How Does Diet Soda Affect Your Gut?
Keep an open mind over this controversial health topic.
It seems nothing has become more controversial in the health and wellness space than diet soda and artificial sweeteners. If you talk to fitness people, they will say: “Oh, they’re fine as long as you’re still eating in a calorie deficit.” Then if you talk to some natural health professionals, they’ll say: “Oh, as long as you stick to things with stevia, you’ll be fine.” Even some health gurus say, "Don’t consume any of those because it will wreck your gut!”
Does your favorite diet soda, protein bar, or Splenda you add to your morning coffee really “wreck your gut?” Can they still be enjoyed without worrying about messing up your gut microbiome? If you’re someone who gets bloated and gassy whenever you have your favorite low-calorie ice cream, why is that? Can you ever reach a point where you can include them symptom-free?
Defining the Terms
We think of artificial sweeteners as part of a larger umbrella term called non-nutritive sweeteners (NNS), aka they provide little to no calories. They are generally sweeter and have lower calorie content per serving than sweeteners with calories such as sucrose — table sugar — or corn syrup. NNSs are then divided into artificial sweeteners — Sweet’n Low, Splenda — and natural sweeteners — stevia and monk fruit. Then we have low-calorie sweeteners, such as sugar alcohols — Erythritol and sorbitol —generally less sweet than table sugar (1).
Safety Profile
The European Union, along with the FDA-equivalent in Europe — European Food Safety Authority — evaluated and confirmed that the above-mentioned sweeteners
“are safe for human consumption and do not cause cancer or other health-related problems as long as they are consumed within the Acceptable Daily Intake (ADI)” (1).
Two things here: 1) Your logical next question is likely, ‘What’s the ADI?’ 2) People love to talk about how Europe has better rules and regulations regarding food products, so the fact they consider sweeteners safe says a lot.
Saccharin’s — sweetener in Sweet’N Low — ADI is equivalent to 45 packets, aspartame — in Splenda — is 75 packets, stevia is 9 packets, and there is no specified limit for Monk Fruit (2). Good luck eating 45–75 packets simultaneously without feeling palate fatigue! Interesting to note that stevia, often beloved because of its natural origin, has a lower ADI than its artificial counterparts.
Diet Coke vs. Zevia
Many diet sodas are sweetened with aspartame. Aspartame has been one of the more heavily debated sweeteners for its effects on health. Up to 2022, we had no evidence that it changed the gut microbiome in humans (1). However, in 2022 a pretty impactful study found that aspartame can alter the microbiome. Specifically, it increased the abundance of B.fragilis in the gut (3). What does that actually mean?
We have no idea. B.fragilis is a normal resident of the human gut, and some positive health practices are associated with changes in this species. This speaks to the idea that we don’t know what a “healthy” gut microbiome looks like.
Aspartame is metabolized — broken down — into more minor chemical compounds and fully absorbed before reaching the large intestine. That’s the stick; if something is going to influence our gut microbiome, it would have to reach the large intestine, as most of our bacteria live there.
Zevia — my personal favorite diet drink — is sweetened with stevia. Stevia, in all its natural glory, may affect our gut bacteria. Bacteroides are one of the dominant phyla — major kingdoms of bacteria — in our gut (B.fragilis falls under the phyla of Bacteroides)(4). These types of bacteria have the ability to break down stevia and use its by-products as a fuel source (1). If they can use it for fuel, there’s a theoretical chance consuming more stevia could favor their growth. However, just because something alters the microbiome doesn’t mean that thing — stevia — is good or bad.
You know what they say: “Everything in moderation, including moderation.” If substituting regular soda for diet soda helps you reduce your calorie intake and lose weight, don’t let these studies scare you. If your goal is general health, and you only consume diet soda a few times a month, I wouldn’t worry about it. If you’re consuming them a couple of times a week, I wouldn’t even worry. Now, a couple of times a day, every day, I’d start to think about it. We just don’t have enough data on the long-term effects of diet soda consumption and changes in gut bacteria. I like to err on the side of caution.
Quest Bars & Halo Top
If you’ve been in the fitness and nutrition community for a while, these two foods likely hold a special place in your heart…and your gut. Often touted for their high fiber, high protein, and lower calorie content, they’re rich in polyols. They aren’t completely inert. In those with IBS or FODMAP sensitivities, they can cause some digestive mayhem. Polyols — sugar alcohols — consist of Erythritol, common in Quest Bars & Halo Top, maltitol in ONE Brands protein bars, and sorbitol in 1st Phorm Level-1 Bars. All these bars taste great going down, but all the bloating and gas I feel after eating them makes me question my decisions. Don’t think I’ll be sponsored by these companies anytime soon.
What happens when we ingest these sugar alcohols? For some, diarrhea and gas ensue when they overindulge in them, particularly for those with IBS. Specifically, Erythritol gets mostly absorbed in the small intestine and excreted in our urine, seemingly having no effect on our gut microbiome (1). Maltitol does not get absorbed by the small intestine, thus making its way into the large intestine, where it can undergo fermentation by our gut bugs. Since it undergoes fermentation, it could theoretically influence our microbiome; however, there isn’t much evidence to support that (1). Lastly, sorbitol seems to be mostly malabsorbed and can even cause digestive discomfort in some healthy people (1). Sorbitol also seems to affect those with IBS more than others. However, no information has come out about its influence on the microbiome.
What does all this mean? It suggests Erythritol is fairly benign, especially if you only consume 1 bar/day. This feels like a win for Halo Top and Quest Bars, but there’s still other ingredients — insoluble corn fiber, Chicory Root Fiber, Ultrafiltered skim milk — that can cause digestive symptoms. Pay more attention to foods with maltitol and sorbitol, especially if you have IBS or frequent digestive discomfort.
In my opinion, I don’t think diet sodas and sweeteners are the demons like a lot of health gurus claim. In moderation, they can be added to a well-balanced diet. They can help satisfy that sweet tooth you’re looking for without packing on the calories. However, moderation could simply mean one sip if you’re dealing with underlying gut issues. Once you work on optimizing your gut’s function, you’ll hopefully be able to broaden your diet.
If you’re looking for help with your gut issues, I highly encourage you to seek a Functional Medicine Practitioner with experience in the “gut health” realm.
As always, Trust in, Your Gut.
Disclaimer: The contents of this article are for educational purposes only and are not intended to diagnose or treat any condition. Do not apply any of the information in this article without first speaking with your doctor.
Text-Reference
- Ruiz-Ojeda FJ, Plaza-Díaz J, Sáez-Lara MJ, Gil A. Effects of Sweeteners on the Gut Microbiota: A Review of Experimental Studies and Clinical Trials [published correction appears in Adv Nutr. 2020 Mar 1;11(2):468]. Adv Nutr. 2019;10(suppl_1):S31-S48. doi:10.1093/advances/nmy037
- FDA. Additional Information about High-Intensity Sweeteners Permitted for Use in Food in the United States. 2014. Available from omhttps://www.fda.gov/food/food-additives-petitions/additional-information-about-high-intensity-sweeteners-permitted-use-food-united-stat, Accessed 2021.
- Suez J, Cohen Y, Valdés-Mas R, et al. Personalized microbiome-driven effects of non-nutritive sweeteners on human glucose tolerance. Cell. 2022;185(18):3307–3328.e19. doi:10.1016/j.cell.2022.07.016
- Rinninella E, Raoul P, Cintoni M, et al. What is the Healthy Gut Microbiota Composition? A Changing Ecosystem across Age, Environment, Diet, and Diseases. Microorganisms. 2019;7(1):14. Published 2019 Jan 10. doi:10.3390/microorganisms7010014
