Diet soft drinks are lower in calories, but are still associated with a greater risk of heart disease as are sugar-laden sodas, according to a new study. US researchers tracked for four years the health of more than 6,000 middle-aged adults and found those who drank one or more soft drinks daily had an increased risk for metabolic syndrome when compared to individuals who drank fewer of the fizzy beverages.
Metabolic syndrome is a cluster of risk factors for heart disease and diabetes such as high blood pressure, excessive fat around the waist and low levels of “good” cholesterol.
What surprised researchers was that diet drinkers were no better off than drinkers of sugary sodas.
“We were struck by the fact that it didn’t matter whether it was a diet or a regular soda that participants consumed,” said Boston University School of Medicine professor Ramachandran Vasan.
By the end of four years, the consumers of soft drinks had a 31 percent greater risk of becoming obese, a 30 percent greater risk of increased weight circumference and a 32 percent greater risk of having low levels of HDL or, so-called good cholesterol. They also had a 25 percent higher risk of having high blood triglycerides or high blood glucose.
About half of the participants kept detailed food questionnaires which showed which sodas they drank, regular or diet. Researchers were surprised to find that the sugar content of the drinks made no difference to the health outcomes.
Adults who drank one or more sodas a day had a 50 to 60 percent greater chance of having developed metabolic syndrome – despite drinking diet or regular sodas.
Researchers say it is not clear why diet sodas raise a person’s risk for metabolic syndrome. “It may be that soft drinks condition a person’s palate, making them more likely to eat sweet, calorie-rich foods,” said Ravi Dhingra, lead author of the paper and an instructor in medicine at Harvard Medical School.
Alternatively, some experimental studies show that the caramel content in soft drinks may promote development of complex sugars that can result in insulin resistance and diabetes.
“These are all theories and experts debate their importance,” said Dhingra. “Our study was observational and so right now all we demonstrate is an association. We have not proven causality.” – AFP/de
This study is observational and does not show cause and effect. The study authors note in the paper, “Individuals with greater intake of soft drinks also have a dietary pattern characterized by greater intake of calories and saturated and trans fats, lower consumption of fiber and dairy products and a sedentary life.” Experts agree that factors such as caloric imbalance and sedentary lifestyle are related to weight gain, heart disease and metabolic syndrome. Further the researchers note, “Given the observational nature of the present study, we cannot infer that the observed associations are causal. As noted above, it is conceivable that residual confounding by lifestyle/dietary factors not adjusted for may have contributed to the metabolic risks associated with soft drink intake.”
Leading health groups agree that low-calorie sweeteners and the products that contain them can help people manage their weight as part of an overall healthy diet. Even the American Heart Association recommends, “Substitute lower-calorie foods for high-calorie foods. You can subtract calories by making small but effective changes in your daily eating patterns.” Further, according to the American Dietetic Association, “Non-nutritive sweeteners added to the diet have been shown to promote modest loss of weight and, within a multi-disciplinary weight-control program, may facilitate long term maintenance or reduction in body weight.” No major health group is making a change to its dietary recommendations based on this observational study.
The American Heart Association, in its July 23, 2007 press release on the study, states: “Since this is an observational study, it is important to note that the study does not show that soft drinks cause risk factors for heart disease.” AHA adds: “Diet soda can be a good option to replace caloric beverages that do not contain important vitamins and minerals. The American Heart Association supports dietary patterns that include low-calorie beverages like water, diet soft drinks, and fat-free or low-fat milk as better choices than full calorie soft drinks.”
the journal Circulation, July 2007