Are Artificial Sweeteners Bad for You?

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In 1879, a chemist named Constantin Fahlberg sat down to dinner without washing his hands after a day spent handling coal tar. His bread tasted sweet. So he went back to the lab, started tasting everything on his bench until he found the source, and that is how the world got saccharin. The first artificial sweetener entered human history because a man would not wash his hands before dinner. Nearly 150 years later, we are still arguing about whether artificial sweeteners are quietly killing us.

This week, Zoë and Kylee Van Horn, RDN, take on the question every diet-soda drinker has had to defend at a gas station: are artificial sweeteners actually bad for you? The honest answer is that the fear has wildly outrun the science. The fuller answer runs through coal tar, Theodore Roosevelt, a Donald Rumsfeld cameo in the FDA approval process, and a hundred years of moral panic wearing a lab coat.

We sort out what these things actually are, from aspartame and sucralose to stevia, monk fruit, and the sugar alcohols hiding in your protein bar. We trace where the cancer fear came from (male rats, enormous doses, and a urinary quirk human bodies do not have) and why the WHO calling aspartame "possibly carcinogenic" lands it in the same hazard tier as pickled vegetables and working as a carpenter. We get into the genuinely fascinating part, the gut microbiome research where scientists grew human gut bacteria in mice, and the difference between "this molecule does something in a petri dish" and "this is doing something to you." And we cover the one category that actually earns an athlete's attention: sugar alcohols, and what they can do to a long run.

We also name the diet culture of it all. These products were sold to women as permission and restriction in the same bottle, and that baggage still shapes how a lot of us feel about a can of Diet Coke.

Bottom line: at realistic doses there is no meaningful cancer signal for any approved sweetener. The microbiome science is real but unfinished. Sugar alcohols are the only group that warrant real caution, mostly for your gut, and mostly if you train hard. You are allowed to drink the diet soda. And if you can recite your daily sucralose intake from memory, the thing worth examining probably is not the sucralose.

Episode Chapters

00:00Cold open: do you have a diet soda thing?

06:13What actually counts as an artificial sweetener

11:45A brief, unhygienic history of sweeteners

22:05The every-15-years villain cycle

25:04Do artificial sweeteners cause cancer?

35:26The gut microbiome and the Suez mouse study

40:03Stevia, antimicrobials, and the petri-dish problem

45:41How sweeteners actually work (and sugar alcohols)

50:29Erythritol and the heart-attack headline

54:32The diet culture of it all

55:37Does diet soda make you hungrier?

57:39Can tasting sweet spike your insulin?

59:32Where it fits, clinically and for athletes

1:05:36Practical takeaways

1:07:03Hot takes: artificial sweetener edition

Topics Covered

• Do artificial sweeteners cause cancer, and what the IARC Group 2B classification of aspartame actually means
• The saccharin bladder-cancer scare, the male-rat mechanism, and why it does not translate to human biology
• Sucralose and the in vitro DNA-damage studies (and why a petri dish is not a person)
• Artificial sweeteners and the gut microbiome: the Suez 2022 personalized glycemic-response study and the germ-free mice
• Stevia, monk fruit, and antimicrobial activity in the lab versus the living gut
• Sugar alcohols (erythritol, xylitol, sorbitol), the osmotic effect, and GI distress for athletes
• Erythritol and cardiovascular event risk: what the Cleveland Clinic study did and did not show
• The compensation hypothesis: does diet soda make you hungrier?
• The cephalic phase insulin response and whether tasting sweet matters metabolically
• Artificial sweeteners in electrolyte mixes, gels, and protein powders, and palate fatigue on long efforts
• The diet culture history of non-nutritive sweeteners as tools of restriction

Studies & References

• International Agency for Research on Cancer. (2023). Aspartame hazard and risk assessment results released [News release]. World Health Organization.
• McGlynn, N. D., Khan, T. A., Wang, L., Zibdeh, N., Widmer, R. J., Chiavaroli, L., ... Sievenpiper, J. L. (2022). Association of low- and no-calorie sweetened beverages as a replacement for sugar-sweetened beverages with body weight and cardiometabolic risk: A systematic review and meta-analysis. JAMA Network Open, 5(3), e222092. https://doi.org/10.1001/jamanetworkopen.2022.2092
• Suez, J., Korem, T., Zeevi, D., Zilberman-Schapira, G., Thaiss, C. A., Maza, O., ... Elinav, E. (2014). Artificial sweeteners induce glucose intolerance by altering the gut microbiota. Nature, 514(7521), 181–186. https://doi.org/10.1038/nature13793
• Suez, J., Cohen, Y., Valdés-Mas, R., Mor, U., Dori-Bachash, M., Federici, S., ... Elinav, E. (2022). Personalized microbiome-driven effects of non-nutritive sweeteners on human glucose tolerance. Cell, 185(18), 3307–3328. https://doi.org/10.1016/j.cell.2022.07.016
• Witkowski, M., Nemet, I., Alamri, H., Wilcox, J., Gupta, N., Nimer, N., ... Hazen, S. L. (2023). The artificial sweetener erythritol and cardiovascular event risk. Nature Medicine, 29(3), 710–718. https://doi.org/10.1038/s41591-023-02223-9
• World Health Organization. (2023). Use of non-sugar sweeteners: WHO guideline. World Health Organization.

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