Some artificial sweeteners may alter the microbiota, affect blood glucose control

A recent study suggests that the microbiome changes in response to human consumption of non-nutritive sweetener may induce glycemic changes in consumers in a personalized manner.
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What is already know
Replacing dietary sugar with non-nutritive sweeteners (NNS) such as aspartame and stevia is one of the most common strategies in combating obesity and high blood glucose levels. Although scientists have long thought that NNS have no effect on the human body, recent studies suggest that these substances may have negative health impacts.

What this research adds
Researches recruited 120 people who avoid NNS in their lives, and divided them into six groups: four groups ingested either aspartame, saccharin, stevia, or sucralose, one control group received glucose, and another control group received no supplement. People who consumed NNS showed changes in their gut microbiota and the microbial metabolites in their blood. The changes in gut microbes correlated with alterations in people’s glycemic response, or the post-meal spike in blood glucose levels. Such changes in the microbiota did not occur in the control groups. Germ-free mice that received the microbiota of people who consumed NNS and had a high glycemic response developed alterations that resembled those of the human donors.

Conclusions
The findings suggest that, in some people, NNS can change the microbiota in ways that alter a person’s glycemic response.

Replacing dietary sugar with artificial sweeteners such as aspartame and stevia is one of the most common strategies in combating obesity and high blood glucose levels. However, new findings suggest that, in some people, these sweeteners can change the microbiota in ways that alter a person’s glycemic response.

The work, published in Cell, underscores the need to understand the long-term impact of artificial sweeteners. “We need to raise awareness of the fact that non-nutritive sweeteners are not inert to the human body as we originally believed,” says study co-senior author Eran Elinav at the Weizmann Institute of Science. “With that said, the clinical health implications of the changes they may elicit in humans remain unknown and merit future long-term studies.”

Scientists have long thought that aspartame, stevia and other non-nutritive sweeteners (NNS) have no effect on the human body. However, recent studies suggest that these substances may have negative health impacts.

Previous work by Elinav’s team suggested that NNS induce glucose intolerance in mice by altering their gut microbiota. This time around, Elinav and his colleagues assessed the effects of NNS in humans.

Glucose tolerance

The researches recruited 120 people who avoid NNS in their lives, and divided them into six groups: four groups ingested either aspartame, saccharin, stevia, or sucralose, one control group received glucose, and another control group received no supplement. All NNS were given as sachets containing a fraction of the acceptable daily intake of each of the supplements.

Study participants wore a glucose monitor that assessed their sugar blood level for 29 days and recorded their food intake and physical activity using a smartphone application. All participants took glucose tolerance tests and provided stool and oral microbiota samples on predetermined days. 

Unlike controls, people who consumed NNS showed changes in their gut microbiota and the microbial metabolites in their blood. The changes in the microbes correlated with alterations in people’s glycemic response, or the post-meal spike in blood glucose levels. Saccharin and sucralose significantly impacted glucose tolerance in healthy adults, the researchers found.

Personalized effects

To determine whether changes in the microbiota were responsible for the alterations observed in people’s glycemic responses, the researchers transferred microbial samples from the study participants into germ-free mice.

Mice that received microbes from people who consumed NNS and had a high glycemic response developed alterations that resembled those of the human donors. Such effects were not observed in animals that received microbes from people who had low glycemic responses.

“These results suggest that the microbiome changes in response to human consumption of non-nutritive sweetener may, at times, induce glycemic changes in consumers in a highly personalized manner,” Elinav says.

The findings also indicate that the effect of NNS on gut microbes may lead to glycemic alterations in some, but not all consumers, depending on their individual microbiotas and the type of artificial sweeteners that they consume.