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Now, on to this week.

You may have seen a headline making the rounds again: "six sugar substitutes linked to faster brain aging." It landed a little personally for me. I spent most of a decade on strict keto and sometimes used erythritol and xylitol although they were never my go-tos (thankfully). So many sugar-free recipes call for them still today.

’ve been thinking about this topic for years and I recently published the article I’ve wanted to write: the three sugar-free sweeteners I use now and the five I avoid. Erythritol is on the avoid list and it’s not something I’ll use going forward. The link to my article is below, but first, here’s what that brain study actually says, because it’s more interesting (and less scary) than the headline.

The research is real, published in Neurology in 2025. It followed 12,772 Brazilian adults for about eight years, checking their memory and thinking across three rounds of testing. Researchers asked at the start how often people ate seven specific low and no calorie sweeteners, among them aspartame, saccharin, acesulfame K, erythritol, sorbitol and xylitol. This kind of recall/reporting type of study is rife with data problems anyway.

The people who reported eating the most of these declined a little faster on memory and word-finding tests than the people who ate almost none. Six of the seven showed the pattern and that is the part that became the headline.

Here's what almost no one mentioned. The link only showed up in people under 60. In the group 60 and older, there was no association at all.

That's the opposite of what you'd expect from a "this ages your brain" story. It does put those of us in midlife in the group where the signal appeared, but it also makes the simple cause-and-effect version harder to believe. If these sweeteners were plainly toxic to the aging brain, you'd expect the effect to be strongest in the oldest group, not missing from it entirely.

A few honest flags about the study, because this is how studies get overblown.

It's observational. It can show that two things travel together, not that one causes the other. People who drink a lot of diet soda or live on protein bars tend to differ in a dozen other ways and the authors say they couldn't rule all of that out.

Diet was measured once, at the very start, with a questionnaire and then assumed to hold for eight years...I mean what?!?! How many times have you shifted your diet over eight years...exactly the problem. The effect sizes were small. The authors frame the gap as roughly a year and a half of extra cognitive aging and that's their translation of test-score slopes, not anything measured on a brain scan.

Now the part I found most interesting, given my own list. Every sweetener on my avoid list that this study measured (erythritol, xylitol, aspartame and sugar alcohols like sorbitol) showed up in the link. But this study isn't why they're on my list. I stopped using erythritol because of the heart and platelet research from the last few years, which is more directly negative than this study. The brain study is a supporting note, not the reason.

And the three I do use, allulose, pure stevia and monk fruit without erythritol, weren’t tested here at all. So this study can’t tell you they’re safer, and it isn’t evidence they’re worse either. Anyone telling you to “switch to monk fruit because of this study” is going past the data we have at this point. My reasons for choosing them are their own after years of research and they’re all in the article, with my caveats included.

One practical note before you go shopping. These sweeteners hide well beyond diet soda and sugar-free gum: a lot of protein bars, "sugar-free" desserts and some protein powders.

In fact, the only protein bar I used switched from allulose (I had been so happy to finally find a bar that used it) to aspartame and sweeteners not on my approved list. You have to watch out for this, particularly when a smaller health-focused brand is bought out by “big food.” Plenty of powdered stevia and monk fruit products are bulked up with erythritol, so read the ingredient list, not just the front of the bag...and check even trusted labels again every once in a while.

→ The 3 sugar-free sweeteners I use (and the 5 I avoid)​

Hit reply and tell me which sweetener lives in your pantry right now and whether reading this changes anything for you. I read every reply and I always write back.

And if you know someone who's been side-eyeing her diet soda since that headline, forward this to him or her. I'd love to have them here!

Have a great weekend, Cheryl

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