Is artificial sweetener harming your microbiome?


In a ground-breaking report in the journal Nature this week (October 9th), Suez et al., report a potential link between artificial sweeteners and glucose intolerance induced by alterations in the gut microbiota. Non-caloric artificial sweeteners (NAS) were developed over 100 years ago as a low calorie substitute for sugar and are regarded as safe for human consumption by the FDA. As such, they are found in a plethora of “diet” and “sugar-free” foods and drinks.

The group tested the effects of three NAS in mice. They found that the three sweeteners increased glucose intolerance in mice when included as a regular part of their diet. Intriguingly, this glucose intolerance was ameliorated when mice were treated with antibiotics for 4 weeks, suggesting that the observed glucose-intolerance was induced by changes in the host microbiota. Indeed, changes in the gut bacteria were recorded in the mice that developed glucose intolerance. The observed changes in bacterial taxa were consistent with those associated with type 2 diabetes in humans.

They further confirmed this finding by transferring the microbiota from these now glucose intolerant mice to mice raised germ-free. Subsequently, these animals also developed increased glucose intolerance, lending weight to the hypothesis that the induced glucose intolerance was microbiome-driven.

When the group cultured the stool retrieved from healthy mice and cultured it in the presence of the sweetener saccharin they observed similar changes to the microbiota composition as mice fed saccharin. Transferring this lab-cultured microbiota into germ-free mice again induced glucose intolerance.

Finally, the group assessed the effect of long-term consumption of artificial sweeteners on humans from an on-going clinical nutrition study involving 381 non-diabetics participants. From this analysis they found numerous associations between long-term NAS consumption and increased weight, waist-to-hip ratio (an indicator of abdominal obesity), increased fasting blood glucose levels and increased glycosylated hemoglobin levels (a measure of blood sugar control).

Artificial sweeteners were introduced to reduce caloric intake and help normalize blood glucose levels. Ironically they may have the opposite effect.


Researchers tested three sweeteners– saccharin, sucralose, Aspartame for effect on glucose tolerance.

Aspartame had the smallest effect on glucose tolerance.

Saccharin had the greatest effect on glucose tolerance.

Effects were mild but significant.

Sweetener consumption was associated with changes in the gut microbiota consistent with those observed in type 2 diabetes.


Saccharin had the largest effect and may be the more concerning sweetener. The most widely used (especially in soft drinks), aspartame had a much smaller effect.

Confirmation study in humans was small, making it difficult to judge the significance.


NAS – Non-caloric artificial sweetener


Suez J. et al., (2014) Artificial sweeteners induce glucose intolerance by altering the gut microbiota. Nature. 514 pp181-186.