Why Do Cats Eat Grass?

Cats eat grass because it's a good source of certain nutrients, may help their digestive system, and simply because they enjoy it. (Ethan Weil)
Cats eat grass because it’s a good source of certain nutrients, may help their digestive system, and simply because they enjoy it. (Ethan Weil)

Why do cats eat grass? The answer is that it offers some health benefits. Cats are obligate carnivores, which simply means they need to eat meat to satisfy their nutritional needs, yet wild cats naturally ingest some grass with prey. Both wild cats (e.g., bobcats, lions, and tigers) as well as domestic cats like to snack on grass. Most experts say a domestic cat can live a long and healthy life without ever nibbling on the lawn, but if Fluffy has a green tongue, there’s no harm indulging her.

Grass Helps Clean the Gut

Cats can’t digest grass, so more often than not, nibbling on it leads to vomiting. Puking isn’t something cats do for fun. If you’ve ever watched a cat yak up a hairball, you can see it isn’t enjoyable, yet the cat appears visibly relieved when it’s over. Vomiting helps cats rid their digestive tract of fur, parasites, feathers, bones and other debris that could ultimately harm them if it wasn’t ejected. In a house cat, it’s a natural hairball remedy. In an outdoor hunting cat, eating grass may help prevent serious medical issues.

Not all of the grass is lost to vomit. Grass also acts as a natural emetic, helping to clean out the lower digestive tract. Here too, the action helps clear parasites and undigested hair, plus it prevents constipation.

Chomping grass also acts as a sort of kitty dental floss.

It’s Instinctive

A parasite-free, well-groomed indoor cat may still enjoy nibbling leafy greens, even though her vomit might only consist of undigested grass. She likes to eat grass because it’s instinctive. Veterinarian Benjamin Hart at the University of California-Davis has studied green-eating in omnivorous chimpanzees and carnivorous felines. He believes eating plants may have conferred a survival advantage in house cat ancestors, helping them expel parasites and absorb trace nutrients. Domesticated cats still retain many wild behaviors and many venture outdoors, so salad-snacking persists. Even cats that don’t eat grass tend to bat at it, since it’s basically a natural cat toy.

Cat-Friendly Nutrients in Grass

Cats can’t digest grass, but crushing it releases some of the vitamins and minerals found in plant cells. Grass juice contains folic acid, which is essential for nervous system development in kittens and red blood cell production in adult cats. A slightly anemic may seek out grass to help replenish the nutrient. Grass and flea season go hand-in-hand, after all.

Other nutrients in grass juice that may benefit cats include chlorophyll and trace amounts of vitamins A and D. More research is needed to determine the value of grass in supplying these compounds in felines.

Grass, like other green plants, consists mostly of water. Some cats get most of their water from their food. A cat fed only dry food may be slightly dehydrated. Nibbling on dewy grass may help hydration levels.

Planting Grass for Your Cat

If you cat eats grass, you can let her munch on your (untreated) lawn, but you should be aware there’s a risk your cat could get worms. Nematodes (roundworms) naturally occur in soil and can be found on damp grass.

A safer way to satisfy kitty’s green tooth is to plant grass indoors. Pet stores sell pre-sprouted wheat grass and oat seeds. Another option is to soak bird seed and allow it to sprout.

Cats may also eat fresh or dried catnip. Catnip contains chlorophyll and some of the other nutrients in grass, but it doesn’t usually cause vomiting.

When to Visit the Vet

Cats tend to instinctively avoid broad leaf plants, with the exception of catnip, but sometimes they will bite into toxic greens. Plants of the lily family are particularly dangerous because they tend to have narrow, grass-like leaves, and are deadly to cats.

If you catch your kitty nipping on any non-grass, non-catnip plant, grab a sample for identification and immediately call the veterinarian. Similarly, get your pet checked if she eats grass you suspect has been treated with lawn chemicals. Many of them are extremely dangerous if ingested.

Sometimes cats eat too much grass or are eating it to address an underlying health issue. If a cat gets diarrhea from eating grass, it’s a good idea to get a professional opinion.