Artificial sweeteners are in the news almost constantly.If you believe the headlines, they are terrible blights on our health that are far worse than the sugar they replace.This isn't always supported by the evidence, but it's something that we love to hear, and so it gets reported on almost weekly regardless of what the data actually shows.The most recent furor over artificial sweeteners is a perfect example. The headlines have been claiming for months that artificial sweeteners speed up cognitive decline.According to a recent study, there are six of these 'dangerous chemicals', including common ones like xylitol and aspartame, that may be causing our brains to rot more quickly.(PatriciaEnciso/E+/Getty Images)The study has been covered by hundreds of media outlets (for full disclosure, ScienceAlert didn't report on that paper specifically, but we do write a lot about recent findings on artificial sweeteners!).Despite being published in September 2025, it's still making headlines in the second half of 2026.
"This is all made especially remarkable given that it doesn't really show any issues from artificial sweeteners at all." – epidemiologist Gideon Meyerowitz-Katz
This is all made especially remarkable given that it doesn't really show any issues from artificial sweeteners at all.The study itself is a very simple piece of observational research. The authors took a cohort of public servants in Brazil called the ELSA dataset. This is a longitudinal study which measured people's brain function over time using a standard battery of tests.At the start of the study, people also filled in very extensive questionnaires about their lives, including what's called a food frequency questionnaire, which measures what people say that they eat – NOT what they eat.This is important, and we'll get back to it.The authors looked at the correlation between reported sweetener intake – calculated from those food frequency questionnaires – and cognitive decline as measured using four different scales. Over the eight years of the study, they found that people in the highest third when it comes to sweetener intake had a modest amount of additional brain aging compared to people in the bottom third.This research suffers from the normal issues that such observational studies do.One big thing is that food frequency questionnaires don't really measure intake of food. They measure what people THINK they eat, but we know that we are often unreliable historians.Most of these questionnaires ask about the last 12 months of eating, and people rarely remember their food intake for that long with any degree of accuracy.The analysis also assumes that people's food intake didn't change over the course of the study.The authors only had a single food frequency questionnaire to rely on, which meant that if people changed their food intakes over this period, there would be no way for them to know about it.As letters to the journal have noted, there are also serious questions about the biological plausibility of the claim.Some of the sweeteners are natural substances, one is actually a very rare form of sugar, and all of them are very different molecules. It would be extremely unlikely for all of these different chemicals to have the same impact on the brain.There's also the problem of reverse causality – that is, people who were already experiencing brain declines due to diseases like diabetes or heart disease may have been more likely to eat and drink artificial sweeteners at the start of the study.
