The Skinny on Xylitol, Stevia, Aspartame and Other Sugar-free Stuff

Pack of Gum
Xylitol, an ingredient in many sugar-free gums and mints, leads to a rapid drop in blood sugar for dogs.

To most of you, it only makes sense to keep that sugar-free German chocolate cake away from your German Shorthaired Pointer. Not only is it made of chocolate (which everyone knows is verboten for dogs), but it also might contain something far worse. But not everyone knows of the evils built into some breeds of sweeteners.

For example, last week I received this email from a confused dog owner: “I just read on the Internet that aspartame causes pets to go blind and get brain damage. Is this true, or is it only another Internet horror story?”

Well, yes. It’s another one of those online rumors that goes viral before anyone gets a chance to confirm its veracity. Aspartame, while probably not particularly good for anyone, has very few serious side effects in dogs and cats that we know of. Not at the doses offered in consumer products, anyway.

But I have a sneaking suspicion I know how the rumor got started. A few years ago, I received one of those mass emails written by a bereaved dog owner who claimed her dog suddenly went blind, fell over and died after eating sugar-free yogurt containing aspartame.

After searching the Internet thoroughly (she claimed), the owner concluded that methanol poisoning as a result of aspartame ingestion was what killed her dog. The rumor reportedly sent thousands of pet owners into spasms of artificial sweetener-related anxiety.

But never fear: Aspartame will typically not lead to sudden death. Not in dogs or cats.

Nonetheless, it is true that aspartame will be metabolized into methanol by the body. And because methanol toxicity can lead to blindness and brain damage in humans, thus (presumably) the rumor was born.

The thing is, methanol is metabolized differently in dogs and cats from in humans. A small amount of methanol may cause some gastrointestinal upset, but it's not likely that a mammal can eat enough aspartame to cause serious problems. Consequently, I’m here to tell you that aspartame poisoning in dogs and cats is highly unlikely. (Which, to clarify, is not to say I consider aspartame in any way beneficial.)

Xylitol May Have Been to Blame

What more than likely happened to occasion this dog’s death, if indeed the story was true (beware: many Internet memes are not), is that the dog consumed a sugar-free yogurt containing xylitol, a sweetening substance increasingly found in all sorts of sugar-free consumer products. Toothpaste, mouthwash, gums, mints, candy, desserts, yogurts and even some of those kids' vitamins and syrupy medications contain xylitol.

Because xylitol leads to a rapid drop in blood sugar, many dogs will collapse and suffer seizures. If they’re not rushed immediately to the hospital, they often die. In some cases, sudden death will ensue even before any other signs. And if they survive, they may suffer life-threatening liver failure.

Unfortunately, many pet owners (and even some pet health professionals!) are still unaware of this “natural” sweetener’s extremely toxic effects. In fact, depending on the amount ingested, it can be way more toxic to dogs than chocolate. And yet most dog owners are still in the dark about the poisons that lurk in their pockets and purses.

So if you ever believe your dog has been exposed to xylitol (or any potentially toxic substance), contact a pet poison control center and get to your veterinary clinic as soon as possible!

Note: Cat owners can rest easy. Not only are cats not adversely affected by xylitol (that we know of), but because they’re not attracted to sweet things (they don’t have taste buds that register “sweet”), they’re also less likely to expose themselves to xylitol or any other sweetener. (Enticingly creamy delicacies are an exception.)


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