Why does my cat eat grass?

What a big survey found

In 2019, researchers at the University of California, Davis surveyed 1,021 cat owners who watched their cats for at least three hours a day.

• 71% had seen their cat eat plants at least six times
• 11% had never seen it
• 91% of the time, the cat seemed completely normal beforehand
• About 27% of cats were said to often vomit afterward
• Young cats ate plants more often: 39% of cats under 3 did it daily, compared with 27% of cats aged 4 and older

Why cats might do it

The old idea is that cats eat grass to make themselves sick when their stomach is upset. The survey doesn’t support that, because most cats weren’t ill first and most didn’t vomit.

The researchers’ explanation is that it is an inherited behaviour. Plant material may help move things through the gut, which could have helped wild cats get rid of intestinal parasites. That is still a theory.

Keeping it safe

• Grow cat grass (oat, wheat or barley grass) indoors so your cat has a safe option.
• Keep toxic plants out of reach, especially lilies. See Are lilies dangerous for cats?
• Avoid lawns treated with weedkillers or fertiliser.
• See a vet if your cat suddenly eats a lot more plants, vomits often, or seems unwell.