Dear Daisy Dog:  My vitamin D level is low, so my doctor recommended I take vitamin D orally and get more sunshine, since ultraviolet light produces vitamin D through the skin.

That got me thinking about my German shepherd who has a thick, dark coat and spends much of his time indoors. Should I have his vitamin D level checked?

Daisy Responds: Sunlight stimulates human skin to produce vitamin D. However, this doesn’t occur with dogs and cats.

We pets obtain our vitamin D exclusively through our diet. Fortunately, pet foods contain adequate vitamin D, so deficiencies are rare.

Intriguingly, in a study of huskies that lived in the polar latitudes, dogs exposed to the most sunlight had the lowest vitamin D levels. As it turned out, vitamin D levels in these dogs’ blood samples correlated closely with the amounts in their food.

In another study, puppies exposed to adequate sunlight were raised without any vitamin D in their diets. They developed rickets, a disease that results from vitamin D deficiency.

So it’s clear that we dogs lack the ability to produce vitamin D from sun exposure but, instead, get what we need in our food. As long as your dog is eating a balanced diet and his veterinarian says he’s healthy, there’s no need to check his vitamin D levels.