A cup of fountain soda being filled

Replacing saturated fat with healthy fats is the main dietary step people take to improve cholesterol and triglyceride levels. But according to a new study published Wednesday in the Journal of the American Heart Association, avoiding soda may also have a positive effect.

Researchers from Tufts University and Boston University wanted to explore how people’s intakes of different beverages might impact dyslipidemia, an unhealthy imbalance of cholesterol and trigylcerides in the blood that increases the risk of heart disease. They looked at nearly 12 ½ years’ worth of data from about 6,000 adult participants in the Framingham Heart Study, a long-term, ongoing research project focused on cardiovascular health.

People who had more than one serving of sugar-sweetened beverages like soda, sports drinks, or presweetened teas each day over the past four years had levels of HDL ("good") cholesterol and triglycerides that may signify an increased risk of heart disease. (A serving was defined as 12 ounces, the amount in a can of soda. But many single-serving soft drinks come in 20-ounce bottles, so you could be drinking more than one serving even if you only have one bottle per day.)

More On Sugar & Health

Compared with those who drank these beverages less than once a month, daily drinkers were 98 percent more likely to have low HDL levels and 53 percent more likely to have high triglycerides. And while the risk was lower in people who had between three and seven sweet drinks per week, there was still an effect. “It’s possible that consuming only three or four sugar-sweetened beverages each week may be increasing your risk factors,” says Kimber Stanhope, Ph.D., R.D., a research nutritional biologist at UC Davis. Diet beverages and 100 percent fruit juice didn't have an effect. 

“This study gives us pause to consider what we are putting in our glasses daily, especially as we age,” says study author Nicola McKeown, Ph.D., nutritional epidemiologist at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University.

While scientists don’t completely understand how sugar-sweetened beverages might impact heart disease risk, studies in humans and animals suggest some possibilities, says McKeown. “Picture an assembly line in your body that creates triglycerides,” she says. Sugar is one of the raw materials your body uses to make them, and eating too much of it may ramp up the body's triglyceride-producing machinery.  

How Drinks Compare

Based on the results of this study and others, for sugary drinks, less is best, says McKeown. “The more sugar-sweetened beverages you consume, the worse the potential impacts on your health.” Other studies have found that sugary drinks increase the risks of being overweight and developing type 2 diabetes. 

But fruit juice and diet drinks may not be good substitutes. Although these beverages didn’t have a consistently negative effect in this study, it's possible that this is because people who drink them may have a healthier lifestyle overall, McKeown says. The study’s analysis does account for this, but she says it isn't possible to completely disentangle these influences, so more research is needed.

In addition, although fruit juice is healthier than sugar-sweetened drinks, the lack of fiber means your body absorbs its natural sugars more rapidly, which may have a negative effect on blood sugar levels. As for diet drinks, other research suggests that evidence that they help control weight, blood sugar levels, or other health problems is limited. Some studies link low-calorie sweeteners to stroke and weight gain.     

Unsweetened flavored seltzer, fruit-infused water, iced herbal tea, and plain old fashioned H20 are all healthy and low-risk ways of quenching your thirst that won’t stoke your sweet tooth—or impact your cholesterol.