The topic of nutrition is one that generates constant conversation and discussion, especially when it relates to trying to "find the cause of___." A recent area of interest has been the research related to the microbiome and the gut microbiota, and how they play a role in disease, metabolism and weight.
As a Registered Dietitian I am not a microbiome researcher but certainly how the gut, and the bacteria in it, works is very important to overall nutrition and health so I do pay attention to evolving research. One area that is a "hot" topic of research is whether low calorie sweeteners have an impact on the gut. While there have been many studies in the last few years, one seemed to really create "conversation." A study by Suez et al. reported that low calorie sweeteners increase the risk of glucose intolerance, the problem is – the study had some flaws.1 Let’s walk through some of the problems with that study and then look at several other studies that show a different outcome.
As noted in a review by Magnuson (http://bit.ly/2ejmBDD
), one of the aspects of most concern is that the authors assume that results based on saccharin alone may be extrapolated to all types of low calorie sweeteners. Only one of the tests reported included aspartame in a tabletop form (which meant other ingredients also were present; i.e., it was not a pure form of aspartame), and these were in doses several times that of typical human consumption.
Second, the Suez study was done in mice and those studies give indications related to human outcomes but they require human studies to confirm the outcome. While Suez did a follow-up in humans they did not measure the gut microbiota after consumption of two of the three low calorie sweeteners so the impact was not demonstrated.
Third, the three sweeteners consumed were given in dosages that were totally out of the realm of normal intake. Since the Suez study there have been at least 8 studies that have looked at this question, and the results are varied but one common outcome is that more human studies are needed. In the case of aspartame, a study by Daly et al. questioned how any effect would be possible since aspartame is completely digested in the small intestine to the two amino acids, phenylalanine and aspartic acid. As a result, it would never reach the microbiota and therefore it could not have the outcomes indicated. 2
Fourth, the study did not measure blood sugar levels consistently, so sometimes it was morning, sometimes it was after liquid intake, sometimes it was after solid food and they did not have a baseline measurement to which they could compare these readings. And last, the food records were for 3 days out of an 11 week study so comparing outcomes to intake is significantly lacking.
A study by Nettleton et al concludes that since the studies done thus far look at different microbes there is no consensus related to type of sweetener, microbes involved or individual microbiota variations. Thus concluding that low calorie sweeteners change or impact the gut microbiome is not supported by evidence.3 Finally, a small pilot study in humans, conducted by Frankenfeld et al, found that there were no observable differences in the microbiome of those who consumed aspartame or acesulfame-K and those who did not consume these sweeteners.4
What these studies, and the others that I have not commented on, show us is that there is not a body of evidence that demonstrates that sweeteners impact the microbiome. As a Registered Dietitian what I can say, and do recommend, is that using low calorie sweeteners, as a part of an overall healthful eating plan, provides an opportunity to enjoy a sweet taste without having to turn to caloric sweeteners. Stay tuned for more research!
- Jotham Suez , Tal Korem, David Zeevi, Gili Zilberman-Schapira, Christoph A. Thaiss , Ori Maza , David Israeli , Niv Zmora, Shlomit Gilad , Adina Weinberger, Yael Kuperman, Alon Harmelin, Ilana Kolodkin-Gal, Hagit Shapiro, Zamir Halpern, Eran Segal & Eran Elinav. Artificial sweeteners induce glucose intolerance by altering the gut microbiota. Nature 2014 Oct 9;514(7521):181-6
- Kristian Daly, Alistair Darby, Soraya Shirazi-Beechey. Low calorie sweeteners and gut microbiota. Physiol Behav (2016)
- Jodi Nettleton, Raylene Reimer, Jane Shearer. Reshaping the gut microbiota: Impact of Low Calorie Sweeteners and the Link to Insulin Resistance? Physiol Behav (2016)
- Cara Frankenfeld, Masoumeh Sikaroodi, Evan Lamb, Sarah Shoemaker, Patrick Gillevet. High-Intensity sweetener consumption and gut microbiome content and predicted gene function in a cross-sectional study of adults in the United States. Annals of Epidemiology 25 (2015 736- 742)
Connie Diekman, MEd, RD, CSSD, LD, FAND, is a nutrition communications consultant and Director of University Nutrition at Washington University in St. Louis, Missouri. She regularly provides expert counsel to the Aspartame Resource Center.