Why Do Cats Eat Grass?

Cats can be fickle creatures, demanding cuddles one moment, only to avoid human attention the next.

This inconsistency is also evident in their attitude to food, with these carnivores sometimes drawn to eating grass.

However, such impromptu al fresco meals are frequently followed by their cat vomiting up the green stuff, causing understandable concern for their owners.

So why do cats eat grass and is it safe for them to do so? Here's what feline experts had to say.

Why Do Cats Like To Eat Grass?

Cats are recognized as being obligate carnivores, meaning their nutritional needs are met by eating only meat, making this compulsion to consume grass all the more mysterious.

However, Rae Foreman-Worsley, a feline behavior and welfare researcher at Nottingham Trent University in the U.K., concedes that while scientists are not exactly sure why cats eat grass, "we do have a few​ theories."

VCA Animal Hospitals suggest this practice has evolved as a means of aiding digestion. A spokesperson told Newsweek: "Today's cats are sophisticated creatures, but they still possess the basic characteristics of their feral ancestors.

"In the wild cats stalk and hunt for food. After consuming their prey—often small mammals or birds—they may nibble a little grass.

"One theory is that eating grass makes the cats throw up the less digestible parts of their protein-rich meal [such as] hair, bones, or feathers."

Beautiful cream tabby cat eating fresh grass
Cats' compulsion to eat grass is certainly a strange one ,as they are obligate carnivores and do not require vegetation to thrive. Galina Sandalova/Getty Images

The International Cat Association (TICA) President Vicki Jo Harrison, agrees, adding: "An occasional episode of upset stomach isn't all that unusual in felines."

She told Newsweek: "It's one of the most common conditions that veterinarians treat. Since cats lack the proper enzymes to digest grass, cats who eat it will then vomit it along with the hair and other indigestible items."

Another theory indicates eating grass can have health benefits, due to the complex nutrients it holds.

Veterinarians the VCA said: "Grass is a source of needed trace minerals, micronutrients, and vitamins A, B, and D.

"Grass also contains folic acid which impacts the production of hemoglobin, an important component of blood oxygenation.

"Moreover, grass contains chlorophyll, which may aid minor medical problems. Chlorophyll may have helped cats deal with infection and pain before the advent of modern-day antibiotics and anti-inflammatory drugs."

TICAs Vicki Jo Harrison believes adding some greenery to your pet's diet can also help relieve constipation.

She said: "Some cats just like the taste of grass, and in small amounts, it can provide valuable fiber.

"When a cat overeats or is constipated, their instinct is to find relief by eating the fiber found in grass. Grass has plenty of fiber, which can help with constipation."

Doron Wolffberg, Founder of All About Cats, cites a recent study indicating eating grass is a strategy that can treat more than a simple upset stomach.

Researchers at the University of California, Davis, School of Veterinary Medicine conducted an online survey of more than 1,000 cat owners asking about their cats' penchant for eating grass and plants.

Wolffberg told Newsweek: "Based on the findings, the researchers hypothesized that cats don't eat grass as a way to naturally treat an upset stomach.

"Instead, the scientists believe that cats might instinctually eat grass and other plant matter to rid themselves of intestinal parasites—a behavior that has been observed in wild carnivores and primates."

Eating vegetation may trigger the digestive tract to expel unwanted parasites.

Why Do Cats Eat Grass And Throw Up?

Foreman-Worsley believes there are two distinct explanations for vomiting after eating grass, relating to cause and effect.

She said: "Despite the desire many cats have to eat grass, their digestive system ​can't fully break down the plant material. Coughing the grass back up means it doesn't sit heavy in the stomach.

"Cats may also intentionally eat grass when feeling nauseous to aid them in being sick, to remove hairballs or undigested food.

"It's perfectly normal for cats to vomit after eating grass, but if they happen to be doing this very regularly, it might be best to see a veterinarian just to check up on the overall health of your cat."

Robin Hargreaves, Senior Veterinary Advisor at Agria Pet Insurance, adds there is a third, more unfortunate explanation, for throwing up after eating grass.

He told Newsweek: "One interesting phenomenon we regularly see in summer is cats with grass lodged in the back of the nose, causing acute gagging and discomfort when eating or loss of appetite.

"They often go outside and come back a little later, suddenly swallowing/gagging/retching with various degrees of severity.

"Usually, these cats have brought most of the consumed grass back up, but a stiff blade has gone up the back of the nose over the soft palate rather than into the mouth.

"Because cats often eat the stiff and serrated blades of grass, it won't come back down, but rather ratchets itself further and further up, even sometimes emerging from the nose.

"This is so common that we can have a cat or two a week in summer requiring a general anesthetic to remove a blade from the nasopharynx."

Gray silver tabby british longhair cat sitting
The practice is too often followed by the cat vomiting its meal. Nils Jacobi/Getty Images

Do Indoor Cats Need Grass?

The consensus among cat experts agrees if the feline in your home indulges in the occasional nibble of grass, then this should not be discouraged.

Vicki Jo Harrison counsels "bringing the outdoors inside" for cats spending the majority of time indoors.

She said: "Indoor cats can benefit from the effects of eating grass. TICA suggests buying or growing grass indoor for your feline to chew for indoor cats to have their own personal and safe lawn to graze."

Foreman-Worsley concurs, although she cautions owners must take care of what plants they provide access to.

She said: "Providing extra enrichment for indoor cats is always a good idea, and cat grass is no exception. Whilst your cat may not opt to use it, it is always beneficial for cats to have lots of choice within their environment.

gray big cat eating green grass outdoors
When eaten in moderation and providing it has not been treated with any pesticides or herbicides, eating grass is completely fine for cats. Анатолий Тушенцов/Getty Images

"Indoor cat grass can be great for cats with outdoor access too, as it may help them to avoid eating grass outdoors that has been treated with chemical fertilizers or pesticides."

However, if you are providing indoor grass you must make sure they are kept away from other household plants that are toxic to cats when ingested.

The VCA suggests people will naturally have questions about feeding their cat grass and should talk to their veterinarian.

It said: "With your cat's overall medical status in mind, your veterinarian can give you sound advice on the pros and cons of adding grass to your cat's diet."

The VCA adds owners can grow their own grass at home and also chose which variety of grass they grow.

It said: "Cat grass usually refers to grass that produces cereal grains such as oat, wheat, barley, alfalfa, and rye.

"You can start with one variety or plant a couple of different grasses and assess your cat's preference."

Sarah Elliott, Cats Protection's Central Veterinary Officer, suggests some plants are better suited to hungry indoor kitties than others.

She told Newsweek: "If your cat can't go outside, a type of grass that cats particularly like is Cocksfoot which has long broad leaves so it is easy for them to bite.

"Cocksfoot grass can be grown indoors and seeds are readily available from garden centers and pet shops."

beautiful gray tabby cat walks on the
A gray tabby cat eats grass. SValeriia/Getty Images