Why do my cats like to eat grass?

While cats need meat to survive, they do seem to love the texture and flavor of grass. "They may eat grass because it adds fiber to their diet, which helps work food through the system," says Marty Becker, DVM. "It lets them vomit indigestible contents such as hairballs from grooming and feathers, fur, and bones from eating small prey." Don't worry: Vomiting may seem repulsive to you, but it's healthy for your cat, he says.

Outdoor cats will find their own green delicacies in the wild, of course. But you can give your indoor cat the flavor of outdoor life with a tasty patch of edible grass and a bowl of water. It's easy to grow cat grass from seed in a wide, low container. Usually oats or a mix of oats, rye, barley, and wheat will attract your kitty. (You can probably find these seeds at your favorite pet store.) Add a small bowl of water to your mini landscape, too. Because your feline friend always appreciates easy ways to stay hydrated.

Overindulging on grass can cause digestive upset, so limit your cat's access to the grass if she gets too voracious.

RELATED: Just How Often Should I Really Be Feeding My Cat?

1. Fill a container approximately 12 inches wide with potting soil and sink a small bowl about 2 inches deep into the soil. Sow cat grass seed around the bowl, following the package instructions to determine the depth of the seeds.
2. Move the container out of your pet's reach to prevent digging while the seeds take hold. Keep the soil moist and warm (about 70˚F) and near a sunny window or under a plant light.
3. In 10–14 days, the grass should be tall enough to share with your cat. The water dish will draw your cat to the grass, so remember to clean and refill the water dish frequently.

Nibbling grass seems an unusual habit for carnivores like cats, but it’s surprisingly common. Here, we look at what might lie behind it, and whether owners should be worried.

Cats are ‘obligate carnivores’, which means they have to eat meat, and don’t need plant-based foods to survive. But if you’re a cat owner, you might well have seen your pet munching on long blades of grass outdoors. So, why are some cats obsessed with eating grass? And could this be a problem for their health?

Grass is a digestive aid for cats

One idea is that cats use grass as an aid for feline indigestion. They lack the enzymes needed to digest grass, and so the individual blades either pass through their systems whole, or are regurgitated. Either way, the grass may help ease stomach discomfort and allow your cat to clear any indigestible matter (such as their own hair; or fur, feathers and bones from their prey) from their system.

It’s quite common for cats to be sick after eating grass – one study found that over a quarter of cats do this. Often, it’s not true vomit, but grass regurgitated with fur, feathers or other indigestible matter. A cat eating grass and vomiting isn’t normally a cause for concern, but if your cat is sick frequently (more than once a week) or you notice blood or mucus in their vomit, or they start foaming at the mouth, take them to the vet as soon as possible.

Animal nutritionists and behaviourists aren’t sure of the exact reasons why cats eat grass, but they do have several theories…

Cats eat grass for nutrition

In the wild, cats consume small amounts of vegetable matter when they eat the stomachs of their prey. Our pet cats may not get the same nutrients in their processed cat food, so some experts think they may eat grass as a substitute. Grass juice contains folic acid, which helps support blood, immune and digestive health, as well as trace amounts of vitamins A and D and niacin.

Cats are purging parasites

Scientists have discovered that the ancient ancestors of many meat-eating mammals, including cats and primates, would eat grass to help purge worms and other parasites from their digestive systems. The grass, being high in insoluble fibre, stimulates muscle activity along the digestive tract, helping them to expel the parasites in their poo.

This theory might explain why younger cats are more likely to eat grass, as they have immature immune systems and are more prone to parasites. So, a domestic cat eating grass may be showing instinctive behaviour that’s a throwback to their wild ancestors. But this doesn’t mean the habit is a substitute for worming. Even if your cat likes to snack on greenery, make sure they have regular, vet-approved worming treatments, too.

Enjoyment!

If your cat keeps eating grass, you might notice that they seem to be really enjoying it. Some scientists have proposed that eating grass might trigger a reward response in the cat’s brain, similar to the dopamine hit that pandas get from eating bamboo. Others think the munching may help to calm them, like humans chewing gum, or ease anxiety. Or it may just taste nice!

Yes – while chewing grass may be one of our cats’ more puzzling behaviours, it’s not usually a cause for concern. One study found that almost 90% of cats who have outdoor access eat grass.

If your cat likes to chomp on the edges of your lawn, don’t use chemical weed killers or pesticides that could be poisonous to them. If your cat has taken to nibbling your neighbours’ grass, ask them to avoid harmful chemicals, too, and consider providing a pot or tray of cat grass in your home.

If your cat likes to eat their greens, it’s especially important to make sure you don’t have any toxic plants or cut flowers around your home or garden. Lilies can be fatal to cats, and other common plants, such as daffodils, amaryllis and aloe vera, can cause vomiting and diarrhoea.

Giving your indoor cat their own fresh grass will help satisfy their instinctive behaviour to chew a few blades, and may even bring health benefits (as outlined above). Broad-leafed grass varieties such as oat, rye, barley, wheat, alfalfa and cocksfoot – sometimes called ‘cat grass’ – are safe for your pet and easy to grow.

Usually it’s a harmless habit, but very rarely, a cat may get a grass seed or blade stuck in their nose or sinuses. If you notice your cat repeatedly sneezing, pawing their face, or with a runny nose or eyes after eating grass, take them to the vet to see if this could be the problem.

