Could artificial sweeteners be helping cause the very thing they are supposed to prevent? They may well do so, and you can probably blame your microbiota – those masses of mostly-friendly bacteria that live in your gut. According to a paper by Weizmann Institute scientists that appeared today in Nature, artificial sweeteners not only encourage the wrong kind of bacteria to expand their numbers, they also induce mix-ups in the cross-communication between these bacteria and your body. Those mix-ups can lead to glucose intolerance – the first step toward metabolic syndrome and diabetes. So, ironically enough, if you consume the recommended amounts of zero-calorie drinks, you could begin developing glucose intolerance in just a week. That is what happened to human volunteers who consumed artificially sweetened food and drink for the experiment.
The Weizmann Institute’s Dr. Eran Elinav, who conducted the research together with Prof. Eran Segal, says that this is not really a surprising finding. Your body does not absorb artificial sweeteners – they pass right through you. Even if it did, the human body could not yet have evolved tolerance to the sweeteners – substances that have only existed for about a century. Your gut bacteria, on the other hand, evolve rapidly, and they pretty much eat what you eat, including those zero-calorie drinks.
We have known for a while that the composition of your internal population of bacteria can, among other things, affect your tendency to gain weight, and that diet has an effect on this composition. But this knowledge is still fairly vague: No one can tell you, yet, just what to eat for the most healthful microbiome, or what, exactly, that mix of bacteria will do for you. So the Nature paper makes a pretty strong statement: Your gut microbiota cannot be ignored any longer. Their intimate relationship with your body is vital; its consequences for your health are critical.
The researchers worked with both mouse and human subjects. The mouse research was pretty damning on its own: Mice fed artificial sweeteners (in FDA-permitted doses) developed glucose intolerance while those that had been treated with antibiotics to eliminate their gut bacteria did not. In the meantime, sterile mice that had the microbiota from glucose intolerant mice implanted in their guts quickly developed the same glucose intolerance. Even gut bacteria grown in a lab dish with artificial sweeteners and then implanted in mice could induce glucose intolerance.
The human research was, as is usually the case, a bit more complicated. The findings suggest that some people may not be affected either way by artificial sweeteners, while for many others the effect will be negative. The difference is, again, in the makeup of their gut microbiota. The researchers first discovered these two different patterns in a large trial they have been conducting called the Personalized Nutrition Project (www.personalnutrition.org). The trial, in which hundreds have already participated, aims to figure out how each individual’s mix of heredity, habits and gut microbiota come together to determine how their food will affect them. The ultimate goal of this project, says Segal, is to give people the knowledge they need to avoid such diet-related diseases as obesity, metabolic syndrome, hypertension and atherosclerosis.
The human volunteer experiment backed up these findings. As with the mice, the composition of their gut microbiota changed with that one change in their diets, and for many, this led to the onset (thankfully reversible) of glucose intolerance.
Elinav believes that the widespread use of artificial sweeteners may even be contributing to the global obesity epidemic. In the not so distant future, a personalized nutrition evaluation – including a check of one’s gut microbiota – might be used to recommend the proper diet for avoiding such health problems as artificial-sweetener-induced glucose intolerance.
In the meantime, they suggest you drink water!
Here is a nice video they made at the Wall Street Journal: