As mentioned in this column last week, most pet owners have heard chocolate can be toxic to dogs. If so, how so?
If dogs eat enough chocolate, life-threatening cardiac rhythm disturbances and central nervous system dysfunctions can result. This is true for many species. Even livestock deaths have been reported from those fed cocoa by-products or mulch from cocoa bean hulls.
According to veterinary toxicologist Sharon M. Gwaltney-Brant, writing in the Merck Veterinary Manual, the two killer compounds in chocolate products are theobromine and caffeine. The former is usually present at 3 to 10 times the amount of caffeine. Both, known collectively as methylxanthines, are responsible for what’s called chocolate toxicosis.
How much of the chemicals are in which chocolates varies widely. It even varies more depending on the type of chocolate. White chocolate, for example, is safe. Before we get into how much is where exactly, let’s talk about the lethal nature of the compounds.
The term LD50 comes into play here. That term refers to the dosage of a toxin required to kill half the population receiving it after a specific period of time. So for both chemicals noted in chocolate, the LD50 is about the same, about 100 to 200 milligrams per kilogram of body weight.
Gwaltney-Brant is quick to note, though, that severe signs and death can happen to individuals at much lower dosages, in part because individual sensitivity to the chemicals can be high.
Mild signs of chocolate toxicity, nausea, vomiting and excessive thirst, can occur with as little as 20 mg/kg. Toxicity affecting the heart can happen at the 40 to 50 mg/kg. Seizures occur once the dose gets to 60 mg/kg or higher.
So now back to how much is available in which chocolates. Dry cocoa powder, which many of us have in our cabinets for cooking, contains about 800 mg/oz. of product. Unsweetened baker’s chocolate comes in at about 450 mg/oz. Typical chocolate chips is next at 150 to 160 mg/oz. Milk chocolate, like the kind we make s’mores with, drops to about 64 mg/oz. And finally, if you buy expensive dark chocolate, typically around 65 percent cacao, that provides about 300 mg/oz.
To put this in relative terms, according to the label, seven Hershey’s Kisses constitute one human serving, about 32 grams. That’s a little more than an ounce for a total dose of about 160 mg. Let’s say your pooch weighs 40 pounds or just more than 18 kilograms. Suffice to say, your pooch is likely in the safe zone, but watch closely.
One estimate says a 10 year-old child would have to eat, and keep down, 1,900 of the popular candies to die.
But dogs are different beasts, so in a word, beware. Beware where you place chocolate in your home and prevent pets from getting into it.
Once ingested, chocolate melts in the stomach and is readily absorbed from the gastro-intestinal tract. There, it circulates quickly throughout the body to eventually be metabolized in the liver. The leftovers and some of the parent compounds leave the body in the urine.
The problem is, dogs metabolize this relatively slowly, so if they keep eating chocolate, the toxic levels can increase faster than they are processed and eliminated.
The central nervous system effects include increased stimulation, urination and a racing heart. The chemicals in chocolate do lots of other things at the metabolic level, and they also increase some hormones that counteract each other.
Treatment is to cause vomiting if the symptoms haven’t occurred but are anticipated. After the onset of symptoms, care is supportive mostly and is adjusted for individual symptoms.
Charlie Powell is the public information officer for the Washington State University College of Veterinary Medicine, which provides this column as a community service. For questions or concerns about animals you’d like to read about, email email@example.com.