Also called · retinol · beta-carotene · carrot
What it is
Vitamin A is a fat-soluble vitamin involved in vision, maintenance of epithelium and immune function. Its active form is retinol.
Plants contain no retinol. They contain a precursor, β-carotene, which humans and dogs convert into retinol internally. That is where the idea that carrots are good for the eyes comes from.
Cats cannot make that conversion. They lack activity in the intestinal enzyme that cleaves β-carotene, so no amount of carrot or pumpkin becomes vitamin A. It is one of the grounds for classifying the cat as an obligate carnivore.
A cat therefore has to eat preformed retinol from animal sources — liver and fish oil among them. Cat food has it added separately.
What it does
Why a vegetarian diet does not work for a cat
Vitamin A is not the only one. Taurine, arachidonic acid and niacin stack up alongside it as things a cat cannot make for itself. A diet built from plant ingredients alone does not hold together for a cat.
A shortage shows in the eyes and skin first
Night blindness, dry cornea, and abnormal keratinisation of skin and mucous membranes are documented. It is rare in an animal fed a complete diet.
How to feed it
If you are feeding a complete cat food, no supplementation is needed. The problem arises with home-cooked and vegetarian diets.
The principle is to meet it daily through the main diet.
What to watch for
It is fat-soluble, so it accumulates. Liver is extremely high in retinol, and giving it often as a treat causes hypervitaminosis. In cats this is known to produce deforming spondylosis — bone overgrowth on the cervical vertebrae that leaves the animal unable to turn its neck.
Some dog foods are formulated on the assumption of β-carotene conversion, which can leave a cat short of retinol. Taurine and arachidonic acid come up short at the same time.
Common questions
It does no harm. It is simply meaningless as a source of vitamin A — it adds calories and nothing else.
We would not suggest it. Being fat-soluble it accumulates, and excess is harder to reverse than deficiency.
Concerns this ingredient relates to
General nutrition information. It does not replace a diagnosis or a prescription. If your animal has a medical condition or is on medication, talk to your veterinarian first.