Cat Drinking Milk
When it comes to special treats, it seems that cats naturally gravitate toward milk the way dogs take to bones and mice go for cheese. 

But while it’s true that many kitties love to lap up the white stuff, it turns out that they can’t always successfully digest milk without getting sick.

So we decided to get the real dish on how milk affects felines from Dr. Cailin Heinze, VMD, MS, DACVN, an assistant professor of nutrition at the Tufts Cummings School of Veterinary Medicine.

Should Cats Drink Milk?

“Cats do not gain anything nutritionally from milk that is not present in a well-balanced commercial [cat food] diet,” explains Dr. Heinze, adding that it should be treated more like a very occasional high-calorie treat than an everyday food.

“We generally recommend that cats be fed no more than 20 to 30 calories a day from unbalanced sources, such as human food items or commercial treats," adds Dr. Heinze. "Skim milk contains 83 calories per cup, while whole milk contains 149 calories per cup. Too many calories from such treats can dilute out essential nutrients from a feline’s main diet, contributing to the serious obesity problem that we are currently facing with our pet cats.”

Aren’t Most Felines Lactose Intolerant?

Standard cow milk has much more lactose and casein than many dairy-loving kitties can digest.

“Most adult mammals have at least some degree of lactose intolerance — and cats are no exception,” explains Dr. Heinze. “The amounts of lactase (the enzyme that digests lactose) that the body produces declines after weaning.”

In other words, cats’ bodies are even less equipped to handle the stuff as they stop nursing and get older. 

“Lactose is a sugar, and undigested sugars draw water into the intestine, causing diarrhea,” adds Dr. Heinze. “They are also fermented in the gut, and can cause bloating and flatulence.”

Ultimately, like humans, some cats will tolerate milk without a problem, but Dr. Heinze recommends offering safer treats, like bite-sized bits of cooked meat and fish or commercial cat treats for an equally tasty reward.

For answers to other curious questions about animals, check out our other "What’s the Deal With …" stories.

More on Vetstreet: