Thursday, September 18, 2014

No free lunch: No calorie sweeteners shown to cause gut changes that induce glucose intolerance

No-calorie sweeteners have proven to be relatively useless in the fight against obesity, despite what the food industry may tell you.  In a new study published in Nature, researchers provide evidence that no-calorie sweeteners can induce metabolic changes that lead to glucose intolerance in both mice and humans.  This study found that the changes in glucose tolerance come about from shifts in gut bacteria.

The mouse arm of this study started by feeding mice a 10% solution of either saccharin, aspartame, or sucralose in place of drinking water and comparing their glucose tolerance to control mice given either water alone or a 10% glucose solution.  After 11 weeks, the glucose tolerance in the mice given the artificial sweetener was worse than the mice given water or even glucose.  Previous research has shown that certain no calorie sweeteners can alter the gut microbiome, so the researchers gave mice a 4 week course of antibiotics to wipe out the microbiome.  The result...Glucose tolerance returned to normal.

To make certain that the effects were due strictly to changes in the gut microbiome, researchers transplanted feces from the mice given saccharin in to germ-free mice who had not had the sweetener.  Within a week, the germ-free mice had the same changes in glucose tolerance as those who consumed the no-calorie sweetener.  Looking at the fecal samples, researchers found changes in the microbiome that mirrored changes in the microbiome of humans that eat no-calorie sweeteners.  Furthermore, a follow-up with 7 humans with no history of using no-calorie sweeteners who were fed saccharin at the maximum daily limit allowed by the FDA found that 4 of the subjects had poorer glucose tolerance after 7 days and an altered gut microbiome that, when transplanted in to mice, resembled the one seen in mice fed saccharin.

This study brings up a few important points.  While the dosage of no-calorie sweetener was high, it was within FDA limits.  So while you may not consume these sweeteners at the level seen in these studies, the point is that they aren't entirely benign.  Furthermore, relying on these sweeteners as a crutch to kick a sweet tooth may not be in your best interest, especially if you are diabetic.  Secondly, some people did not respond negatively to the no-calorie sweetener.  An important question to answer would be whether or not Type 2 diabetics, who have poor glycemic control in the first place, are more likely to be susceptible to poorer glycemic control from these sweeteners due to their microbiome.  I would be willing to bet that people with Type 2 diabetes are more likely to rely on no-calorie sweeteners because they "have no direct effect on blood glucose".  Unfortunately, they apparently have an indirect effect on blood glucose that is just as bad as a direct one.

Finally, even though the people who weren't affected by the artificial sweeteners were in the minority, the fact that their glucose tolerance wasn't affected, nor was their microbiome, points to no-calorie sweeteners being benign for them.  As is a frequent topic in this blog, an individualized approach to health and diet is always the best approach.