A new review by Tufts University researchers presents comprehensive and convincing research linking common sugar substitutes with metabolic disturbances that begin in the gut and then flow throughout the body. It also highlights issues of food-label transparency in the US.
An analysis of findings from 21 randomized clinical trials involving adults found that artificial sweeteners raised fasting insulin and HbA1c – a known biomarker of long-term blood sugar control – opening the door to increasing insulin sensitivity.
“What makes our analysis notable is that by focusing on non-caloric comparators, we better isolated the direct physiological effects of the sweeteners themselves, not the calories they replace,” says first author Meng Wang, a research assistant professor at Tufts University. “When pooling findings from individual trials, we see signals that these compounds may have metabolic harms.”
And the issues, they hypothesize, begin with how these sugar substitutes interact with the gut microbiome.
We've covered individual studies that have linked artificial sweeteners to microbiome disturbances before. This includes research from last year that found consistent diet soda consumption was tied to a huge spike in diabetes risk.
In addition to the 21 trials the researchers assessed, they also looked at large observational studies. Again, sweeteners were implicated in poor health outcomes – in this case, a much higher risk of developing cardiometabolic diseases.
While the team notes that there are limitations to these types of studies – people who are already at a heightened risk of cardiometabolic diseases might be more likely to choose diet or sugar-free foods and beverages – these observational findings support the trial outcomes.
Of specific concern, the researchers add, is how artificial sweeteners appear to alter the microbial makeup of the gut and impede its function. This sort of interference has a flow-on effect that goes well beyond the microbiome.
One of the issues with investigating artificial sweeteners and human health has been the lack of longitudinal research. Much like ultra-processed foods and high-fructose corn syrup, the world's consumption of sugar alternatives has been a relatively recent trend, in science-research terms.
“The rapidly increasing use of these sweeteners has outpaced our understanding of their long-term health effects,” says senior author Dariush Mozaffarian, a cardiologist and director of the Food is Medicine Institute at Tufts University. “Until we know more, caution is needed.
"If you’re replacing large amounts of added sugar in your diet, such as in multiple servings of soda, these low-calorie sweeteners may be a better alternative," he adds. "But we can’t simply assume they are safe and innocuous, and avoiding them whenever possible appears a prudent choice.”
Another issue the team highlights is how, in the US, food manufacturers are not required to label how much artificial sweetener is in a product. So this has hindered scientists from being able to study real-world consumption of what the team calls "non-nutritive sweeteners" (NNS) and their potential health impacts.
"Future clinical trials of physiologic effects and molecular mechanisms will strengthen interpretations and causal inference," they note in the study. "Given potential for harm, caution is warranted for the use of NNS."
The study was published in the journal Current Atherosclerosis Reports.
Source: Tufts University
Fact-checked by Mike McRae
