We’ve known for a while that zero-calorie sweeteners can cause health problems. But for many, the trade-off seems worth it to prevent sugar-linked diseases like diabetes and obesity. Unfortunately, new research is suggesting artificial sweeteners may actually contribute to these conditions over time.

Today, zero-calorie artificial sweeteners are one of the most common food additives in the world. Researchers say that switching from regular to diet soda is like getting ‘out of the frying pan, into the fire.’

“Despite the addition of these non-caloric artificial sweeteners to our everyday diets, there has still been a drastic rise in obesity and diabetes,” says lead researcher Brian Hoffmann, of the biomedical engineering department at the Medical College of Wisconsin and Marquette University. “In our studies, both sugar and artificial sweeteners seem to exhibit negative effects linked to obesity and diabetes, albeit through very different mechanisms from each other.”

Hoffmann’s study, presented at the recent American Physiological Society annual meeting at the 2018 Experimental Biology conference, is the largest tracking of biochemical changes in the body after consumption of sugar and sugar substitutes. The researchers further studied the impact of zero-calorie sugar substitutes on vascular health. Tests were conducted on both rats as well as human cell cultures.

Different groups of rats were fed diets rich in glucose and fructose (kinds of sugars), and diets rich in aspartame or acesulfame potassium (common zero-calorie artificial sweeteners). After three weeks of these diets, researchers compared the concentrations of biochemicals, fats and amino acids in the blood samples collected to the concentrations found in pre-study samples and foud differences that suggest sugar substitutes change the way the body processes fat and gets its energy. They also found acesulfame potassium accumulated in rats’ blood; in higher concentrations acesulfame potassium can have a harm the cells lining blood vessels.

“We observed that in moderation, your body has the machinery to handle sugar; it is when the system is overloaded over a long period of time that this machinery breaks down,” Hoffmann says. “We also observed that replacing these sugars with non-caloric artificial sweeteners leads to negative changes in fat and energy metabolism.”

So it comes down to the lesser of two evils. Unfortunately, the researchers say the findings aren’t clear-cut enough to guide decisions.

“It is not as simple as ‘stop using artificial sweeteners’ being the key to solving overall health outcomes related to diabetes and obesity,” Hoffmann says. “If you chronically consume these foreign substances (as with sugar) the risk of negative health outcomes increases. As with other dietary components, I like to tell people moderation is the key if one finds it hard to completely cut something out of their diet.”