Just as in humans, vitamin D levels were set to prevent rickets in animal feeds, there is not enough to prevent other vitamin D deficiency issues like cancer.

In addition animals need sun exposure to convert cholesterol to vitamin D. Our dogs lifestyles have changed immensely in the past 50 years. They went from outdoor, backyard animals to indoor pampered poooches. Their ability to make vitamin D by sun shining on them is greatly reduced.

Cornell Universtiy is now looking into vitamin D for treating cancer in dogs.

“Calcitriol for Treatment of Mast Cell Tumors in Dogs. Calcitriol (vitamin D) inhibits the growth and progression of many types of tumors. Our preliminary data suggests calcitriol might be an effective treatment for dogs with mast cell tumors. The purpose of the study is to treat dogs with measurable mast tumors with calcitriol and evaluate tumor response. Dogs that have received prior prednisone or chemotherapy are eligible. Dogs entering this study will have a pre-treatment biopsy and pharmacokinetic samples collected after the first calcitriol dose. There is full funding for this clinical trial. For more information, contact Dr. Kenneth Rassnick at kmr32@cornell.edu.”

Only a vet can calculate the proper amount of vitamin D for a dog. It entails their weight, the vitamin D content in their food, and the caloric content of the food. Too much vitmain D is just as bad as too little.

The whole story is not in yet, but the data suggests changes will be coming in how much vitamin D is put into dog food.