Well, it’s a day ending in “y” so it must be time for another study to grab mainstream media headlines proclaiming that something you love causes cancer. Let’s spin the wheel and see what it will be! Hmm, looks like the wheel has stopped on ARTIFICIAL SWEETENERS! Sorry, cell phones, maybe next time.
If you’re seeing a lot of news stories popping up about your Diet Coke killing you, the culprit is a new study out of France, where researchers combed through ten years of existing data to conclude that “artificial sweeteners (especially aspartame and acesulfame-K)…were associated with increased cancer risk.”
Here are the facts up front: first and foremost, this is a correlation, not causation. They did not find that artificial sweeteners CAUSE any kind of cancer, just that the people who tended to consume more artificial sweeteners also happened to get cancer slightly more often than people who didn’t. They attempted to control for factors like age, sex (except for in regards to breast and prostate cancer), smoking, family history, and things like that, but if there is an effect it could be that people who are more likely to get cancer are also more likely to switch to a “healthier” drink like Diet Coke instead of regular Coke.
It was also a very small effect size: an increase of 13%. To put that into perspective, the most common cancer they cited was breast cancer. According to the American Cancer Society a woman’s baseline risk of getting breast cancer is (also) 13%. If you increase that by 13%, a woman who chugs diet sodas might expect her risk to increase to 14.7%.
And I do mean “chug,” because the effect was seen for people drinking more than a 2-liter bottle of soda every day. Which, by the way, was self-reported – self-reported diet data is notoriously inaccurate, as reported in many studies on the subject like this 2020 meta-analysis that found rampant underreporting of calories, especially from subjects at high BMIs. Considering that the French study says the most common cancers they saw increase were those associated with higher BMI, that might be very relevant.
Another issue worth noting with this study is that if you look at the raw data, the researchers actually found that in some cases, the people who consumed more artificial sweeteners had a lower cancer risk than the people who consumed some artificial sweeteners, and in the case of sucralose (the least popular sweetener, so the one with the least amount of data) the heaviest consumers actually had a DECREASED cancer risk. If the artificial sweeteners are causing cancer, wouldn’t we expect to see risk consistently increasing with use, especially for the sweeteners where the sample size is huge?
Finally, the point that I have to bring up every single time anyone claims artificial sweeteners are dangerous: these correlated increases in risks are rarely compared with consumption of sugar. Excess consumption of sugar isn’t just suspected to be bad for you, it’s absolutely confirmed without a doubt: excess sugar increases your risk of cancer, heart disease, diabetes, liver damage – you name it, sugar exacerbates it. A 15-year Harvard study found that people who consumed a lot of sugar had a 38% increased risk of dying of cardiovascular disease. Because I calculated the absolute versus relative risk for artificial sweeteners and breast cancer, here it is for sugar and cardiovascular disease: as the leading cause of death in the US, your risk of dying from heart disease is 25%, meaning that excess sugar might cause that to jump from 25% to 35%. And that’s not your risk of contracting heart disease – DYING from it. And sure enough, buried in the supplemental materials I found that these French researchers DID show what happened to cancer risk when considering total sugar intake as well as artificial sweeteners: people who reported eating more sugar than nutritional guidelines saw their risk increase dramatically over those who reported eating below the guidelines. In fact, people who consumed NO artificial sweeteners but DID consume more sugar had nearly the same increase in cancer risk as those with the highest consumption of artificial sweeteners but less sugar intake.
So consider that the next time you want a soda and are choosing between the one with real sugar and the one with artificial sugar: would you pick the one that increased your actual risk of getting breast cancer by 1.7 percentage points, or the one that increases your risk of dying from heart disease by 10 percentage points?
That said, while the risks of consuming too much added sugar are well-documented in thousands of studies over the past several decades, where the question isn’t IF it’s deadly but exactly how deadly it is, none of that is even close to being true for artificial sweeteners. The FDA reports that aspartame is “one of the most exhaustively studied substances in the human food supply, with more than 100 studies supporting its safety.” The evidence required to overturn this conclusion is expansive, and it cannot be done with one study looking at self-reported data that attempts to (but cannot possibly) control for other mitigating factors, which found a correlation between artificial sweetener use and a very very small increase in the risk of some cancers.
The moral of the story? Don’t panic. Just consume things in moderation and you’ll live forever.