Do Cats Need Sunlight? A Vet’s Take on the Risks & Benefits
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Do cats really need sunlight to stay healthy? You’ve probably heard that humans need sunlight in order to produce the vital nutrient, vitamin D. But is that true for cats? Let me share the medical facts with you…
Cats do not require sunlight or ultraviolet light to metabolize vitamin D. Cats with zero exposure to sunlight can stay perfectly healthy as long as they have a complete and balanced diet. On the other hand, frequent sunbathing can cause several skin diseases in cats.
In this article, I will review how cats metabolize vitamin D plus the risks and benefits of sunlight for cats. Please remember, it’s important to consult your veterinarian for specific guidance on your particular cat’s needs.
Do Cats Need Sunlight for Vitamin D Metabolism?
A vitamin is an organic compound that is essential for normal life functions. Vitamin D is one of the fat-soluble vitamins animals need to help them metabolize calcium, phosphorus and magnesium. In humans, an important source of vitamin D comes from a process that occurs in the skin when sunlight causes a conversion of vitamin D precursors.
For a long time, scientists weren’t sure how cats got their vitamin D. Some theorized that the oils on a cat’s fur somehow reacted with sunlight to form vitamin D which was then licked off by the cat. That theory was not accurate, by the way.
Over the years, researchers have devised different tests to see whether sunlight influences a cat’s blood vitamin D level. A 1999 study published in the Journal of Nutrition fed young cats a diet with zero vitamin D in it. Then they exposed some of them to ultraviolet light while others got no UV light.
The researchers found that all the kittens experienced declining vitamin D levels. They even shaved the fur off the back of some of the UV-light-exposed kittens. That made no difference. Their conclusion was that vitamin D is not produced in cat skin as a result of sun exposure.
The study also looked at the amount of vitamin D contained in cats’ traditional prey animals (mice, rats and birds). They determined the prey animals contained sufficient vitamin D to meet a cat’s needs. Other studies have confirmed these findings.
The bottom line: cats do not need sunlight for vitamin D metabolism. In fact, sunlight does nothing to raise a cat’s levels. They must get all of their vitamin D from their diet.
As far as we know, other than being a source of light that helps them interact with their environment, sunlight doesn’t have any specific role in a cat’s physiological functions.
Is Sunlight Good for Cats?
While cats have no known physical requirement for sunlight, it may provide psychological benefits. Cats habitually seek areas of natural sunlight even when it’s not next to a window.
Now, is that because they enjoy the warmth or is there some other benefit that we humans just don’t understand? We don’t know.
Until more research is done, veterinarians assume cats enjoy the feeling of warmth brought from lying in a sunny spot. No one has yet identified any essential physiological or psychological need fulfilled by sunshine.
Risks of Sun Exposure
There are several risks for cats from the sun’s rays. The risks are greater for cats living outside with access to direct sun rays, but even indoor cats can have bad reactions. Let’s go over some of the conditions caused or exacerbated by exposure to UV light.
Also known as actinic keratitis, solar dermatitis is an inflammatory condition. Ultraviolet B light rays from sunlight are absorbed by the skin and cause cell damage.
Thin-haired areas such as the nose and ears of white cats are the most susceptible. Symptoms include crusty, peeling skin and the formation of sores. Solar dermatitis can progress to skin cancer in some cases.
Sun radiation can cause the formation of hemangiomas which are benign tumors made up of blood vessel cells in or just under the skin. They often look like a purple, blue or reddish bump and can range in size from pinpoint to about half an inch in diameter. These tumors usually occur on thin-haired areas like the ear flaps and are most common in white cats.
Although hemangiomas are benign tumors, it’s impossible to tell them apart from similar cancerous tumors without a biopsy.
Squamous cell carcinoma is a type of skin cancer that may be induced by UV light exposure. These tumors usually affect the eyelids, nose and ear flaps with older, light-colored cats having a higher risk. The cancers might have the appearance of a tumor or a severe sore.
A biopsy is required to make a diagnosis. Treatment involves surgical removal, radiation therapy and/or chemotherapy. The prognosis is fair to good with early, aggressive treatment.
Pemphigus Complex is a set of immune-mediated diseases of the mucocutaneous tissue of cats. Although it’s uncommon, it can be made worse by ultraviolet light exposure. Symptoms include crusts, pustules and sores on the ears, nose and chin.
A biopsy is required to make a diagnosis in most cases. Treatment often requires corticosteroids and other immunosuppressive medications. The prognosis is fair to good with proper diagnosis and aggressive treatment.
Overheating or heat stroke can occur as a result of sun exposure in cats. Symptoms of heat stroke include a body temperature of 105.8 F or higher, respiratory distress, weakness and bluish gums. Heat stroke is more likely to occur when environmental temperatures are near or above 90 degrees F and when humidity levels are also high.
Overheating from sunbathing is not common in cats as most will move away from the sun when they start to get hot. But cats with other diseases that may alter their perception of heat could be more susceptible. Elderly cats and cats with poor mobility should be monitored closely while sunbathing to prevent overheating.
Sun Safety for Cats
The most effective step to prevent your cat from getting sun-related skin damage is to limit their time lying in the sun. If that’s not possible, here are a few more strategies to consider:
- Keep cats in the house from about 9 in the morning until 3 in the afternoon.
- Apply UV-blocking film to windows.
- Make their favorite sunbathing spot less appealing with cat-deterring devices like Ssscat compressed air or these spiky grid mats.
- Create inviting places for your cat to rest away from windows.
- Apply sunscreen with SPF 30 or higher to areas of skin that get the most sun exposure (ears, bridge of nose). DO NOT USE SUNSCREEN THAT CONTAINS ZINC as it can cause toxicity when licked by cats.
- Cats do not require sunlight to metabolize vitamin D.
- Cats must get all of their vitamin D from their diet.
- While sunlight may have psychological benefits for cats, there is no known essential physiological need fulfilled by sunshine.
- Sunlight risks for cats include solar dermatitis, skin hemangiomas, skin cancer, pemphigus complex, and heatstroke.
- To prevent sun-related skin damage in cats minimize their exposure with UV-blocking window film, sunscreen lotion and less time spent outside.
- Cannon, A. G. (2011). Actinic Dermatoses: Recognition, Diagnosis, Treatment Options & Prevention. Western Veterinary Conference 2011, Las Vegas, Nevada, United States of America.
- Chacar, F. C., Kogika, M. M., Zafalon, R. V., & Brunetto, M. A. (2020). Vitamin D metabolism and its role in mineral and bone disorders in chronic kidney disease in humans, dogs and cats. Metabolites, 10(12), 499.
- Dorn, C. R., Taylor, D. O. N., & Schneider, R. (1971). Sunlight exposure and risk of developing cutaneous and oral squamous cell carcinomas in white cats. Journal of the National Cancer Institute, 46(5), 1073-1078.
- Morris, J. G. (1999). Ineffective vitamin D synthesis in cats is reversed by an inhibitor of 7-dehydrocholestrol-Δ7-reductase. The Journal of nutrition, 129(4), 903-908.
- Parker, V. J., Rudinsky, A. J., & Chew, D. J. (2017). Vitamin D metabolism in canine and feline medicine, Journal of the American Veterinary Medical Association, 250(11), 1259-1269. Retrieved Jan 23, 2023, from https://avmajournals.avma.org/view/journals/javma/250/11/javma.250.11.1259.xml
- Rivers, J. P., Frankel, T. L., Juttla, S., & Hay, A. W. (1979). Vitamin D in the nutrition of the cat. The Proceedings of the Nutrition Society, 38(2), 36A-36A.