Sodas Linked Again to Heart Disease

Is drinking soda, whether diet or regular, a strong link to heart disease? Researchers at the Framingham Heart Study of the Boston University School of Medicine think there's such a strong association that they are calling for further study, according to an article published in the recent online edition of Circulation: Journal of the American Heart Association.

Although this is not the first study to link soda consumption to heart disease risks, the current study revealed that both diet and regular sodas provide risks. Even adjusting for saturated fat and trans fat intake, dietary fiber consumption, total caloric intake, smoking, and physical activity, the researchers still observed a significant association of soft drink consumption with the risk of developing the metabolic syndrome and multiple metabolic risk factors.

Metabolic syndromes -- a cluster of heart and diabetes risk factors -- are large waist circumference, high blood pressure, elevated triglycerides, low levels of high-density lipoprotein (HDL "good" cholesterol), and high fasting glucose levels. The presence of three or more of the factors increases a person's risk of developing diabetes and cardiovascular disease.

The Framingham study included nearly 9,000 middle aged men and women observed at three different times over a four-year period. Those who consumed one or more soft drinks daily had a 48% increase of metabolic syndrome compared with those who drank less than one soft drink daily. Study participants who had no metabolic syndrome (6,039 people) who consumed one or more soft drinks daily had a 44% higher risk of developing new onset metabolic syndrome.

Compared to participants who drank less than one soft drink daily, those participants who drank one or more soft drinks per day had a 31% greater risk of developing new onset obesity, a 30% increased risk of developing increased waist circumference, and a 25% increased risk of developing high blood triglycerides or high fasting blood glucose. Other results were a 32% increase in risk of low HDL levels and a trend toward developing high blood pressure, although researchers said this particular risk was not statistically significant.

So why do both diet and regular sodas show some risk? At the moment, there are many theories and no conclusive evidence, but some factors may be the fructose corn syrup in regular soft drinks causes weight gain and can lead to insulin resistance and diabetes. The high levels of sweetness in both diet and regular soft drink can lead people to eat more sweets. The caramel content in soft drinks may promote development of advanced glycation end products, complexes of sugars, which can result in insulin resistance.

Poor overall health habits may be one reason diet soda drinkers did not show lower heart disease risks in the Framingham study. Lastly, it could be "dietary compensation," in which a person who drinks a large amount of liquids at a meal is not satisfied and then eats more at the next meal.

Although the study raises many theories, it did demonstrate an association between drinking soda and increased risks of heart disease. Now, the objective of researchers is to understand the mechanisms driving this association before recommendations can be made.