The study compared overweight people with normal sugar metabolism to see how they reacted when they were given either water or sucralose—about as much as is in one can of diet soda—to drink before a glucose challenge test, which involves drinking a glucose mixture and then having blood taken at multiple intervals. Researchers found a kind of insulin-and-blood-sugar roller-coaster scenario. People’s blood sugar levels peaked higher if they got sucralose, rather than water, before the glucose challenge test. Insulin levels also climbed higher. And, a few hours into the test, at the lowest blood sugar point, sucralose consumption led to lower blood sugar levels than did water, which can set the stage for carb cravings. “Everyone got the same amount of glucose, both times, but their bodies secreted much more insulin when they got sucralose first,” says M. Yanina Pepino, PhD, the study’s main researcher.
Insulin is needed for the body to use sugar for energy, but too much is harmful, Dr. Pepino says. High blood levels of insulin keep fat from being broken down for energy, making it hard to lose weight. And chronically high insulin levels can lead to insulin resistance, a precursor to type-2 diabetes.
Does that mean that people who drink diet soda all the time are setting themselves up for type-2 diabetes? No one knows, Dr. Pepino says.
However, in two large population studies, consumption of non-nutritive sweeteners (think all of those pastel packets at your local coffee shop) has been associated with increased risk for type-2 diabetes or obesity. One study, the Multi-Ethnic Study of Atherosclerosis (MESA) found that at least daily consumption of diet soda was associated with significantly greater risk for metabolic syndrome or type-2 diabetes, compared to non-users. Another, the San Antonio Heart Study, found that having more than 21 artificially sweetened beverages a week was associated with the risk for overweight or obesity doubling, compared with non-users.
Of course, an association does not mean that artificial sweeteners were the cause of these problems, Dr. Pepino says. Still, her study points to a possible reason why they might indeed be linked. Not all artificial sweeteners are alike in their metabolic effects, either, she says. (She hopes to next test aspartame.)
As for practical advice, she says: “I still think diet drinks are preferable to sugar-sweetened drinks, but I would suggest that people think more about just having water to drink, especially if they are trying to lose weight or avoid diabetes. Some people sip diet drinks all day long thinking they are just like water, but they’re not. I would limit diet drinks to no more than one or two a day.”
More from Prevention: 10 Crazy Ways To Sweeten Without Sugar
