Sweeteners and the Gut Microbiome
Sweeteners have been gaining a lot of popularity in the diet industry for the last decade. With sweeteners, food can be made to taste sweet, without having to add sugar to it. This results in a low calorie or ‘light’ product of which people thought for a long time that it could help you lose weight. But is that actually true? How healthy are sweeteners and how do they affect the gut microbiome?
What are Sweeteners?
Sweeteners are widely used in many products nowadays. They can either be Non-Nutritive Sweeteners that have a high sweetening intensity and low calorie content or Low-Calorie Sweeteners which are slightly sweeter than sugar but contain fewer calories.
The sweeteners taste way sweeter than sugar does, without the calories that sugar has. This has made it a popular product in the food industry to flavor factory-made products. Sometimes you really have to dive into the tiny letters of an ingredients list to find out if a product contains sweeteners. It is often added to many products that are not even labeled as ‘light’ products.
Non-nutritive Sweeteners are either factory-made or chemically derived from plants. Low-Calorie Sweeteners are polyols or sugar alcohols that are poorly digested in the intestines, so they don’t provide many calories.
Many people know sweeteners as a white powder, a white tablet, or as a watery fluid.
The sweeteners that are used in food have been deemed safe by food authorities. But lately, more and more studies show up that doubt that in relation to diabetes, metabolic syndrome, and the gut microbiome.
Today we’ll be focusing on the gut microbiome and what is actually known and proven to be true in humans.
Sweeteners and the Gut Microbiome
A lot of the effects of sweeteners on the gut microbiome have been a subject of speculation and animal studies. As a result, more and more studies on humans are being done, in order to provide a clear answer.
In the last couple of years, I have seen studies come by on the subject on multiple occasions, mentioning the increased chance of dysbiosis in the gut microbiome. But as I dove into it to write this blog, most of those studies turned out to be test-tube and mice studies. And the studies done on humans mostly showed an effect on diabetes or metabolic syndrome, not the gut microbiome (yet).
Although those test-tube and mice studies can give an indication of an effect, you can’t translate those studies to humans, and so more research is needed. As you may know, studies take a long time to do, so much of the effects will still be unknown.
For now, I will shine a light on the sweeteners that have shown an effect on the human gut microbiome and what that effect was.
A little sidenote to begin with. Even though human studies are not yet here in regards to the microbiome, I still wouldn’t recommend using artificial sweeteners. There is stronger evidence on the effect of sweeteners on diabetes, non-alcoholic fatty liver disease and metabolic syndrome in humans. And there are mice studies that don’t paint a positive picture regarding the sweeteners. Try to consume natural foods and if you do have a sweet tooth, look for (dried) fruit or honey/agave syrup (in small amounts).
Aspartame is often used in soda and drinks to sweeten it. According to a large review study from 2020, aspartame is completely absorbed in the small intestine and never arrives in the large intestine. So it wouldn’t have an effect on the microbiome, because it never comes into contact with it.
Acesulfame-K is mostly absorbed in the small intestine, and less than 1% of the acesulfame-K we consume reaches the large intestine. In mice, some studies have shown a change in the microbiota and production of short-chain fatty acids. Although most of these studies have been done with large amounts of acesulfame-K.
Cyclamate is eliminated through feces and can have an effect on the gut microbiome. One study that used a machine that mimics the human digestive tract and used human stool samples showed that cyclamate reduces the production of Short Chain Fatty Acids like butyrate and propionate and showed an increase in the bifidobacteria.
Reduced amounts of Short Chain Fatty Acids have been liked to a higher incidence of Irritable Bowel Syndrome (IBS).
Sucralose is poorly digested and is mostly being excreted with the stools. In a small study, where they studied the stools of 13 healthy humans the ingestion of sucralose resulted in an abundance of the bacteria Escherichia, Shigella, and Bilophila.
Saccharin is absorbed for about 85% and doesn’t reach the large intestine. A study that used a machine to mimic the human digestive system showed a decrease of firmicutes and thus Short Chain Fatty Acids after consumption of saccharin.
Also known as stevia is not digested or absorbed in the upper digestive tract and reached the large intestine intact. A study that used a machine to mimic the human digestive system, showed possible effects of stevia on the gut microbiome. Reducing the amount of ammonia present and reducing bifidobacteria. It leads to a higher pH and increased production of short-chain fatty acids.
Polyols are a sweetener that is naturally present in many fruits and vegetables and are also part of the FODMAP diet.
The polyols can be recognized as sweeteners that have names ending in -ol. Like xylitol, mannitol, maltitol. And both the natural polyols and chemical polyols attract fluids into the intestine. Which can lead to diarrhea.
Polyols that are naturally occurring can definitely be healthy for your gut microbiome. They can lead to diarrhea and gas production, and if that is something you notice, it is smart to limit your intake of the polyols.
Erythritol is a polyol that is for 90% absorbed in the small intestine. The other 10% is being fermented by the gut microbiome, and this doesn’t seem to lead to gas production.
A test-tube study with the gut microbiome showed no effects of erythritol on the diversity and composition of the gut microbiome. It did seem to increase the production of healthy Short Chain Fatty Acids.
Isomalt is not absorbed in the small intestine and is fermented by the gut microbiota. From studies, it is expected that isomalt can function as a prebiotic that can contribute to a healthy environment in the large intestine with a high production of the Short-Chain Fatty Acid butyrate.
Lactitol is not absorbed in the small intestine and is fermented in the large intestine. With this fermentation gas and short-chain fatty acids are produced. Lactitol can also be seen as a prebiotic. It helps create a healthy environment in the large intestine by reducing the permeability of the gut lining and increasing the production of healthy bifidobacteria and lactobacilli.
Maltitol is hardly absorbed in the small intestine and is fermented in the large intestine. Only one study on humans has been done with maltitol and this showed an increase in bifidobacteria, lactobacilli, and short-chain fatty acids. More research is needed to be able to say anything about its effects.
Sorbitol is partially absorbed in the small intestine and the rest is fermented in the large intestine. Short-Chain Fatty Acids and gas are produced during the fermentation, and a higher intake of sorbitol generally leads to bloating and flatulence. The effect of sorbitol on the gut microbiome is not known yet.
Mannitol has an identical molecular formula to sorbitol. About 75% of the mannitol we consume reaches our large intestine. It has been shown to increase the production of the short-chain fatty acids butyrate and propionate in the large intestine. Not enough data is available to take conclusions out of this.
Xylitol is chemically derived from birch trees. It travels through the intestinal tract mainly unabsorbed and is fermented in the large intestine. During fermentation, a small amount of gases are produced and larger amounts of Short-Chain fatty acids. High intakes of xylitol lead to the attraction of fluids in the intestine and diarrhea.
As mentioned, there is limited scientific evidence on the effects of sweeteners on the human microbiome.
Multiple mice studies have shown that alterations in the gut microbiome are possible with artificial sweeteners. Polyols in general seem to have a more positive effect on the microbiome. Though they can lead to the production of gas and the attraction of fluids.
Sweeteners that are absorbed in the small intestine have shown to have effects on the onset of diabetes (insulin resistance), non-alcoholic fatty liver disease, inflammation, and metabolic syndrome. For me, reason enough to just stay away from them and get some sweetness out of natural sources if you need to!
Are you (still) using sweeteners? Or did you change your mind? Let me know in a comment below!
Hi there, I’m Manon.
In my daily life I work as a registered dietitian in the Netherlands with a special interest in gut health.
During my workday I get loads of questions about healthy food, recipes and lifestyle to make it a little easier to get healthy. On Positive Gut I collect my best recommendations, tips and recipes to make your healthy lifestyle a little easier!