Another Garbage Study Says Diet Soda is Bad For You

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If you watch my Twitch streams, you may know that I am a fan of caffeinated, carbonated, sugar-free beverages. They power my video game murder. And I’ve always looked out for the absolute least natural option available — a lot of people are very worried about “artificial” ingredients in things but I’m the opposite. I want everything in my afternoon beverage to be crafted by scientists in a laboratory. Diet Coke? Fine. Coke Zero, using a newly discovered sweetener (well, in 1967)? Great. Cherry Coke Zero? Now we’re talking. Dr. Pepper Zero Sugar with Cream Soda? FUCK YEAH. What is this? There is no natural flavor on Earth that is detectable in this beverage. The good lord god could NEVER. I love it.

And why am I not worried about putting this manmade can of chemicals in my precious temple of a body? Well, that’s because study after study has shown that it’s perfectly safe. In fact, the FDA points out that “Aspartame is one of the most exhaustively studied substances in the human food supply, with more than 100 studies supporting its safety.” It has no calories, it’s safe, and it’s delicious.

Meanwhile, consuming too much of the all-natural, blessed by god sweetener, sugar, leads to a cornucopia of disease: According to  Dr. Frank Hu, professor of nutrition at the Harvard T.H. Chan School of Public Health who published a 15-year study on the topic, “The effects of added sugar intake — higher blood pressure, inflammation, weight gain, diabetes, and fatty liver disease — are all linked to an increased risk for heart attack and stroke.” Mmm, sweet, delicious, all-natural stroke.

Despite this, the general public will simply never stop doing two things: consuming WAY more processed sugar than is healthy, and suspiciously questioning artificial sweeteners. Which brings me to today’s topic: “Artificial sweeteners can turn healthy gut bacteria into pathogens — Sugar substitutes could cause harmful bacteria to invade the intestine, which can potentially lead to life-threatening infections.” Oh nooooo!

“Artificial sweeteners can potentially turn healthy bacteria in the gut microbiome into harmful microbes and potentially cause serious health issues such as blood poisoning, scientists have said.

UK researchers have found that sugar substitutes such as saccharin, sucralose, and aspartame – found in soft drinks and processed foods – can cause beneficial bacteria in the intestines such as E. coli (Escherichia coli) and E. faecalis (Enterococcus faecalis) to become pathogenic, or disease causing.”

“Pathogenic bacteria can invade and kill Caco-2 cells – cells which line the wall of the intestine. The researchers found that an amount of sweeteners equivalent to two cans of diet soft drink can significantly increase the ability of E. coli and E. faecalis to attach to Caco-2 cells.”

Holy crap! Two cans of diet soft drink is exactly the number of cans of diet soft drink I drink EVERY DAY! I’M GONNA DIE OF SEPSIS!

Okay, the important news up front: I’m not gonna die of sepsis. I’m probably going to die of skateboarding because I keep doing it even though I’m terrible at it and I’m 40 years old. This study does not actually back up any of the scary claims in the article. Let’s get into it.

The big news up front: this study did not examine humans. In fact, it didn’t examine any living animal at all. All the work was done in vitro, meaning a petri dish, or perhaps a test tube.

This is very important because, well, the human body is not a test tube. We have a complex system of checks and balances, and so it’s much easier to make something happen in a laboratory dish than in a body. Here’s an example: the researchers looked at Caco-2 cells that come from the large intestine. They put three artificial sweeteners — aspartame, saccharin, and sucralose — directly into those cells, and found that yep, they increased the production of biofilms, potentially dangerous clusters of bacteria.

That WOULD be bad, if aspartame ever even made it to the large intestine, where Caco-2 cells are found, but it doesn’t. As summarized by the European Food Safety Authority, “Aspartame is fully broken down in our gut to aspartic acid and phenylalanine, which are absorbed and enter our body. In addition, the methyl group from the modified phenylalanine is released in the gut to

form methanol. Methanol is also absorbed by the body and most of it used to produce energy.

“All the scientific studies to date in animals and human volunteers have shown that the breakdown of aspartame in the gut is very rapid and complete. No aspartame has ever been found in the blood or any organ after ingestion.” 

ANY organ. Including the large intestine. These researchers put aspartame on cells that are physically incapable of ever seeing a single drop of aspartame. As for saccharin and sucralose, they may be able to make it to the large intestine but in extremely tiny amounts. Other research has shown you need to consume massive amounts of them to affect your gut microbes.

So right there, we can say that this study is garbage. Drinking two cans of soda with any of those sweeteners will not affect your cells the way that the cells in this study were affected, because two cans’ worth of sweeteners will never come into contact with those cells. And in they case of aspartame, the most common sweetener used in these sodas, a hundred cans of soda won’t ever hit those cells. You could do Coke Zero keg stands all day long and not a single molecule of aspartame will ever shake hands with the Caco-2 cells in your large intestine.

So yeah, that would be enough to let you know that you shouldn’t pay attention to this study, but just for fun here’s one more reason: there was no real control.

Well, they did have one control: in addition to E. coli and E. faecalis, they also tested the sweeteners on Staphylococcus, a bacteria that is not found in the gut. Now, I’m no scientist but when I read quotes from a study author like “We know that overconsumption of sugar is a major factor in the development of conditions such as obesity and diabetes. Therefore, it is important that we increase our knowledge of sweeteners versus sugars in the diet to better understand the impact on our health,” *I* would assume that the control they were using to compare would be, uh, you know, SUGAR. Sugar! If you want to “better understand” sweeteners versus sugars maybe you should compare those two things IN YOUR STUDY! Just saying!

And then, I don’t know, just for fun, maybe throw in a few other sugar substitutes that scientists have already found can reach the large intestine in decent amounts, like isomalt, maltitol, lactitol, and xylitol, instead of aspartame. And for god’s sake, study them in the actual amounts thought to be able to make it to the large intestine, not the entire amount found in two cans of soda. 

They didn’t do any of that, and they still got published. How? Well, this paper was published in the International Journal of Molecular Sciences, a product of Multidisciplinary Digital Publishing Institute (MDPI), a “predatory/questionable publisher” that has a “mission to earn as much money as possible through article submissions” leading them to “regularly accept questionable papers,” and they are “known for aggressively spamming academics to edit special issues, often in fields that are far away from the expertise of the recipient of the frequent and insisting emails.” They boast of an extremely fast turnaround time of 20 days from paper submission to first decision, and an analysis run by Paolo Crosetto, Director of Research at France’s Institut national de la recherche agronomique, found that it was only 25 days between submission and acceptance, including revisions — way too short of a time to allow for proper vetting.

A classic story: researchers with a crappy, inconclusive study pay big bucks so a predatory journal publishes them, and then a press release gets picked up by “science” news outlets like EurekAlert and ScienceFocus. Soon it will leak onto Facebook, my mom will see it, and I will once again be shamed for bringing that dangerous Coke Zero into her house the next time I visit. And that’s how your bad science sausage gets made.

Rebecca Watson

Rebecca is a writer, speaker, YouTube personality, and unrepentant science nerd. In addition to founding and continuing to run Skepchick, she hosts Quiz-o-Tron, a monthly science-themed quiz show and podcast that pits comedians against nerds. There is an asteroid named in her honor. Twitter @rebeccawatson Mastodon Instagram @actuallyrebeccawatson TikTok @actuallyrebeccawatson YouTube @rebeccawatson BlueSky

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