Cats and Dairy: Get the Facts

WebMD discusses the facts about cats and dairy, and why substituting a saucer of milk for water may not be best for your kitten.

By Wendy C. Fries
WebMD Pet Health Feature

Reviewed by D. West Hamryka, DVM

Cats and milk: In children's stories, it always seems to be a match made in heaven. Who hasn't seen adorable illustrations of a kitten lapping at a saucer full of cream?

As with so many romances, the one between cats and dairy isn't quite what it's cracked up to be. That's because even though most cats adore a bit of milk, milk doesn't always return the affection. The main culprit is milk's lactose, which many cats have trouble digesting. The result: diarrhea or stomach upset. Not exactly romantic.

So, do cats and dairy ever get along? Can cats drink milk? To get the facts, WebMD talked to cat nutritionists and veterinarians. Here's what they said.

Cats and Dairy Fact 1: Lactose Intolerance Is the Norm

Just like people, cats can be lactose intolerant. And although we tend to think that's a problem, it's actually completely normal, says Linda P. Case, MS, adjunct assistant professor at the University of Illinois College of Veterinary Medicine and author of The Cat: Its Behavior, Nutrition, and Health. “The only time animals are exposed to lactose is when they're babies -- in their mother's milk.”

To digest lactose, a milk sugar, the human and feline digestive systems must contain the enzyme lactase. Fortunately we have plenty of this enzyme in our systems at birth, and it helps us thrive on our mother's milk. Yet, as we grow up, it's normal for people and cats to begin producing less lactase. Less lactase means a reduced ability to digest lactose. The result may eventually be lactose intolerance.

When a lactose-intolerant cat drinks milk, the undigested lactose passes through the intestinal tract, drawing water with it, say the experts at the Cornell University College of Veterinary Medicine. Bacteria in the colon also ferment the undigested sugars, producing volatile fatty acids.

Although all that activity might lead to an upset tummy and induce vomiting, the most common symptom of lactose intolerance in cats is diarrhea, usually within eight to 12 hours, says Susan G. Wynn, DVM, CVA, CVCH, an animal nutritionist in Atlanta, and co-author of the Manual of Natural Veterinary Medicine.