A new review and meta-analysis from Tufts University researchers, published in Current Atherosclerosis Reports, compiles data from 21 clinical trials involving adults. These studies compared the effects of artificial and low-calorie sweeteners to non-caloric controls like water or placebo, revealing consistent trends in metabolic markers.
The analysis found that artificial sweeteners raised fasting insulin levels and HbA1c, a measure of long-term blood sugar control. Insulin sensitivity also showed a troubling decline in some cases. Researchers argue these findings isolate the direct impact of sweeteners, rather than the calories they might replace. Meng Wang, a research assistant professor at Tufts’ Friedman School of Nutrition Science and Policy, said, “We see signals that these compounds may have metabolic harms.”
One theory centers on the gut microbiome. Non-nutritive sweeteners pass through the digestive system, interacting with gut microbes. In one trial, low-calorie sweeteners altered both the composition and function of gut bacteria. This could explain why some studies link sweetener use to higher risks of cardiometabolic diseases, though observational research has limitations. People already at risk for such conditions may be more likely to choose these products, complicating cause-and-effect analysis.
The review also highlights a gap in US labeling policies. While manufacturers must list non-nutritive sweeteners in ingredient lists, they are not required to specify quantities. This omission hampers efforts to assess intake levels in population studies. Study senior author Dariush Mozaffarian, a cardiologist and director of Tufts’ Food is Medicine Institute, said, “Until we know more, caution is needed.”
Related: Team solves mystery of flocking birds, fish schools movement
Mozaffarian noted that while low-calorie sweeteners might be preferable to high-sugar alternatives in some cases, they should not be assumed harmless. “Avoiding them whenever possible appears a prudent choice,” he said. The study calls for more randomized trials to explore both health risks and the biological mechanisms involved, which they believe is essential for a full understanding.
For now, the findings suggest that the body’s response to artificial sweeteners is more complex than previously thought. Current evidence does not prove causation but indicates the need for further investigation, which the researchers consider necessary.
Consumers may want to reconsider how they use these products, especially in large quantities. The study does not advocate for outright avoidance but highlights the importance of balancing potential benefits with unknown long-term effects. As the use of sweeteners continues to rise, understanding their full impact on health remains a priority for scientists and policymakers alike, and they are working to address this issue.