Common artificially-sweetened foods. Photograph by Graham Turner, The Guardian.

The communities of microorganisms that live on and inside our bodies, collectively known as the microbiome, help humans carry out basic physiological processes – from synthesizing essential vitamins to defending against infection. However, many important microbial functions are not yet entirely understood, particularly the role played by trillions of symbiotic bacteria that call our digestive tract home.

Common artificially-sweetened foods. Photograph by Graham Turner, The Guardian.
Common artificially-sweetened foods. Photograph by Graham Turner, The Guardian.

Intestinal microbes impact weight gain, dictate food allergies, and activate neural pathways that regulate stress and depression. They eat what we eat, whether it is a cheeseburger, a kale salad, or in today’s world, an extra large diet soda. Historically, non-caloric artificial sweeteners have been written off as having little impact on our bodies since they cannot be metabolized. A recent study published in Nature by Drs. Eran Segal and Eran Elinav now suggests otherwise. Besides making food taste sweeter, some of these molecules might cause changes in gut microbiota that disrupt the body’s ability to control blood sugar. Mice regularly fed artificial sweeteners (saccharin, aspartame, or sucralose) developed marked intolerance to glucose. This ill effect was reversed with antibiotics, which killed many digestive bacteria. Human subjects were then fed the maximum allowed daily dose of saccharin over the course of one week. Four of the seven humans studied experienced dramatic spikes in blood sugar as well as shifts in the composition of their gut microbiome. The authors concluded that artificial sweeteners might be contributing to the obesity epidemic, and warn against their current widespread use.

These findings are compelling, but far from conclusive. One shortcoming of the study is that the data were largely collected in mice, and thus may not directly translate to humans. The human component is also difficult to interpret, due to the small number of subjects as well as the variability in their responses to unnaturally high doses of saccharin. Even though more work needs to be done on sugar substitutes before a true recommendation can be made, it is important to consider our microbiota. The microbes in our bodies are probably up to a lot more than we think.

Acknowledgments: Many thanks Jonathan Kotula, PhD (Systems Biology) and Daria Van Tyne, PhD (Microbiology and Immunobiology) at Harvard Medical School for their expertise and detailed insights on the topic.

Managing Editor: Laura L. Smith

Additional Reading:

Artificial Sweeteners May Promote Diabetes, Claim Scientists (The Guardian)

Do Artificial Sweeteners Raise Diabetes Risk? (British National Health Service)

Artificial Sweeteners May Disrupt Body’s Blood Sugar Controls (New York Times)

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