Artificial sweeteners–effect on the human gut bacteria

Before you pop the tab off that next diet soda and enjoy its bubbly, sweet sensation, you may want to rethink its effects on your body. A new study published this past September by Suez and colleagues suggests that non-caloric artificial sweeteners (NAS) are not as harmless to human health as previously thought. In fact, these sweeteners can actually increase the risk of getting diabetes later in life.

Researchers at the Weizmann Institute of Science in Israel discovered a significant decrease in glucose tolerance in mice who had consumed NAS’s versus mice who had not. The data illuminated how artificial sweeteners can alter the composition of our gut bacteria, which control how well we metabolize dietary sugars. The study continues research in a field that had previously shown that patients with diabetes, glucose intolerance and obesity had different gut microbiota than patients who did not. These studies suggested the possibility that diet soda consumption is detrimental to human metabolism, but as University of Chicago pathologist Cathryn Nagler points out, none of them had “pinpointed a microbe-mediated mechanism” by which artificial sweeteners could cause these symptoms.

Diet sodas have been around since the 1950s when a New York company branded “No-Cal,” a sugar free ginger ale customized to allow diabetics to enjoy soda. Since then, however, many non-diabetic consumers have grown to love diet sodas for their purported health benefits. On a given day, about 20 percent of Americans over the age of two consume diet soda, with over half drinking more than 16 oz. (one can). As of 2012, over 29.1 million Americans are reported to suffer from diabetes, with an additional estimated eight million undiagnosed, according to the American Diabetes Association. Knowing the effects of artificial sweeteners can lower the risk of type two diabetes and help diabetics avoid harmful foods.

What does gut bacteria have to do with this? As it turns out, bacteria in the human digestive tract are key players to in the proper digestion and absorption of nutrients from food. However, a careful balance of the right bacteria is needed to maintain a properly functioning system.

In the recent study by Suez et al., mice were given differing solutions of water, sugars, and non-caloric artificial sweeteners (NAS’s) in their water bottles for 11 weeks. The results showed that the experimental group of mice, given NAS water, had significantly higher blood-glucose levels compared to both the water and sugar control groups. Furthermore, the NAS-consuming mice developed a significant increase in glucose intolerance. The results were consistent among mice fed a normal diet and mice fed a high-fat diet.

To confirm that the effects on glucose tolerance and blood-glucose levels were due to the changed state of the gut microbiota, researchers followed up with two studies. In one, the scientists administered four weeks of antibiotics to the symptomatic mice, changing and eliminating the gut microbiota composition, and saw a reversal of symptoms. Second, using non-antibiotic treated mice, researchers transplanted the feces (and microbiota) of NAS treated mice to the guts of the sugar-consuming mice. The latter mice developed similar symptoms within six days. Together, these data demonstrated that the gut “microbiome” is critically important to glucose tolerance, and can be altered in a negative way by consumption of NAS’s.

The researchers wanted to see if the results would translate to human populations as well. 381 non-diabetic volunteers documented their diet and consumed NAS’s regularly, exhibiting the same higher glucose levels, glucose intolerance and changed gut microbiota as the mice studies. In another study, seven healthy young volunteers with no history of NAS consumption repeated the experiment, and found that those who had no response had no change in their gut profiles either. Two of these non-responders had their feces transplanted into germ-free mice, which also exhibited no response, confirming that microbiota changes leads to the changes in metabolism health.

It is hoped that this study can enlighten soda drinkers the next time they walk up to that Pepsi fountain and have to make a decision: diet or regular? The next time you fix your eyes on that beloved soda and tell yourself to go for that ‘healthier’ diet version sitting next door–before you deny yourself the pleasure of pure-sugared pop you may want to rethink if such noble sacrifices are really all that necessary. Better yet, why not go with the water just to be safe?