Erythritol and xylitol are both polyols. Both are low (not zero) calorie substitutes for sugar. I think erythritol has ended up in a lot more commercially produced "foods" (in quotes because IMO if it comes out of a factory it isn't food) as they're absorbed differently. Xylitol is not absorbed, and so if large quantities are consumed, there's a reaction from the microbiome (from what I've read, that reaction is health-positive but uncomfortable). Erythritol is absorbed (so no stomach upset) and is notionally 'inert', but it's absorbed and then present in the blood plasma. What could possibly go wrong?

Given the plasma levels seen I'd expect that we're bad at separating it out for excretion. Found a study here, key quote: "Renal clearance of erythritol was approximately half that of creatinine, indicating tubular reabsorption of erythritol by the kidney." (reabsorption means the kidneys are pulling it back out of the urine before it’s sent off to the bladder)

As a side note, xylitol is highly toxic to non-humans. (think dogs, cats... or bacteria). The process that breaks down glucose takes initial energy - and produces something called pyruvate (glucose split in half), which in turn is used for cellular respiration. Xylitol prompts the reaction, then energy expenditure - and then no useful product. Dogs die of liver failure, bacteria of energy stores depletion - and we humans just poop it out, after our microbiome uses some. I was concerned about those bacteria, but after posing that question, I got bombarded with links showing it was a net-positive by someone offended that I’d consider PubMed a good place to look for info (?!?) but the linked studies were sound.

I got interested in xylitol (and the other polyols) after suffering a brain infection post-teeth-cleaning from strep bacteria already in my mouth. I now chew xylitol sweetened gum on the way to the dentist. :-)