Is It Possible to Overdose on Chocolate?

Americans buy 90 million pounds of chocolate during the week of Halloween, a marveling statistic widely reported by various news sources. With all that chocolate floating around, it’s intriguing to consider whether eating too much of this confection can kill.

In humans, the main health risks of chocolate overindulgence are obesity and cavities. But chocolate does contain trace amounts of poison. It is derived from the roasted seeds of the plant Theobroma cacao, with the main toxic components being the methylxanthine alkaloids theobromine and caffeine.

The LD50 for theobromine, or lethal dose required to kill 50 percent of all people, is 1,000 mg/kg of body weight, which translates to 75 g of theobromine in a 75-kg person. Notably, theobromine levels vary by chocolate type, with cocoa powder and dark chocolate containing the highest concentrations, followed by milk and white chocolate. Nevertheless, it would still take perhaps a pound of pure chocolate to kill a human by means of theobromine poisoning.

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Theobromine interferes with the nervous system, respiratory system, and cardiovascular system (e.g., vasodilation), as well as results in excess urination (i.e., diuresis). In very high amounts, it can cause increased heart rate, sweating, trembling, loss of appetite, severe headache, and drops in blood pressure. In reality, other associated symptoms like nausea and anorexia would make it difficult for any person to continue eating chocolate until quantities become fatal. Nevertheless in the literature, there have been a few reports of elderly people exhibiting lower-level theobromine reactions.

Like humans, dogs love chocolate. In dogs, however, theobromine found in chocolate can be much more deadly, and even a moderate amount can do serious damage. (The LD50 in dogs is 100-500 mg/kg, and most dogs weigh far less than humans.) Moreover, chocolate is metabolized slowly in these animals, and it can take days to clear the body by means of liver breakdown and subsequent voiding.

Authors of an article published in the BMJ warned of theobromine poisoning in dogs. “Most symptoms will begin to appear within two hours of ingestion, but, as theobromine is metabolised slowly, it can take as long as 24 hours for them to appear and up to three days for recovery. Although there is no specific antidote, supportive management includes induction of vomiting and administration of activated charcoal, oxygen, and intravenous fluids,” they wrote.

Although a dog may be given a very small amount of real chocolate every once in a while, it is best to find sweet treats made specifically for pets. And if you’re wondering, cats can tolerate even less chocolate (i.e., theobromine). So this Halloween season, please keep your family’s candy stash hidden from the prying paws of pets.