• A new review analysed several studies on the effects of artificial sweeteners.
• It was observed that sweeteners interfere with blood sugar control and disrupt metabolism.
• Researchers advise caution in consuming artificial sweeteners, avoiding them where possible.

A growing number of studies suggest that artificial sweeteners and non-nutritive sweeteners (i.e. low-calorie or calorie-free) can disrupt our metabolism. Several of these have been brought together in a new review and meta-analysis conducted by researchers at the Food is Medicine Institute at Tufts University and published in Current Atherosclerosis Reports.

Sweeteners harmful to metabolism: the hypothesis is that they alter the gut microbiota

Across 21 randomised clinical trials conducted on adults, researchers observed that artificial sweeteners and other low-calorie sweeteners, compared with water or a placebo, raised fasting insulin and HbA1c — a marker of long-term blood sugar control — and showed a tendency towards worsening insulin sensitivity.

"What makes our analysis relevant is that, by focusing on non-caloric comparators, we were better able to isolate the direct physiological effects of the sweeteners themselves, rather than of the calories they replace," said lead author Meng Wang. "Looking at the results of individual studies, we see signals that these compounds may have harmful effects on metabolism."

According to the researchers, one possible explanation for these effects, based on current evidence, concerns the gut microbiota. Non-nutritive sweeteners generally pass through the intestine and come into direct contact with the bacteria present there. One clinical study examined found that certain low-calorie sweeteners alter both the composition and function of the gut microbiota.

In addition to the randomised trials, the researchers examined large observational studies, which in general found a link between the consumption of non-nutritive sweeteners and a higher risk of developing cardiometabolic diseases. Despite the limitations of these studies, and the fact that different sweeteners may have different effects on health, the researchers state that the body of available evidence is cause for concern.

Artificial sweeteners: "Avoid them where possible".

"The rapidly growing use of these sweeteners has outpaced our understanding of their long-term health effects," said Dariush Mozaffarian, one of the study's authors. "Until we know more, caution is warranted." According to the researchers, sweeteners may be a better alternative to large amounts of added sugars in the diet, but one cannot simply assume they are safe and harmless — and it is prudent to avoid them where possible.