Most dog owners go into a panic if their pet makes a lunge for the candy bowl — but is this worry really necessary?

Theobromine, a bitter chemical found in cocoa beans, is the molecule in chocolate tied to illnesses in canines. But how much theobromine is there in most chocolate? And how much theobromine would it take to kill household pets? It turns out, you might be more likely to die by chocolate than your dog.


Theobromine, the danger in chocolate
Structurally, theobromine is one methyl group away from caffeine, and the duo are often found together. When isolated, theobromine is a white, crystalline powder with a bitter taste. The molecule is naturally found in cocoa beans, the main component of chocolate.

Physiologically, theobromine widens the blood vessels, causing a decrease in blood pressure. The molecule also acts as a diuretic, general cardiac stimulant, and in some cases, it alleviates asthma symptoms. Humans metabolize theobromine very quickly, much quicker than canines, and this is a part of the problem for man's best friend.


Cats lack the capacity to taste sweet foods (dog owners, feel free to use this fact in arguments of dog vs. cat superiority), leaving felines less susceptible to poisoning, since there's little reason to keep eating chocolate — without its sweet and/or bitter flavor, chocolate simply becomes a waxy solid.

How much theobromine is in chocolate?

Dogs dying from a theobromine overdose perish due to a combination of heart problems and respiratory failure. The amount of theorbromine necessary to kill one out of two members of the canine population (the LD50) is 300 milligrams per kilogram of body weight. Toy breeds like Yorkshire Terriers weigh around 3 kilograms, Cocker Spaniels weigh about 15 kilograms, while larger breeds like a Dalmation or St. Bernard weigh in at 25 and 90 kilograms, respectively.


Using this value of LD50, 900 milligrams of theobromine would kill your average Yorkshire Terrier, but is this a lot of chocolate? A single Hershey's Kiss contains 8 milligrams of theobromine — your tiny Yorkshire would need to consume well over 100 milk chocolate kisses before nearing death's door, an unlikely scenario. The considerable difference in weight between breeds also poses a problem here — what would kill a Cocker Spaniel would not even faze a St. Bernard.

Dark chocolate is the killer

As we move from milk chocolate to dark chocolate, the amount of theobromine increases, decreasing the quantity of chocolate your dog needs to eat before finding out if all dogs truly do go to heaven. The boutique Scharffen Berger 82% Cacao Extra Dark Chocolate contains 1100 milligrams per $3-4 bar - enough to easily meet the LD50 for a small 3 kilogram dog. A typical Cocker Spaniel would need to eat five of these large (129 gram) bars before death comes into the equation, quite a large amount of chocolate.


Could dark chocolate kill you?
Theobromine, in substantial quantities, can poison humans, with the elderly particularly sensitive to the molecule. The LD50 (amount of a molecule necessary to kill 50% of the population) for humans for theobromine is 1000 milligrams per kilogram, over three times that of a dog, but a very manageable number — especially when taking into account the human propensity for gluttony.

Looking at a range of human weights between 60 kilograms to 100 kilograms, consuming between 54 and 91 bars Scharffen Berger 82% Cacao Extra Dark Chocolate would allow an individual to reach the LD50 for humans. That's seven kilograms of chocolate for a person weighing 60 kilograms and 12 kilograms for someone weighing 100 kilograms. Eating 12% of your body weight in chocolate is an unusual way to shuffle off this mortal coil, but possible.


A phenomenal amount of milk chocolate is necessary to harm even smaller dogs. Thanks to the enormous amount of chocolate necessary to put your dog in danger, I would argue that you are more likely to die from a theorbromine overdose than your canine pal.

Top image from Dell Comics Lassie series. Additional images from the Hershey Company, Sources linked within the article.