The premise: Many soda drinkers opt for diet over regular, thinking that the zero calories and zero sugar makes the drink a healthier option. But the scientific evidence backing up that idea is lacking. In fact, a 2005 study reported that people who drink diet soda instead of regular don’t lose any extra weight. Rather, they gain weight. Now, a new nine-year study finds a connection between drinking diet soft drinks and an increased risk of heart attack and stroke.
The set-up: Researchers gathered 2,465 subjects. The average age was 69 and about two-thirds of the participants were women—but the findings are still applicable to you. “We didn’t see any interaction with age or sex,” says study researcher Hannah Gardener, ScD, an epidemiologist at the University of Miami Miller School of Medicine. “Therefore there’s no reason why the results would be different for younger, male subjects.”
At the start of the study, people were asked to document what foods and beverages they consumed and how often they consumed them. They were asked about their exercise routines and whether they smoked or drank alcohol. And the participants had physical checkups.
With the preliminary research in: 901 participants said they never drank soda or drank it less than once a month, 282 said they drank at least one regular soda daily and 116 reported they drank at least one diet soda a day.
The results: Over the next nine years, those who drank diet soda daily were 48 percent more likely to have a heart attack or stroke, compared with those who rarely drank soda. There was actually no risk increase for cardiovascular disorders among the daily drinkers of regular soda.
“We had a strong bias for conducting the study, as other diet soda studies have suggested an association between diabetes, weight gain, coronary heart disease and other ailments, but we were surprised to find the strength of the results,” says Gardener.
A few flaws in the study are worth noting: Participants were only asked about the soda habits at one point (they may have changed habits at some point during the nine years) and there’s no information about which soft drinks were being consumed. And even though the researchers tried to consider for risk factors that that could skew the results, they couldn't account for everything.
The takeaway: Despite the overwhelming results, the study doesn't prove cause and effect. Meaning, it’s too early to recommend swapping a diet soda for a regular calorie-heavy soda. “I actually don’t think you should drink any soda at all,” Gardener suggests. “I’d always recommend a glass of water over any other beverage.”