factors for heart disease and that more research is needed.

Response from soft drink industry
The American Beverage Association states that it appreciates the heart group made clear “the report does… not show that soft drinks cause an increased risk of heart disease and it recognizes that diet soft drinks are a good option for those looking to cut calories in their beverages.”

Susan Neely, president of the American Beverage Association, adds, “The study does not establish any link between soft drinks, regular or diet, and increased risk of heart disease… diet soft drinks are terrific if you’re trying to watch weight and want something refreshing that tastes good and has no calories.”

Tips for women
Dr. Berko notes that the study showed a clear association between soda consumption and elevated triglyceride levels in particular.

“This will have a greater impact on the development of cardiovascular disease in women than in men, as do high sugar and carbohydrate foods in general,” she explains.

Another key factor for women: their influence over children’s dietary habits, including soda consumption.

“Learning and following good dietary habits from an early age is important, as the number of fat cells we have is determined in early childhood,” Dr. Berko says, adding that it’s much easier to maintain a healthy lifestyle as adults when such patterns of behavior are obtained in childhood rather than having to reverse bad habits at an older age.

“Women are in a unique position as mothers to help develop healthy eating habits in children, and therefore can have a major impact on the health of our society in general,” Dr. Berko says.

“Substituting water or juices for carbonated sodas as our primary beverages is key,” she concludes.

Always consult your physician for more information. Make an appointment with a Jefferson physician online or by calling 1-800-JEFF-NOW.