It found that commonly used artificial sweeteners consumed by female mice transfer to pups in the womb and later through milk, harming their development. The sweeteners affected the composition of bacteria in the gut of the pups, making them more vulnerable to developing diabetes, and greatly reduced the liver’s capacity to neutralize toxins. 

The discovery was serendipitous, not part of the original study, says John Hanover, the senior author and a cell biologist at the NIH National Institute of Diabetes and Digestive and Kidney Diseases. The main study looked at how a high sugar diet in the mother turns genes on and off in the developing offspring.

It compared them with mothers fed a low sugar diet, replacing sugar with a mix of sucralose and acesulfame-K (AK), two non-nutrient artificial sugars that are already used extensively in our food products and thought to be safe. 

While the artificial sweeteners had little effect on the mothers, the trace amounts that were transferred through the placenta and milk had a profound effect on the pups. Hanover believes the molecules are changing gene expression during a crucial, short period of development. 

 “Somewhat to our surprise, we saw in the pups a really dramatic change in the microbiome” of those whose mothers were fed the artificial sweeteners, Hanover told leapsmag. “It looked like the neonates were much, much more sensitive than their mothers to the sucralose and AK.” The unexpected discovery led them to publish a separate paper. 

“The protective microbe Akkermansia was largely missing, and we saw a pretty dramatic shift in the ratio of two bacteria that are normally associated with metabolic disease,” a precursor to diabetes, he explains. Akkermansia is a bacteria that feeds on mucus in the gut and helps remodel the tissue to an adult state over the first several months of life in a mouse. A similar process takes several years in humans, as the infant is weaned off of breast milk as the primary food source. 

Another problem the researchers saw in the animals was “a particularly striking change in the metabolism of the detoxification systems” in the liver, says Hanover. A healthy liver is dark red, but a high dose of the artificial sweeteners turned it white, “which is a sign of massive problems.” 

The study was conducted in mice and Hanover cautions the findings may not apply to humans. “But in general, the microbiome changes that one sees in the rodent model mimics what we see in humans…[and] the genes that are turned on in the mouse and the human are very similar.” 

Hanover acknowledges the quantity of artificial sweeteners used in the study is on the high end of human consumption, roughly the equivalent of 20 cans of diet soda a day. But the sweeteners are so ubiquitous in consumer products, from foods to lipstick, and often not even mentioned on the label, that it is difficult to measure just how much a person consumes every day. 

The good news is the body seems to remove these artificial sweeteners fairly quickly, probably within a week. Until further studies provide a clearer picture, women who want to err on the side of caution can choose to reduce if not eliminate their exposure to artificial sweeteners during pregnancy and breastfeeding.