By Kate Kelland
Reuters
Scientists investigating the effects of artificial sweeteners in both mice and humans report that consuming these substitutes may increase the risk of developing glucose intolerance, a known precursor to type 2 diabetes. Their research suggests that artificial sweeteners can alter the balance of gut microbes in ways that may raise susceptibility to metabolic disorders.
Eran Elinav of the Weizmann Institute of Science in Israel, who co-led the research, said: “In our studies we found that artificial sweeteners may drive, or contribute to… an exaggerated elevation in blood glucose levels – the very same condition that we often aim to prevent by consuming them.”
Calorie-free artificial sweeteners are commonly used in diet sodas, sugar-free yogurts, desserts and other products. They are frequently recommended as tools for weight management and for preventing or treating diabetes because they provide sweet taste without calories. However, the new findings challenge the assumption that non-caloric artificial sweeteners (NAS) are uniformly beneficial for metabolic health.
Elinav’s team carried out a series of controlled experiments in mice and follow-up studies in humans. The researchers tested three widely used sweeteners—saccharin, sucralose and aspartame—and repeated parts of the work several times to verify their observations.
In the mouse experiments, animals given drinking water supplemented with glucose plus an artificial sweetener developed clear glucose intolerance compared with mice that received water alone or water containing sugar only. The investigators concluded that the adverse effect on glucose regulation was linked to changes in the composition and function of gut microbes induced by the sweeteners.
Findings Inconclusive for Humans
When the team examined human participants, they analyzed gut bacteria from roughly 400 people and observed meaningful differences in the microbial communities of those who habitually consumed artificial sweeteners versus those who did not. The NAS consumers also displayed metabolic markers associated with diabetes risk, including higher blood glucose and signs of glucose intolerance.
To test causality, the researchers recruited seven volunteers who did not normally use artificial sweeteners and placed them on a controlled, high-NAS diet for seven days. After only four days on the regimen, these volunteers showed increases in blood glucose levels and detectable shifts in gut microbiota composition that mirrored the mouse findings.
Writing in the journal Nature, the team stated that their results “indicate that non-caloric artificial sweeteners may exacerbate, rather than prevent, metabolic disorders such as glucose intolerance and diabetes.” They emphasize the potential for NAS to influence metabolic health through alterations in gut microbes.
Independent nutrition and metabolism experts find the results thought-provoking but advise caution before changing public health guidance. Many specialists note that the strongest experimental evidence comes from animal models, and that human data remain preliminary.
Nita Forouhi, program leader at the Medical Research Council’s epidemiology unit at Cambridge University, commented that while the research raises important questions, it does not yet provide sufficient evidence to revise clinical or public-health recommendations regarding non-caloric artificial sweeteners.
Naveed Sattar, a professor of metabolic medicine at the University of Glasgow who was not involved in the study, emphasized two caveats. First, animal findings do not always translate directly to humans. Second, current large-scale epidemiological data have not established a clear link between diet drinks and increased diabetes risk, whereas sugar-sweetened beverages have been associated with higher diabetes incidence in many studies.
Given the global rise in obesity and type 2 diabetes, public-health advice frequently encourages reducing sugar intake and often recommends switching to low- or no-calorie alternatives. The new research suggests this strategy may be more complex than previously thought and highlights the importance of further human studies to clarify how artificial sweeteners affect gut microbes and metabolic health over the long term.
Until more definitive human evidence is available, experts generally advise balancing the potential risks and benefits of artificial sweeteners and focusing on overall dietary patterns that support metabolic health, including reducing excess calories, increasing fiber-rich foods, and maintaining a healthy weight.