
But can dogs eat pizza? What can one piece hurt? As it turns out, it can be seriously harmful. Here’s why.
Most human food is a big no-no
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Your pup looks up at you with those big, loving eyes, and you melt. All they want is the last bite of your sandwich – just one small bite, please?
Yet a veterinarian with more than a decade of experience counsels that people should not be feeding most human food to their dogs in any amount. While there are some foods (mostly fruits and veggies) that can be safely given to our four-legged friends in moderation, most – especially processed foods – are too fatty, too salty and too rich to be healthy.
People who think that just a bite here and there doesn’t hurt are typically underestimating how those nibbles add up over time and the damage that food can wreak on their pet’s health. That damage includes a variety of issues:
Obesity

First and foremost, too much people food is harmful to a dog’s weight. If you’re feeding your pooch the appropriate amount and kind of dog food, he or she is actually getting every nutrient, as well as all the vitamins and minerals it needs. Nothing extra is required! When do you give your pet something extra, they are most certainly getting superfluous calories, and they could possibly be ingesting something toxic to their bodies.
Pet obesity is a totally preventable condition, yet it ranks among the most serious and most common.
Organ Disease

Human food, fed regularly over time to your pet, can cause a whole host of illnesses and organ diseases. This includes damage to the heart, kidneys and liver, as well as their joints and bones. While many of us would do anything for our pets, and pay any price to ensure their health, consider about how the medicals bills for expensive treatments and medicines can accumulate.
Wouldn’t you rather reduce the likelihood that you will one day have to pay big bucks to your vet?
Behavioral Issues

A dog that is used to receiving people food becomes trained to expect a tasty treat every time it sees you eating. Begging is, at the least, an annoyance, but over time can become a more serious issue, especially if you have small children. Avoid inadvertently training your dog to whine, bark or even growl or snap when the humans all gather around the dinner table.
A study published by Interdisciplinary Toxicology asserts that ingestion of toxic foods by dogs and cats is overwhelmingly accidental, meaning that a majority of pet owners don’t directly feed their animals the food. Instead, it suggests that the animals are actually sneaking it or lunging at dropped food, a behavior which can be made worse by allowing them to eat human food to begin with.
You can avoid having to untrain your pet from these negative behaviors further down the road by not allowing them in the first place.
Pizza contains toxic ingredients

Remember when I mentioned the cheese, the meats and the crust – stuff that makes pizza so delicious for us humans?
All of that, and more, can do active damage to your dog’s health. Let’s break down the ingredients and why they are so harmful.
Sauce

Yes, even the simplest pizza sauce will likely pack a one-two punch of unsafe ingredients within. While tomatoes aren’t necessarily toxic to dogs in small amounts, the aromatics – onion, garlic, etc. – that flavor it most certainly are. Onion and garlic are part of the allium plant family, which also includes vegetables like leeks, shallots and scallions (green onions).
According to the authors of the aforementioned Interdisciplinary Toxicology study, the poisonous aspects of onions and garlic (and all other members of the allium family) are the sulfoxides and aliphatic sulfides. That’s as technical as I’ll get about it, but basically these toxins cause anemia – the lack or dysfunction of red blood cells in the body. While a common and treatable condition in humans, it can be fatal in dogs, even when only a very small amount has been ingested and after only a few days of displaying symptoms.
These symptoms will be different in range and degree from dog to dog, but the most common include weakness and fatigue, breathing issues and, in severe cases, blood in the urine. Worse, if left untreated dogs can slip into unconsciousness and pass away.
Meat Toppings

Ah, we’ve come to the meat of the matter. Pepperoni, sausage, bacon and chicken…all of these make for a mouth-watering bite, but these ingredients, which are usually pretty unhealthy for humans, can be even worse for our tail-wagging friends. These meats all tend to be super processed and chock full of unpronounceable chemicals.
Then there’s the grease and oils that come off the meat. They’re full of fat, fat which a dog’s body has a difficult time processing. Too much of this fatty meat over the long-term will almost certainly lead to obesity and can even lead to pancreatitis.
Cheese

There is a reason vets don’t suggest we give our dogs a dish of milk or ice cream every day: their bodies are naturally lactose intolerant and have a difficult time breaking down the enzymes in such products. This also includes cheese, naturally, and while a little bit here and there might not have much affect beyond some nastiness when they go outside to their business (or some flatulence inside), the dog who scores an entire pizza will be feeling mightily bad for a few uncomfortable days.
Crust

A friend of mine had a wonderful dog who started to look a little porky. I came to find out that part of the reason behind that was my friend’s carelessness. She wouldn’t eat the crusts of her pizza and when she’d get up and leave the room, her dog was helping itself to the crusts. Because she and her significant other got pizza fairly often, this happened a lot.
Unfortunately, not only are crusts often soaked in the grease, fat and oils from the toppings, because they are empty carbohydrates, dogs who ingest them are getting calorie bombs with no nutritional benefit. Additionally, most pizza dough contains sugar, yet another ingredient that our pups are better off avoiding.
Sodium

All of the aforementioned ingredients will likely have varying amounts of sodium present. Salt and sodium are not the same things; in fact the latter is its own separate mineral.
While it can be found naturally in some foods, the CDC reports that sodium is usually added to foods to make things taste saltier, make processed foods taste better, help foods last longer and make foods look and feel better. Worse, things don’t have to taste salty at all to have a lot of sodium present.
The University of California at San Francisco’s health department lists cured meats, processed cheese and pizza dough among its worst offenders for high-sodium foods. Do any of those sound familiar?
Surprisingly, the tomato sauce can be the most sodium-rich ingredient on the pie. Even if you’re making pizza at home, if you’re anything like me, you reach for the (probably highly processed) sauce from a jar, rather than spending hours simmering homemade.
A big sodium bomb – again, like if your dog pilfers an entire pie off the table – can actually be lethal, and bad begging habits when it comes to people food makes it more likely your dog will end up ingesting that much at once.
What to do if your dog eats pizza

For the most part, if your dog swipes a bite or even a slice, he or she will probably be okay. Monitor them for the next 24 hours and make sure they have access to plenty of water. All the ingredients might disagree with their stomach, so be prepared to let them outside as often as they need to.
Depending on the size and constitution of your dog, something closer to an entire pizza eaten could be fatal. Don’t panic. Give your veterinarian a call and let them know how much the pup ate. Include all the known ingredients in your description. This will allow the vet to plan a course of action and get you the help your dog needs in as timely a manner as possible.
If your vet is closed because it is after hours or the weekend, contact your local emergency pet hospital (if you don’t know where that is, go find out now and keep the info on your fridge!).
If you witness any worrying symptoms after the fact – remember, you know your dog best – trust your gut and don’t hesitate to reach out to your vet.
Conclusion
Pizza is one of the most popular foods around, and while we might have the best intentions when we consider allowing our pets to enjoy some, this particular meal is best left to the humans, and humans only.