Dried Whey

Dried whey is the dried liquid part of milk that remains after cheese is made, and some cat foods add it for flavor and protein. Cornell Feline Health Center notes that many cats are lactose-intolerant and can have digestive problems when fed dairy products. The amount in dry food is small. For a cat with a sensitive stomach, a dairy allergy or another medical condition, ask your veterinarian.

Source: vet.cornell.edu

Whey is added mainly for flavor, and it also brings some protein. Whey protein is a high quality protein that is easily digested. In dry cat food it is usually a minor ingredient that makes kibble more appealing rather than a main protein source. It is a dairy product, so it also carries some milk sugar.

Yes, dried whey contains lactose, the sugar found in milk. Most adult cats make little lactase, the enzyme that digests lactose. Cornell Feline Health Center says many cats are lactose-intolerant and can develop gastrointestinal problems if fed dairy products. How much lactose a cat gets depends on how much whey is in the recipe.

Source: vet.cornell.edu

Whey protein itself is a high quality protein that is easily digested, which is why it is used in many foods. The part of whey that can cause trouble for cats is the lactose, not the protein. Dried whey on a label is not the same as a purified whey protein, so it still contains milk sugar along with the protein.

Pettings gives dried whey 2 out of 5 and lists it under dairy. It appears on 9 of the 149 dry cat foods we list. The score reflects that whey is mostly a flavor ingredient and contains lactose. Each food's page shows how it scores overall.