A few weeks ago, we posted about a new study about artificial sweeteners and their potential to affect the microbiome, potentially leading to glucose intolerance for some people. We’ve gotten a lot of questions, so we reached out to Suzanne Devkota, PhD, post-doctoral fellow, who studies the microbiome at Joslin Diabetes Center, to get some answers.
In the late 1800s, a Johns Hopkins University researcher discovered that a chemical compound he’d been working on earlier that day was sweet to taste, introducing the world to its first artificial sweetener—saccharin. Since then, six other no-cal, artificial sweeteners have been brought into the world’s food supply in attempts to combat the waist-line-ballooning effects of consuming too much sugar. But newly announced research out of Israel suggests that the thing many people use to try and lose weight might be what’s making some of them keep it on.
Researchers from the Weizmann Institute of Science in Israel published a paper in the journal Nature last week detailing a thorough investigation into the effects of saccharin on the microbiome of humans. They state that consumption of saccharin specifically, and potentially other artificial sweeteners, can disrupt the delicate balance of the little bacteria living in human guts.
“This study addresses a question I have been asked many, many times regarding how artificial sweeteners affect the microbiome,” says Dr. Devkota. “People are very interested in how not just diet, but dietary additives affect gut health. The findings from this study were quite interesting yet do not warrant anyone to start throwing their sweeteners in the trash.”
The Israel study was the first of its kind, she cautions, and as with any good science the results will need to be replicated in other laboratories before changing any national dietary recommendations. “Much more work needs to be done on the topic,” she says. “While this was the first study to show effects of sweeteners on the gut microbiome, many aspects of the experimental design and results are curious and absolutely warrant repeating before we make any behavior modifications.”
Dr. Devkota continues to say that while these preliminary results are worth delving into more deeply, the study was mostly conducted in rodents and the human sample size was too small to be considered representative of a major population.
The researchers started their work in rodents, testing the metabolic reactions to plain water versus water laced with artificial sweeteners or glucose. The group ingesting saccharin showed the greatest negative metabolic effects. They continued comparing the super-sweet sugar substitute to glucose, and they showed significant metabolic changes that all related to type 2 diabetes.
But how could eating something calorie-free be so harmful to the metabolism? They started thinking that the saccharin somehow altered the microbiome, those colonies of bacteria that make their homes in the digestive systems of all animals. To test this hypothesis, they transplanted the microbiome of the saccharin-eating mice into “clean-slate” mice that had no microbiome. And even though the “clean-slate” mice had never eaten a molecule of saccharin, they exhibited the same metabolic problems.
When the researchers looked at the colonies that made their home in each microbiome they noticed more than 40 groups of bacteria in the saccharin-consuming mice had changed significantly from before they started their saccharin-filled diets.
Next, the researchers wanted to see if the same held true in humans. They reviewed data from a long-term nutrition study that monitored the food participants ate over time and recorded various health measures. They saw that throughout the 381 people, the more saccharin a person consumed the greater their risk for metabolic defects: increased fat between the organs in the stomach (also known as visceral fat), higher fasting blood glucose, higher A1C and impaired glucose tolerance, to name a few.
They finished off the series of experiments by feeding seven healthy volunteers the FDA’s maximum daily allowance of saccharin—the equivalent of about 10 packets of Sweet ’n Low– for 6 days straight, measuring their metabolic responses through a continuous glucose monitor and daily glucose tolerance tests. By the end of the week, four of the seven participants experienced poorer glycemic responses than they had during the first few days of the study.
When they tested the microbiomes of the negatively-affected human participants they saw similar changes to what they had seen in their earlier study with rodents. After prolonged exposure to a lot of saccharin, these participants saw their microbiomes morph into microbial communities previously associated with type 2 diabetes.
It’s important to note that not all of the participants experienced negative effects in their metabolism. The researchers believe the three people who fared well over the seven days of the experiment started with a different microbiome than the people whose metabolisms declined, meaning their microbiomes may be either less susceptible to such metabolic changes or have factors that protect against the effects of saccharin.
So what do these findings mean for people who have made saccharin and other artificial sweeteners a part of their daily weight maintenance routine? Keep in mind, the seven study participants were fed the maximum amount of saccharin the FDA considers healthy. Even if you do consume saccharin-containing foods, you probably aren’t eating up to that amount.
“With diet, everything in moderation is always best. If you drink a can or two of diet soda per day and put a little sweetener in your coffee, you are fine,” says Dr. Devkota. “If you’re drinking ten cans a day, regardless of this study, you may want to cut back.”