Why do cats eat grass? Seven reasons, one of which is correct.

Why do cats eat grass? You will find seven answers on the Internet, one of which is the correct one. People like to speculate about a feline behavior which looks a little odd at first sight but which in fact is quite normal, sensible and important to the health and welfare of your domestic cat.

Why do cats eat grass? Seven reasons, one of which is correct.
Picture in public domain modified by PoC.
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Domestic cat only occasionally eat grass. And they nearly always select thick bladed, lush grass. This is pertinent to the answer. Indoor cats without access to grass sometimes find a substitute, namely, a houseplant. Many houseplants are poisonous to cats, so cat owners should be really cautious about this [see houseplants which are safe]. Another issue is insecticides on houseplants.

Domestic cats would not eat grass unless there’s a good reason for it and the following reasons have been suggested on the Internet:

  1. Domestic cats eat grass as a laxative helping them to pass obstinate hairballs which refuse to leave their digestive system.
  2. The most common reasons given is that eating grass makes cats vomit and in doing so they vomit up hairballs.
  3. A variation on the vomiting theme is that cats eat grass to vomit to get rid of something toxic which they have ingested earlier.
  4. Another suggestion is that cats eat grass to alleviate the discomfort felt by a sore throat.
  5. A further suggestion is that eating grass helps relieve stomach irritation.
  6. And finally, a six suggestion is that domestic cats eat grass to add roughage to their diet.

The Reason Why Cats Eat Grass

The best reason, the most scientific and logical reason is that given by Dr Desmond Morris. Firstly, he says that the other six reasons don’t really stand up or “fit the facts”.

Domestic cats only eat grass occasionally and in quite small quantities. They do not digest grass but chew it and ingest the juices from largely long, fresh grass stems. Therefore, it would appear that domestic cats are seeking to ingest something that is inside the juice of grass.

Folic Acid

It is known that grasses contain folic acid. Folic acid is a vitamin and it is vital to cats. It plays a role in the production of haemoglobin. Haemoglobin carries oxygen around the blood. This brings me nicely to the snow leopard which is a beautiful wild cat living in the high country of the Himalayas.

Snow Leopard

This glorious animal likes to eat far more vegetation than your average wild or domestic cat. My theory is that the snow leopard eats a relatively high quantity of vegetation to increase the production of haemoglobin which in turn makes the transportation of oxygen in their bloodstream more efficient. This is something that is required in an animal living in the rarefied air of the Himalayas.


Folic acid is an essential chemical which is apparently missing from pure meat diets and so cats have to supplement their diet with eating grass. I will presume, at this stage that folic acid is incorporated as an ingredient into standard commercially prepared cat food. Accordingly, a cat fed on high quality commercially prepared food will not need to supplement their diet by eating grass.

However, the desire to do so must be inherited from their wild cat ancestor living as it does on a purely meat diet. Although, I have to note that the prey of animals often contains vegetation in their gut and therefore I would have thought that the African wild cat would automatically ingest folic acid. Perhaps domestic cats who seek out folic acid in grass are those that are fed a non-standard commercially manufactured food.

Deficiency in Folic Acid

As an aside, a cat whose diet is deficient in folic acid may become anaemic and its growth will suffer. This may be a problem with indoor cats without access to a garden. Cat owners can provide a tray of grasses as a substitute. These grasses should not be treated with weedkillers or other chemicals because they may be poisonous to cats.

Indoor Cats

The dangers of chemical treatments is the same for indoor/outdoor cats with access to a back yard/garden or communal areas. Often in these places management treat the lawn with chemicals to improve its appearance. These chemicals are likely to be poisonous to cats. Cat owners should be aware of this.

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