Can Cats Eat Pesto?
Short answer
No, do not under any circumstances feed pesto to cats.
Long answer
The first thing to acknowledge is that there's no "one size fits all" when it comes to pesto. With dozens of different versions available, some containing unusual ingredients such as beetroot, cauliflower, and even cured meat, the only way to have any kind of confidence is to meticulously read the labels of any product that hasn't specifically been designed with pets in mind.
Having said that, when most people hear the word "pesto," they immediately think of the classic recipe containing olive oil, salt, pine nuts, cheese, garlic, and basil. Let's break these ingredients down one by one and see if they are safe for cats to eat.
Olive oil
There are no issues with cats consuming olive oil, per se. Just like humans, pets need a healthy amount of fat in their diet, not just for energy but for the essential fatty acids that they contain. However, excessive fat can not only lead to weight gain, but it can also lead to diarrhoea or vomiting if cats consume too much of it.
Salt
Scientists have different opinions on the safe level of salt that cats can have in their diets. Broadly speaking, though, there is a consensus that dried cat foods should contain no more than 0.2% salt. When you bear in mind that there are some pestos on the market containing up to 5.1% salt, at those kinds of levels, there's a very real risk of poisoning your cat, which, if not treated, can ultimately lead to death.
Pine nuts
While some nuts, such as macadamia, are toxic to pets, pine nuts (which are seeds) are not toxic for cats to eat in moderation. We don't really advise it, though. Their high fat content means your furry friend is likely to have problems digesting them. The other thing to bear in mind is that cats' teeth are designed for tearing, not chewing. That means they are likely to swallow pine nuts whole, which obviously poses a choking risk.
Cheese
Traditional pesto contains both Parmesan and Pecorino, and while they are not toxic to cats, many cats are sensitive to lactose. This means that cheese can cause digestion issues, which can manifest in tummy aches, constipation, or worse.
Another important point is that cats are what's called obligate carnivores, which means their digestive system deals with meat well but not dairy. Cheese, therefore, has virtually no nutritional value for them, and while giving a cat a tiny piece of cheese as an occasional treat is widely considered safe, it's best avoided in any great quantity.
Garlic
The jury is out on whether cats can eat garlic. Some animal nutritionists say it can be given in very small quantities, while others recommend never letting it pass their lips due to the gastrointestinal issues that could result. We take the belt-and-braces approach and never feed garlic to cats.
Basil
This is just about the only pesto ingredient that we feel comfortable feeding to cats, but even then, only in moderation.
Other ingredients
Many of the pesto sauces you see for sale in supermarkets contain completely different ingredients from the Pesto Genovese Consortium's official recipe. This additional complexity means each sauce should be judged on a case-by-case basis. Quite honestly, though, it's simply not worth the effort. The chances are pesto is very low down on your cat's ultimate food list, and if they've never tasted it, they'll never know what they're missing anyway. It's why, when we're asked if dogs can eat pesto, we also say it's just not worth the bother.