Why is chocolate toxic to dogs, cats, and other animals?
Pets, and especially dogs, digest the alkaloid theobromine much slower than humans. Consuming chocolate can be toxic and even lethal to dogs, cats, and other animals. Image by @ciabattespugnose
Chocolate can be toxic to some animals due to the alkaloids contained within cocoa beans, the main ingredient in chocolate. These alkaloids, theobromine and caffeine, are metabolized more slowly in animals than in humans. Due to this difference in metabolism, certain amounts of theobromine and caffeine consumed by animals may become toxic as they may overstimulate their system to the point of illness or even death.
Caffeine and theobromine are considered methylxanthines. You may be familiar with this term if you have asthma. Methylxanthines are used as bronchodilators, vasodilators, analeptics, diuretics, cardiotonics, and misused for doping (in human sports or even animal races). Therefore, it’s not hard to understand how these compounds can harm your pet if these remain in their system longer or react more strongly than they do for humans.
Theobromine & Caffeine Impact On Pets
Both theobromine and caffeine have a stimulant effect on the body. For humans, the effect of theobromine form chocolate is quite negligent, and the amount of caffeine in chocolate is more equivalent to green tea than it is to coffee. So for humans, the stimulant effect of chocolate is quite low, unless you’re consuming a great deal.
For many animals, especially smaller ones, the consumption of theobromine and caffeine has a greater impact in regards to the stimulant effect of theobromine and caffeine. The breakdown and excretion of theobromine is much slower in animals, and particularly in dogs. As it is not excreted or broken down fast enough, it can overstimulate the dog’s nervous, respiratory, and circulatory system.
If dogs, cats, or other animals, consume too much theobromine and caffeine, it can lead to issues such as thirst, restlessness, weakness, convulsions, vomiting, cardiac arrhythmias, and in some cases even death. However, although chocolate should not intentionally be fed to pets, if they accidently consume a small amount there may not ne necessarily be a reason to panic. That is, there are thresholds where eating a small bite of chocolate may not result in extreme illness of the pet. When your dog, cat, or other pet has consumed chocolate, it is best to call your local veterinary clinic to see how you should proceed. In some cases if too much was consumed, the vet may need to induce vomiting, especially within the first couple of hours of consuming the chocolate.
Type of chocolate matters
These alkaloids are found within the cocoa bean, the seed used to make chocolate. Therefore, the greater the percentage of the cocoa bean, the greater amount of these alkaloids in the chocolate. For instance, higher percentage dark chocolate has far more greater amounts than milk chocolate. White chocolate has nearly none, since white chocolate is made from only the fat of the cocoa bean (which we refer to as cocoa butter), and the alkaloids are predominantly found in the cocoa solids (any part of the seed which is not cocoa butter).
When symptoms occur
There may be no symptoms if a very small amount was ingested for the body weight of the animal. In most cases, if too much was ingested, the initial symptoms will manifest 2-4 hours after ingestion. If very high levels of dark or milk chocolate was consumed, then death may result after 18-24 hours. If smaller amounts were consumed over a period of days, then this may slowly result in heart failure.
Animal Welfare and Doping
Some races and animal sports may test animals (such as dogs) to assess for doping and welfare of the animal in question. Therefore, it may be important for some pet owners to keep chocolate and other caffeine products away from pets that may be tested in case of accidental ingestion.
Levels of Theobromine & Caffeine in Chocolate
Different types and percentages of chocolate contain different levels of theobromine and caffeine. The higher the percentage, or darker the chocolate, the more theobromine and caffeine is contained. Here are some examples:
Milk chocolate (25-30% cocoa) - Theobromine 0.5-2.3 mg; Caffeine 0.1-0.9 mg/g
Dark (55%) Theobromine 5-8.5 mg/g ; Caffeine 0.5-2.6 mg/g
Dark (70%) Theobromine 5.5-12.7 mg/g; Caffeine CA 0.7-3 mg/g
White Chocolate Theobromine 0.01 mg/g; Caffeine 0.03 mg/g
What level is toxic or lethal to pets?
Suggested levels of caffeine and theobromine toxic or lethal to pets. This is according to the weight (per kg) of the animal. Keep in mind that below lists lethal amounts for dogs and cats, but lower amounts can still have harmful impacts to your pet and should still be taken seriously (such as contacting your veterinarian).
Caffeine
In laboratory animals, a toxic level of caffeine for mice and rats in mg per kg of body weight is 127 and 192 respectively
For dogs, it is suggested that a minimum of 140-150 mg/kg body weight of caffeine is lethal.
For cats, it is suggested that a minimum 100-150 mg/kg body weight of caffeine is lethal.
Theobromine
In laboratory animals, a toxic level of theobromine for mice and rats in mg per kg of body weight is 837 and 1265 respectively.
For dogs, it is suggested that a minimum of 250-500 mg/kg body weight of theobromine is lethal.
For cats, it is suggested that a minimum 200 mg/kg body weight of theobromine is lethal.
When to decontaminate?
This would likely be considered by a veterinarian. Give them an idea of how much chocolate your pet may have consumed and they will decide on when and how to respond to it. Generally, if the dog or pet consumes 40 mg/kg body weight of theobromine from milk chocolate, decontamination is recommended. For dark chocolate, it may be closer to 20 mg/kg of body weight since dark chocolate contains more theobromine per gram. Your vet will decide which method is best, which may include inducing vomiting, using activated charcoal and Glauber’s salt, Emesis, gastric lavage, and encouraging frequent voiding of bladder.
Calculating general level of toxicity of Theobromine
Here are some general guidelines pointed out by the article referred to at the bottom of this page. Below is a rough calculation to figure out approximately how much theobromine was ingested, and how to determine if the pet should go through decontamination.
Calculate the theobromine content of the chocolate by multiplying the amount consumed with the theobromine content of that type of chocolate.
Theobromine content divided by weight of animal to determine mg of theobromine per kg of pet weight.
After the result from step 2, the value can be compared to the following:
Milk chocolate (less than 31% cocoa) If value is greater than 40 mg/kg body weight: decontamination necessary. Values below, no measures necessary
Dark chocolate (above 31% cocoa) If value is greater than 20 mg/kg body weight: decontamination necessary. Values below, no measures necessary.
Example 1:
50 lb dog consumes 50g of 72% dark chocolate.
Therefore, 50 multiplied by 12.7 (the amount of theobromine found in 70% dark chocolate) equals approximately 635 mg of theobromine consumed.
Then, 635mg divided by 22.5 (weight of dog in kg) equals 28mg/kg.
In this case, decontamination would be necessary since this is above 20 mg/kg and likely to cause illness to the dog.
Example 2:
3 kg dog consumes 15g of milk chocolate.
Therefore, 15 x 2.3 (the amount of theobromine found in milk chocolate) equals approximately 34.5 mg of theobromine consumed.
Then, 34.5mg divided by 3 equals 11.5mg/kg.
In this case, decontamination would likely not be necessary since this is far below 40 mg/kg. The dog may only show light discomfort or no symptoms at all. However, this would be something for a veterinarian to decide.
Resources
Much of the information here was gathered from Vetpharm and the references at the bottom of that article linked. The original is in German, but you can use your browser to translate it to English or your language.