You are always told that dogs can’t eat chocolate, and the reason for this is simply because it contains a poisonous plant chemical called theobromine, which is naturally found in cocoa. Theobromine is structurally similar to caffeine, and has similar stimulating (and toxic) effects in the body when consumed. It is this chemical which makes chocolate poisonous to dogs and other animals.
Really, this is the question people should be asking. Theobromine, is chemically similar to all other plant alkaloids, which animals and humans consume all the time with no ill effects. Just think – when was the last time you ate some chocolate – did you feel ill at all?
All plant alkaloids, including theobromine and caffeine, are toxic in the right (or rather, the wrong) dosage. However, dogs are particularly susceptible to theobromine toxicity – but why?.
The answer lies in the dogs metabolism of alkaloids. Humans can metabolise compounds like theobromine pretty quickly and efficiently The half life of theobromine in humans is 2-3 hours, and this means that if you consume 100mg of theobromine, in 2-3 hours, your liver will have metabolised half of it, and so only 50mg will be left in your body. The risk of toxicity from theobromine is so low in humans that there are no health warnings for theobromine consumption from bodies such as the World Health Organisation (WHO).
The toxic dosage for humans is thought to be in excess of 1000mg per kg of body weight, which would be about a kilo of dark chocolate per kg body weight. As delicious as dark chocolate is, there is very little risk of someone eating 60+ kilos of dark chocolate and getting ill from theobromine (especially considering how fast our body metabolises it).
The half-life of theobromine in dogs on the other hand is 18 hours.This indicates a very poor ability to metabolise and break down theobromine in the liver of dogs, making the toxic dosage much lower than that humans.
Dogs typically don’t have many plants in their diet, and so their inability to metabolise these plant chemicals may be simply due to a lack of need throughout their evolution. Whereas humans have a more varied diet, higher in plants, and so are much better adapt at metabolising these chemicals.
This poor ability to metabolise theobromine effectively makes the lethal dosage for dogs around 250-500mg per kg of body weight. This is still relatively hard to achieve, but this is the fatal level, and dogs will show the symptoms of theobromine toxicity at a much lower dosage. Small dogs, such as a pug, can suffer from vomiting from as little as 5mg/ kg body weight, which is only 20-30g of dark chocolate.
Cats are even more susceptible to the toxic effects of theobromine than dogs (toxic at 200mg/kg), but you don’t often hear the risk it poses to cats. The reason for this is simply how each animal behaves.
Dogs will eat anything they get their jaws on – I’ve known dogs to eat a whole loaf of bread just because it can reach it on the kitchen surfaces! Cats however, take a much cooler approach to food – they will lick things, and nibble, but are much fussier, and less greedy.
So the canine downfall is its appetite and weak metabolism of plant chemicals.Not to worry though, all this means for you is keep your chocolate out of reach of animals and everyone will be happier!
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Dogs can’t eat chocolate because it contains a chemical called theobromine in, which is toxic to dogs.