Most cats are picky eaters, but that doesn’t mean they always know what’s best for them. For this reason, every feline owner should be careful about which foods they can feed to their furry companion.

Bored Panda reached out to Molly DeVoss, a certified feline behavior specialist who runs the non-profit consultancy Cat Behavior Solutions, which is dedicated to reducing cat shelter surrenders by correcting and preventing behavior issues in the home. Molly said that proper nutrition for cats is absolutely vital, and without it, “you may notice your cat is gaining weight, having dental problems, their fur is dry, flaky, or greasy, and much more.”

Moreover, “Diseases such as arthritis and diabetes can also be a result of poor nutrition.” Molly also said that cats are obligate carnivores, which means that “they cannot survive off a diet of fruits, vegetables, and grains; they must have meat, organs, and bone.”

In the wild, a cat will consume carbohydrates from their prey’s stomach contents. However, when it comes to cat food with added carbohydrates, they aren’t generally easily digestible.

Molly said she recommends avoiding six ingredients in commercial cat foods: “by-products of any kind, meat and bone meal, corn, wheat, gluten, and soy.” It turns out that the by-products are slaughterhouse waste; what’s left of an animal after the parts for human consumption are removed.

“This can contain organs, which cats need; however, it can also contain feed, beaks, brains, undeveloped eggs, pieces of tumors, diseased organs, and intestines (sometimes with feces).” Molly warned that “While these do provide some protein content, they are not providing your cat with the taurine-rich meat he needs.”

The feline behaviorist also warned that “meat and bone meal can in fact contain roadkill, dead zoo animals, dead livestock, and even euthanized horses and pets—which can still have poison in their bodies.”

In other cases, corn, wheat, and soy are used as cat food fillers (as well as barley, oatmeal, and white rice), which are much less expensive than meat. However, Molly said that “these fillers are some of the leading causes of cat allergies. Corn, which is not appropriate for a carnivore, is an incomplete protein, contains gluten, and is one of the more allergenic ingredients.”

Molly also said that some cats may have greater tolerance towards these ingredients and lesser allergic reactions, but it doesn’t mean they’re safe. “A good-quality cat food will not contain those six ingredients; it might contain a small amount of veggies and fruit, but should be mostly meat,” she concluded.