Not So Sweet News About Soda

It’s no secret that drinking soda, which is loaded with sugar and empty calories, can pack on the pounds, but a new study conducted by BU doctors reveals more dire results — drinking even one can of soda a day, regular or diet, can increase your risk factors for heart disease. The study was conducted by doctors at the Framingham Heart Study, the long-running National Heart, Lung, and Blood Institute epidemiological study begun in 1948 and run by BU since 1971, and the results were published in the July 31 issue of Circulation, the journal of the American Heart Association.

“We were struck by the fact that whether it was diet or regular soda that participants consumed, the association with increased risk was present,” says Ramachandran Vasan, a professor of medicine at BU’s School of Medicine and the study’s lead investigator and senior author.

Vasan says that study participants who drank soda on a daily basis exhibited an increased risk for developing metabolic syndrome. The syndrome, which doubles a person’s risk of heart disease, is a grouping of cardiovascular disease and diabetes risk factors. These factors include excess waist circumference, high blood pressure, elevated triglycerides, low levels of HDL (good cholesterol), and high blood-sugar levels even on an empty stomach. According to the American Heart Association, more than 50 million Americans have metabolic syndrome.

“The findings are striking,” says Vasan. “Just one soft drink a day increases your risk of developing metabolic syndrome by about 45 percent.”

The study looked at 9,000 middle-aged men and women three times over a four-year period. Compared to participants who drank less than one soda daily, those who drank more had a 31 percent greater risk of developing new-onset obesity, a 30 percent increased risk of developing increased waist circumference, a 25 percent greater risk of developing high blood triglycerides or high fasting blood glucose, measured after an eight-hour fast, and a 32 percent higher risk of having low HDL levels.

Prior studies have linked soda consumption to risk factors for heart disease, but this is the first linking the risk factors to artificially sweetened diet sodas. “We are a little bit cautious to emphasize this, but there is an association,” says Vasan. “We don’t know whether diet soda is causing it. More research needs to be done.”

This study also departs from previous research connecting soda to weight gain in children and adolescents. “In our study the mean age was 53 years old,” says Vasan.

Susan K. Neely, president and chief executive officer of the American Beverage Association, says that the study simply underscores the need for moderation, and the researchers agree that diet and exercise habits could be related to consumption of these products. “People who drink soda also tend to eat more calories, trans fats, and saturated fat and less fiber, and exercise less,” says Vasan. “So it could be that a lifestyle pattern is increasing risk.”

Other possible explanations for the association include the fact that soda is a liquid and liquids don’t fill you up like solids. “Liquids satiate you less than food like salad, so if you drink a large amount of liquids at a meal, you are more likely to eat more at the next meal,” says Vasan. The sweet taste also conditions drinkers to prefer sweeter things, such as cookies, cakes, and candy, which cause weight gain. Even cola’s color could have an effect, because caramel, which gives cola its color, has been associated with inflammation of the tissues and insulin resistance. The high-fructose corn syrup used in soda does not appear to be a factor, because the connection to metabolic syndrome occurs also in drinkers of diet soda, which does not contain the syrup.

“These are theories, which are being debated,” says Vasan. “The bottom line is that it’s an interesting association between soda and increased risk for metabolic syndrome, and we hope doctors will do additional research into the subject.”

Meghan Noé can be reached at mdorney@bu.edu.