Sunlight, Cats and Vitamin D

Cats always prefer the sunshine. Well, not always. If you are a black cat in hot sun, you’ll go into the shade. Humans need sunshine because we synthesise vitamin D in the skin through exposure to sunlight. In the northwest of America and in Britain, people do not get enough sunshine. This can have a negative impact on health.

Cat napping in the sun inside the home – Photo by Pak Gwei (Flickr) creative commons.

So what about cats? Cats do like to lie in the sun. We all know that. Why do they like it so much? Is it because they instinctively wish to soak up sunlight to convert it into Vitamin D?

One website says that cats convert sunlight to vitamin D, as we do. The problem that I have with this is that a cat is covered with fur. The process of sunlight shining on skin and being synthesised in the skin is not going to work unless the hair can absorb sunlight and transmit it to the skin which is far too fanciful to be believed.

The answer is that, although vitamin D (calcitriol) is an essential dietary ingredient for cats, they cannot synthesise it from sunlight. Cats obtain vitamin D from food. Caution: people should not provide vitamin D supplements if providing their cat with high quality cat food as it is possible to overdose a cat with vitamin D. At high levels it is toxic to a cat. A vet should be involved before providing vitamin D supplements.

Vitamin D is important for strong bones. A deficiency can cause rickets. However, only small amounts are required on a daily basis: 50 to 100 I.U. –  International Unit).

Cats lie in the sun for warmth. This preserves energy for other activities. When napping cats often pick out a spot in the sun. The body does not have to work as hard to maintain the correct body temperature if it is being warmed up from an external source. A radiator is just as good.

Associated post: Vitamin supplement senior cat.

Source: Drs Eldredge, Carlson, Carlson (DVMs) and Giffin MD.

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Sunlight, Cats and Vitamin D — 4 Comments

  1. Most cats, including ours, love to lie in the sun but they also know when to move into the shade for a cooling off.
    But a long time ago we had a black and white long haired cat Bert who loved the sun so much one day he got sunstroke and we had to have the vet out urgently. After that if he was too long in his favourite sunny spot I’d put him a parasol up, to the amusement of the neighbours!
    He never did learn in all of his 17 years you can have too much of a good thing lol

    • It is strange that a cat does not know when he is overdoing the sunbathing! 🙂 My you, Persians have thick, long coats and with the black fur he probably overheated very quickly.

    • That sounds like something Monty would do. He actually is smart about the sun. It’s just bees that seem to be beyond his learning curve.

  2. There is a theory that people living nearer the equator have almost no incidence of Multiple Sclerosis (MS) because they get more sunshine and synthesize more vitamin D. MS is very common in the area where I live. No one knows the cause. But the theory that it is from lack of sunlight seems plausible. Do people struck with MS have a history of lower exposure to sunlight? Is this disease affecting people who predominantly stay indoors? Can vitamin D supplements help? I have read articles stating that the recommended dose of vitamin D is actually way too low. Also, people are told to slather on sunscreen each and every time they go out. I don’t do that. I try to get some sun exposure when I can. But if I’m canoeing or working a fireworks show, then I buy sunblock. I think some sunlight is necessary for us. But too much is too much and those are the times you have to take steps to protect yourself.

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