Flashback Friday: Effect of Sucralose (Splenda) on the Microbiome

On April Fool’s Day, 1998, the FDA approved the artificial sweetener sucralose, aka one-six-dichloro-one-six-di-deoxy-beta-D-fructo-furanosyl-four-chloro-four-deoxy-alpha-D-galacto-pyranoside, but despite its scary name, the worst it seemed to do was just be a rare migraine trigger in susceptible individuals. To which the manufacturer of sucralose replied that you have to weigh whatever risk there may be against its broader health benefits, helping to mitigate the health risks associated with our national epidemic of obesity.

That’s what the hope was, to provide a healthy sugar substitute to provide a sweet taste without the calories or spikes in blood sugar. However, that’s not how it appears to have turned out, with population studies tying consumption of artificial sweeteners, mainly in diet sodas, with increased risk of developing obesity, metabolic syndrome, and type 2 diabetes. But an association is not causation. You’ve got to put it to the test. If you give obese individuals the amount of sucralose found in like a can of diet soda, they get a significantly higher blood sugar spike in response to a sugar challenge, requiring significantly more insulin – 20% higher insulin levels in the blood – suggesting sucralose causes insulin resistance, potentially helping to explain the links between artificial sweetener consumption and the development of diabetes, heart disease, and stroke. So, sucralose is not like some inert substance, but affects the blood sugar response. But how?

The Splenda company emphasizes that sucralose is hardly even absorbed into the body and, so, stays in the digestive tract to be quickly eliminated from the body. But the fact that it’s not absorbed in the small intestine means it makes it down to the large intestine and may affect our gut flora. There had been studies done on artificial sweeteners and the gut bacteria of rats going back years, but there had never been any human studies… until now. They tested saccharin, sucralose, and aspartame, the artificial sweeteners in Sweet & Low, Splenda, and NutraSweet, and found that non-caloric artificial sweeteners induce glucose intolerance by altering the microbes in the gut. The human studies were limited, but after a few days on saccharin, for example, some people got exaggerated blood sugar responses tied to changes over just one week to the type of bacteria they had in their gut.

Acesulfame K, another common artificial sweetener, was also found subsequently to be associated with changes in gut bacteria. So, all this time, artificial sweeteners were meant to stave off chronic diseases but may actually have been contributing to the problem due to microbial alterations. Some in the scientific community were surprised that even minor concentrations of a sweetener—they’re talking about aspartame here—are sufficient to cause substantial changes in gut inhabitants. Others were less surprised. Each molecule of aspartame is metabolized into formaldehyde. That may be why some people who are allergic to formaldehyde have such bad reactions to the stuff. Therefore, it’s not unexpected that even small amounts might modify bacterial communities.  There are mixed reports about the safety of aspartame. All of the studies funded by the industry vouch for its safety, whereas 90% of independently funded studies report that aspartame can cause adverse health effects. That should tell you something.

Undoubtedly, consumers of these food additives, which are otherwise perceived as safe, are unaware that these substances may influence their gut bacteria. This may be of particular importance to patients with diseases correlated with modifications of the gut bacteria, such as inflammatory bowel diseases, like ulcerative colitis and Crohn’s disease. These individuals may not realize artificial sweeteners may be affecting their gut. Might the effect be large enough to actually cause changes in the incidence of inflammatory bowel disease? Canada was the first country to approve the use of sucralose—what happened to their rates of IBD? Rates did seem to double after the approval of sucralose. What about in the United States? After decades of stable rates of ulcerative colitis and Crohn’s disease, rates started to go up. In China, after the approval of sucralose, IBD rates rose 12-fold. Again, these could just be total flukes, but such correlations were also found on two other continents as well.  The more graphs that you see like this, the harder it is to dismiss a possible connection.

The good news, though, is that after stopping artificial sweeteners, the original balance of gut bacteria may be restored within weeks. Now, of course, the negative consequences of artificial sweeteners should not be interpreted to suggest that we should all go back to sugar and high fructose corn syrup. For optimal health, it is recommended that we all try to cut down on both.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.

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Images thanks to Dave Crosby via Flickr.