So Do I Have To Stop Drinking Diet Coke Now, Or What?

Experts reveal their thoughts in light of the aspartame news.

Experts weigh in: Is Diet Coke worse than regular Coke?
Caroline Wurtzel/Bustle; Getty Images

For Diet Coke drinkers, it’s impossible to deny the allure of the caffeinated, carbonated beverage. Sure, Coca-Cola, the classic, has been an A-list soda for decades, but the Coke alternative has had massive appeal since it was introduced in 1982. Kate Moss is now the drink’s creative director (again), for crying out loud. It’s probably all due to its seemingly magical nutritional properties: Namely, it seems healthier because it contains zero calories and zero sugar, yet still tastes just as damn good as a regular Coke. And that’s thanks to a little ingredient called aspartame.

Aspartame is a nonnutritive sweetener that’s responsible for how delicious Diet Coke and about a zillion other foods and beverages are, and it’s been around since it was FDA approved in 1981. Besides our darling DC, it’s found in things like Gatorade Zero, sugar-free gum, sugar-free syrups, and practically anything that tastes sweet but doesn’t have any caloric or glucose-spiking ramifications for being so. This seems great in theory, but aspartame doesn’t come without its own host of adverse effects.

The dark side of aspartame is nothing new: Studies investigating negative health claims on the nonnutritive sweetener began popping up in 1984, but the Food and Drug Administration (FDA), Centers for Disease Control (CDC), and European Food Safety Authority’s Panel on Food Additives and Nutrient Sources Added to Food (ANS) all wound up reconfirming its safety in the ’90s and 2000s despite its anecdotal links to multiple sclerosis, headaches, and GI issues and research-backed links to mood changes and depression. But it made headlines last month — and scared DC stans everywhere — when the World Health Organization (WHO) officially declared aspartame as “a possible carcinogen for humans.”

In light of this news, Diet Coke girlies are asking: Should we just drink regular Coke, then? Here’s an investigation into the all-important question regarding everyone’s favorite afternoon treat.

What Is Aspartame, Anyways?

Aspartame is a sugar substitute that’s 100 times sweeter than regular sugar. Since it packs such a major punch, it’s used in very small doses to sweeten certain foods, drinks, chewing gum, and cough drops, says Dr. Ernst von Schwarz, M.D., a triple board-certified clinical and academic cardiologist.

Specifically, aspartame is made from a peptide bond. “It comes from taking a piece of protein and connecting it with an ester polypeptide [a bioactive compound], which makes it noncaloric,” says Melanie G. Murphy Richter, MS, RDN, a registered dietitian.

It’s the second nonnutritive sweetener that hit the market, the OG being saccharin. “When saccharin came out in the early 1900s, people thought it was amazing, so they began looking into ways to offshoot what was so great about it,” says Murphy Richter. “Aspartame was the next iteration of that.”

What Does Aspartame Do To Your Body?

Since it’s sweet without being real sugar, aspartame doesn’t spike your glucose levels — which seems good until you realize what else it does to your body. “It’s going to cause a downstream effect of glucose dysregulation on your mouth, taste buds, and gut,” says Murphy Richter. Essentially, the more that you eat something that is super sweet, the more your taste buds crave something that sweet instead of the flavors found in foods that are really good for you.

While diet drinks are widely believed to aid in weight loss or weight maintenance, von Schwarz says several studies have found this theory to be “complete nonsense.” He says, “From my own experience — especially in patients with heart disease — aspartame and other sugar substitutes actually create a sugar craving.” And though it doesn’t spike your glucose levels, von Schwarz says aspartame produces a negative feedback in the pancreas, which produces insulin. “So since the sugar levels are not going significantly up, it tells the body that you need more sugar,” he says.

What’s more, nonnutritive sweeteners are not all that great for your gut. “They’re well-known to cultivate an environment in your gut that preferentially allows certain types of bacterium to grow that are more pathogenic,” says Murphy Richter. “Sugar does in general too, but nonnutritive sweeteners have a more varied effect — which is a problem because your gut determines how well your immunity functions, how well you create hormones and neurotransmitters, your circadian rhythm, and your ability to sleep well.” But it’s not like sugar is all that harmless in comparison.

Nonnutritive Sweeteners Vs. Sugar

Though sugar may start to sound like the sweeter choice, note that it’s still a villain for your diet in its own right. Von Schwarz says it poses one of the biggest health risks because of everything it does to the body. “Sugar itself is pro-inflammatory, leads to diabetes, leads to metabolic syndrome, and leads to chronic inflammation from the teeth to your blood vessels, the heart, and the brain,” he says. “And we all have way too high consumption of it on a daily basis.”