Your cat should also be checked out if you notice them eating much more grass than they normally do, if they vomit more than usual after eating grass, or if you suspect they may have eaten chemically treated grass. But, in general, don’t worry: eating grass is a normal habit in healthy cats.

If your kitty is snacking on grass, she could be suffering from tummy troubles, but can cats eat grass when they're feeling just fine? And why do cats eat grass in the first place?

Cats are "obligate carnivores," meaning they require a steady diet of meat to thrive. They don't need a salad with their chicken dinner, and their bodies just don't have the proper enzymes necessary for properly processing vegetation. But, can cats eat grass? The short answer is "yes." Your furry friend might enjoy crunching on some safe greens (more on that later), but choosing the right cat food that provides necessary nutrients is more important than serving up a plate of freshly-cut grass.

As it turns out, cats may munch on grass for some of the same reasons that people incorporate greens into their own diets. Some, like Animal Planet, theorize that cats eat the green stuff because it aids in the removal of non-digestible materials, like fur, assists in relieving constipation, and provides them with nutrients, like folic acid. Chewing on grass or plants also can alleviate stress, according to Vetstreet.

Digestive Needs

Although experts do not refer to grass as being necessary for cats' digestive system, reports Animal Planet, cats may seek out soft blades of grass "to settle their stomachs, much as humans pop an antacid tablet." If your cat overeats or is blocked up, her instinct is to sweep all that out with the fiber found in vegetation. Have you ever noticed your kitty chewing on the toilet paper roll? The need for fiber also motivates this behavior — she's seeking relief, not trying to waste household goods.

Cats require folic acid (vitamin B9) to aid digestion and support cell growth. Kittens get their required dose of folic acid from their mother's milk, but if a cat doesn't get enough of it, notes Animal Planet, she can develop anemia. Because folic acid is present in grass juice, some researchers speculate that cats undertake a quest for grass to supplement this deficiency, but there is no definitive evidence that they do so — and the cats themselves aren't talking. If you suspect that your furry friend is coping with a nutritional deficiency, speak with your veterinarian before trying to treat the issue on your own.

Anxiety

Similar to their pet parents, cats partake in what's called "stress eating" or "emotional eating," causing a kitty to eat not to relieve hunger pangs but to relieve anxiety or to satisfy an oral fixation. When stress hits, she needs an outlet: "A cat that constantly eats grass or plants also may be exhibiting signs of a displacement behavior," says Vetstreet. "Some cats may exhibit over-grooming or excessive vocalization when they are anxious, while other cats may try to engage in a different activity to soothe themselves, such as finding something to chew on." If you notice that your fur baby is chewing on grass or household plants excessively or shows other signs of stress or anxiety, such as withdrawing from family members and displaying aggressive behavior, get in touch with your vet to see how you can help your kitty.

What to Look For

So, why do cats eat the green stuff? Well, grass offers them relief from a variety of issues. This relief comes about most commonly in the form of hairballs, familiar to pet parents everywhere. Some cats throw up after eating because of other factors, such as changes in their diet, but if you know your cat has ingested grass, expect it to come back out again.

Because they lack the proper enzymes to digest it, cats who eat grass will then vomit that grass, along with the hair and/or other indigestible items. However, "when the fur moves deep into the digestive tract," explains PetMD, "kitty needs a little help to break it down and pass it out the other end." In other words, if the blades of grass she consumed don't come back up as hairballs, your cat will expel them in her litter box.

Prior to being wholly domesticated, cats that foraged for food in the wild (and as big cats, like lions and tigers, still do) oftentimes ingested the entirety of their prey — bones, hair, and all — which rendered vomiting a necessary part of the digestive process. Instinctively, even the most pampered kitty knows that chewing on grass will remove the problematic waste matter in her digestive system, one way or another.

Safety and Prevention

As noted above, if your cat has consumed grass, there are a few ways it will pass through her system: hairball, stool or a combination of both. If she enjoys chomping on a few blades of grass periodically and easily expels the plant matter, you needn't worry too much.

However, the Independent Ireland reports, sometimes the grass can "end up stuck at the back of the nose, inside the nasal chambers, causing fits of sneezing. This is more common in cats than dogs. When it happens, the grass needs to be physically removed." If this occurs, then contact your vet right away for safe removal.

Untreated, plain grass makes a nice salad bar for your feline friend, but if she consumes grass or other plant matter (indoor or outdoor) that has been treated with pesticides or herbicides and/or is naturally toxic to animals, it's important to seek medical attention for her right away.

Reactions to ingestion of toxic vegetation range from mild to severe, including death; therefore, it's crucial to know which grasses and plants are safe for your kitty. Keep in mind that toxic grasses, plants, and flowers, such as lilies, can be found in many popular floral bouquets. The American Society for the Prevention of Cruelty to Animals® provides a comprehensive list of toxic and non-toxic plants to cats.

The safest option is to keep your cat indoors and remove all toxic plants from your home. If your cat does explore the great outdoors, provide her with a secure collar with an ID tag.

Now that you know the answer to, "Why do cats eat grass?" you also can grow your own little patch of grass by planting wheat-berry seeds, as described by Petcha, so that your indoor kitty has her personal, safe lawn on which to graze.

Christine O'Brien

Christine O'Brien is a writer, mom, and long-time cat parent whose two Russian Blues rule the house. Her work also appears in Care.com, What to Expect, and Fit Pregnancy, where she writes about pets, pregnancy, and family life. Find and follow her on Instagram and Twitter @brovelliobrien.