The 'Health Halo' of Artificial Sweeteners Is Challenged
Artificial sweeteners are marketed as a healthier alternative to sugar, especially for people trying to manage their weight or lower their risk of diabetes. Because they contain few or no calories, they are widely assumed to help the body control blood sugar. However, a new review of clinical trials suggests that the picture may be more complicated.
Beyond Sugar Comparisons: A More Rigorous Approach
For decades, testing of sugar substitutes mostly stacked them against sugar itself. That comparison favors the substitute, because dropping sugar also drops calories, and fewer calories improve blood sugar on their own. To remove this bias, Professor Meng Wang of Tufts University and her colleagues combined data from 21 randomized clinical trials that compared sweeteners with calorie-free options such as water or a placebo.
Across those trials, people using the sweeteners ended up with higher fasting insulin and higher HbA1c, a marker of long-term blood sugar control, than those in the comparison groups. Insulin sensitivity, which reflects how readily sugar is cleared from the bloodstream, also worsened, although the evidence was weaker.
Potential Mechanisms: Gut Bacteria and Cardiovascular Risk
One explanation for the effect sits lower down, in the gut. Unlike sugar, many sweeteners are not fully absorbed in the upper digestive tract. Because of this, they travel onward and meet the trillions of bacteria that make up the gut microbiome. A 2022 trial tested that idea directly: researchers gave 120 healthy adults common sweeteners for two weeks, then profiled their gut bacteria. Two of them, saccharin and sucralose, measurably worsened how the volunteers processed a dose of sugar.
Furthermore, erythritol, a sugar alcohol common in keto and zero-sugar products, acts through a route that has little to do with gut bacteria. A 2023 study linked higher blood levels of erythritol to an increased risk of heart attack, stroke, and blood clots.
Expert Advice: Caution, Not Panic
Despite the concerning findings, experts emphasize that this does not make sugar safer. For someone drinking several sodas a day, swapping in a low-calorie version still cuts a large load. However, the evidence now suggests these ingredients are not as metabolically inert as they were long assumed to be. Dariush Mozaffarian, a cardiologist at the Food is Medicine Institute at Tufts, stated: 'We can't simply assume they are safe and innocuous, and avoiding them whenever possible appears a prudent choice.'