It may not be carcinogenic, but it leads to the development of cardiovascular disease — and von Schwarz points out that more people die of cardiovascular disease than all cancers combined. A large contributor to heart disease, BTW, is obesity and diabetes. Hence why we have such a demand for low-calorie products and nonnutritive sweeteners, according to Murphy Richter.

Then the carcinogenic risk comes into play if you’re going the aspartame route. To put things into perspective, though: What isn’t dangerous these days? “There is a possible cancer risk with aspartame, just as there is for many other components of our daily life,” says von Schwarz. For instance, cellphone use and talc are also classified as potential carcinogens.

The Verdict

So, which soda should you drink then? Sorry DC drinkers, but both von Schwarz and Murphy Richter would go with a Coke — but not because of aspartame’s potential link to cancer. Back to that point: The carcinogenic risk, according to the WHO, comes if you’re consuming 40 milligrams per kilogram of body weight a day. Translation? “That equals between 15 and 22 cans of Diet Coke — or diet soda or other products that contain aspartame — every day,” says von Schwarz. “That’s usually not reached anyhow by any individual.”

He wouldn’t touch a Diet Coke because of its domino effect that could lead to cardiovascular disease. Thus, he’d recommend going with Coke if you want something sweet. “I wouldn’t recommend that every day, but maybe once or twice a week,” he says. And Murphy Richter would choose Coke in light of aspartame’s long list of effects on your body, especially your gut. That said, Diet Coke would be a better choice for those who have diabetes since sugar would affect their insulin levels.

After all that’s been said, note that Diet Coke is still approved for human consumption, after all, so what you reach for is your prerogative. In an ideal world, of course, you’re not drinking soda at all. But I’m not here to stop you from having a good time.

Studies referenced:

Azeez, O. H. (2019). Long-Term Saccharin Consumption and Increased Risk of Obesity, Diabetes, Hepatic Dysfunction, and Renal Impairment in Rats. Medicina, 55(10). https://doi.org/10.3390/medicina55100681

Basu, S. (2012). The Relationship of Sugar to Population-Level Diabetes Prevalence: An Econometric Analysis of Repeated Cross-Sectional Data. PLoS ONE, 8(2). https://doi.org/10.1371/journal.pone.0057873

Czarnecka, K. (2021). Aspartame—True or False? Narrative Review of Safety Analysis of General Use in Products. Nutrients, 13(6). https://doi.org/10.3390/nu13061957

Della Corte, K. W. (2018). Effect of Dietary Sugar Intake on Biomarkers of Subclinical Inflammation: A Systematic Review and Meta-Analysis of Intervention Studies. Nutrients, 10(5). https://doi.org/10.3390/nu10050606

Lindseth, GN. (2014). Neurobehavioral effects of aspartame consumption. Res Nurs Health. 2014 Jun;37(3):185-93. doi: 10.1002/nur.21595. Epub 2014 Apr 3. PMID: 24700203; PMCID: PMC5617129.

Ma, X. (2021). Excessive intake of sugar: An accomplice of inflammation. Frontiers in Immunology, 13. https://doi.org/10.3389/fimmu.2022.988481

Mathur, K. (2020). Effect of artificial sweeteners on insulin resistance among type-2 diabetes mellitus patients. Journal of Family Medicine and Primary Care, 9(1), 69-71. https://doi.org/10.4103/jfmpc.jfmpc_329_19

Pang, M. D. (2019). The Impact of Artificial Sweeteners on Body Weight Control and Glucose Homeostasis. Frontiers in Nutrition, 7. https://doi.org/10.3389/fnut.2020.598340

Ruiz-Ojeda, F. J. (2019). Effects of Sweeteners on the Gut Microbiota: A Review of Experimental Studies and Clinical Trials. Advances in Nutrition, 10(Suppl 1), S31. https://doi.org/10.1093/advances/nmy037

Seo, E. H. (2019). Association between Total Sugar Intake and Metabolic Syndrome in Middle-Aged Korean Men and Women. Nutrients, 11(9). https://doi.org/10.3390/nu11092042

Shil, A. (2021). Artificial Sweeteners Negatively Regulate Pathogenic Characteristics of Two Model Gut Bacteria, E. coli and E. faecalis. International Journal of Molecular Sciences, 22(10). https://doi.org/10.3390/ijms22105228


Dr. Ernst von Schwarz, M.D., triple board-certified clinical and academic cardiologist

Melanie G. Murphy Richter, MS, RDN, registered dietitian