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Toxic chocolate

As Easter approaches many people begin to think about consuming their own bodyweight in chocolate. But Dr Karl warns that it should be you that does the munching and not your dog.

The Latin name for the cacao tree, from which chocolate comes, is Theobroma cacao. The name means "food of the gods", and chocolate-lovers agree. But people also love their pets. So should you share the love around and feed your pet some chocolate? Definitely not, because chocolate can kill pets, especially dogs.

Chocolate comes from the cacoa tree, which grows some 6-12 metres tall. After about four years, the mature cacao tree begins to make its fruit - the pod. There are up to 70 pods, each about 35 centimetres long, and ranging in colour from deep purple to bright yellow. Inside each pod are about 20 - 60 beans, each about 2 - 3 centimetres long. This is the Mother Lode of Chocolate.

The farmers remove the beans and bury them in large piles, so they can ferment. This is when the flavour begins to develop. After a few days, they are roasted, to remove some water, to develop the flavour further, and to drop the acidity and the bitterness. Then the beans are popped out of their shells and ground up.

In the World of Chocolate, there is a special word called "conching", which means to stir and aerate. Depending on the quality, the gluggy brown chocolaty mess is conched for between four and 72 hours, while being heated to between 55°C and 88°C. If you cool this down into 5 kg blocks, you have your basic chocolate.

Baking chocolate and dark chocolate are usually quite bitter, because they have no or little sugar added. Sweet chocolate has (of course) sugar added, as well as a whole bunch of other flavourings such as vanilla. To get milk chocolate, you add milk. The baking and dark chocolate have the highest amounts of pure cacoa, up to 85%.

Chocolate was drunk by the Preclassic Maya some 2,500 years ago. They frothed it into a foam by repeatedly pouring the liquid from one vessel to another. By the time of the Spanish Conquest of Middle and South America, chocolate was drunk with most meals, and usually mixed with another ingredient such as water, honey and chilli.

Columbus in 1502 brought back some cocao beans to Spain. The Spaniards did manage to keep the secret of their bitter but delicous drink for a century. Chocolate remained a drink until 1847, when J. S. Fry & Sons came up with a solid form of chocolate.

Cacao has over 500 different chemicals, including a few in the methylxanthine class. The two methylxanthines that we humans seem to love are caffeine and theobromine. The theobromine seems to be the dog killer.

The toxic dose of theobromine is 100-150 mg/kg of body weight. It turns out that different types of chocolate have different amounts of theobromine. Milk chocolate has 154 mg of theobromine for each 100 gm of chocolate, while for the same weight, semisweet chocolate has (528 mg) 3 - 4 times more, with bitter baking chocolate carrying a massive (1,365 mg) 9 times more of theobromine.

So for your "average" 20-25 kg family dog, the fatal dose of chocolate is about 1.5 kg of milk chocolate, about 400 gm of semisweet chocolate, and 140 gm of baking chocolate - which is not a lot of chocolate for a dog to scoff. The dog could suffer seizures or convulsions, blueish skin and a fast irregular heart rate as it heads down theobromine's lethal pathway.

You definitely need to see a vet immediately, who may try to stabilise the dog's breathing, heart rate, electrolytes, acid-base balance and over-excited nervous system, as well as remove any remaining chocolate from the dog's gut. So yes, chocolate can kill your dog.

Chocolate can have similar effects on humans, but again, usually only with massive overdoses.

However, in small doses, chocolate definitely seems to be good for you - especially if it's dark chocolate. Cacao contains chemicals that fight the bacteria that cause tooth decay. On the other hand, milk chocolate is rich in sugar that feed these bacteria.

Other good chemicals in chocolate keep the blood vessels both elastic (which is good) and wide-open (which is also good). And of course, that matches your kids' mouths, which are also elastic and wide-open for chocolate.

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