Xylitol

Xylitol is a sugar alcohol, which means it is neither a sugar nor an alcohol, and the name misleads on both counts. It occurs naturally in small amounts in fruit and is manufactured from birch or corn, which is why “birch sugar” appears on some labels and means the same thing.

It is about as sweet as sugar, which makes it unusual in this family. Most sugar alcohols are noticeably less sweet and need bulking out.

Why dentists are interested

This is the part that separates it from the rest of the category, and it is a genuine finding rather than a marketing claim.

The bacteria most associated with tooth decay ferment sugars and produce acid as a by-product, and the acid is what damages enamel. They take xylitol up and cannot ferment it. So a sweetener that tastes like sugar sits in the mouth doing none of what sugar does there.

That is why xylitol appears in chewing gum, toothpaste and mouthwash rather than only in diet products, and why it is the one member of this family that dental bodies actively suggest rather than merely tolerate.

For blood sugar

It raises glucose considerably less than sugar and delivers roughly forty percent fewer calories, which is the reason it appears in products aimed at people counting carbohydrate.

The catch is one it shares with the whole family: the US rule makes declaring how many grams a product contains voluntary, so a product built on xylitol need not quantify it. The ingredient list names it because ingredients must be named, but naming is not quantifying. That gap is set out on the page for reading labels when you are watching blood sugar.

Like Sorbitol, what is not absorbed draws water into the bowel, so ordinary portions cause digestive trouble in some people. Tolerance varies widely and builds with regular use.

The dog problem

This is the urgent part and it belongs high on any page about xylitol.

Xylitol causes a severe drop in blood sugar in dogs, and at higher doses liver damage. The quantities involved are small: a few pieces of sugar-free gum can be enough for a small dog. Peanut butter is the route that catches people out, because it is the food most often used to hide medication or fill a toy, and some brands sweeten it with xylitol.

If a dog eats something containing xylitol, that is a veterinary emergency and not a wait-and-see. Nothing about this applies to people, and the two facts get muddled constantly.

Where it turns up unexpectedly

Toothpaste and mouthwash, where swallowing a small amount is normal and unremarkable for a person.

Sugar-free gum and mints, which is the largest use by far.

Some peanut butters, some baked goods sold as low carbohydrate, and some supplements and chewable medicines, where it does the sweetening a syrup would otherwise do.