can cats drink milk

A cat, a saucer of milk, a contented lap. It is one of the oldest images we have, printed on biscuit tins and drawn in a thousand storybooks. It is also wrong. Most adult cats should not drink cow's milk, and the classic saucer is more likely to cause a mess than a moment of bliss. Here is the truth behind the myth.

Let us start with why the picture exists at all. Cats do like the taste of milk, drawn to the fat and the richness, and historically cats around farms and dairies did lap up spilt milk and cream. So the association is not invented. Cats will drink milk given the chance. The problem is what happens next, inside a stomach the milk was never designed for.

most adult cats are lactose intolerant

Here is the biology the storybooks skipped. Kittens can digest milk, because they live on their mother's milk and produce plenty of lactase, the enzyme that breaks down the sugar in it. But as a cat grows up and stops nursing, it produces far less of that enzyme, and most adult cats lose much of their ability to digest lactose. This is normal and it is the case for the large majority of grown cats.

Give lactose to a cat that cannot digest it and the undigested sugar sits and ferments in the gut, drawing in water and feeding bacteria. The result is stomach upset, bloating, gas, and diarrhoea, usually within a few hours. So the saucer of milk that looks so cosy often ends in a very uncosy night for the cat and an unpleasant discovery for you. The cat enjoyed the taste and paid for it later, which it did not connect to the milk and you now will.

the exceptions, and they are small ones

Not every cat reacts, and tolerance varies. Some cats handle a small amount of milk with no obvious trouble, and there is no way to know your cat's threshold except by testing its stomach, which is a poor reason to offer it. A splash of milk will not poison a cat the way some foods will, so if your cat has stolen a lick, there is no cause for alarm. But not poisonous is not the same as good for it, and milk clears the first bar while failing the second.

You may have seen special cat milk sold in pet shops. These are formulated with the lactose reduced or removed, so they are gentler on a cat's stomach than cow's milk. They are safer, but they are not a health food, they are a treat, and they still add calories a cat does not need. An occasional small serving is fine for cats that enjoy it. It is not something to pour daily.

what cats actually need to drink

Water. Only water. Fresh, clean water, available at all times, is the one drink a cat genuinely needs, and many cats are naturally poor drinkers, which makes good hydration worth encouraging. Some cats prefer running water and take to a pet fountain, some like a wide bowl kept away from the food, some drink more if there are several water stations around the home. None of them need milk, and a cat filling up on milk instead of water is doing itself no favours.

So retire the saucer. It is a charming image and a bad idea. Keep the water fresh, keep the milk for your own tea, and if you must give your cat something milk-flavoured, use a proper cat milk in small amounts and treat it as the indulgence it is. The storybooks meant well. They were still wrong.

Related reading from my desk: can cats eat cheese, which fails for the same dairy reason, and can cats eat chicken, which does not.

If your cat has had milk and is bloated, gassy, or has diarrhoea, it should pass, but persistent or severe upset warrants a vet call. I am a cat with opinions, not a veterinarian.