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Xylitol: How toxic is it? Keep it away from your dog

February is National Pet Dental Health month so I thought I would write about something to do with dental health and pets. In this case it is human dental health and dogs.

Xylitol is a commonly used sugar substitute that is found in the fiber of many fruits and vegetables. Although it was first discovered in the late 19th century, xylitol became popular in the 1970s in Finland after scientists learned of its dental benefits. After extensive research by Finnish scientists it was found that not only does xylitol contain less calories than sugar (making it safer for diabetics), but also has plaque-reducing effects from inhibiting certain bacteria. Now many gums, mints, mouth washes, toothpastes and even pastries are sweetened with xylitol.

Unfortunately, as great as xylitol is as a sugar substitute for people it is just as dangerous to dogs. Only a small amount of xylitol (a single pack of gum or two small muffins) can be deadly to dogs. Xylitol causes a rapid rise in insulin levels which can lead to a life threatening hypoglycemia (low blood sugar episode) within an hour. Mild symptoms will include vomiting and disorientation. More severe signs are collapse, seizures and even death.

If the drop in blood sugar is corrected, a secondary injury to the liver can occur within hours — something called "acute hepatic necrosis." Acute hepatic necrosis refers to death of the liver cells all at once. How xylitol triggers this is not known. Many veterinary toxicologists believe that either the drop in blood sugar depletes the ATP stores in the liver, or that oxygen free radicals develop as a breakdown product of xylitol metabolism. Either way the end result is acute hepatic necrosis.

Adenosine triphosphate, or ATP, is a molecule we all learned about in high school biology. If one remembers the Kreb's cycle (the diagram that illustrates aerobic metabolism in all living cells) then one remembers ATP. All the steps of the Kreb cycle were always confusing to me and I still don't have it down but another name for ATP was introduced to me after I graduated from veterinary school. At a conference the lecturer called ATP "the currency of life." This made a lot more sense because we started talking about cellular metabolism and how all the systems within each individual cell start to break down without adequate amounts of ATP available at all times. If without ATP for too long the cell dies.

Oxygen free radicals can result from any number of injuries: trauma, poisoning, infections, etc. These substances enter cells and destroy the DNA. If the DNA fails the cell may have all the ATP it needs but does not know what to do with it. The cell dies soon thereafter.

The good news is the liver can repair itself if the damage is not too great. The bad news is some of these patients will actually go into liver failure and do not recover. So remember, as much as xylitol is harmless (and in many cases beneficial) to people keep all of your sugar free gum and treats away from your dog. Also remember to visit your veterinarian this month to have your pet's teeth examined.

Dr. Kearns has been in practice for 13 years and is pictured with his son Matthew, and the newest member of the family, Jasmine, a Labrador retriever.

Author: 
Matthew Kearns, DVM