What vitamin D supplements do you recommend for dogs?
I believe animals should get their nutrients, especially vitamins and minerals, from “real” food. Many animals only eat commercially prepared, processed pet foods. Vitamin D is a fat-soluble vitamin and, in nature, dogs would get vitamin D from the fat stores of their prey. So, instead of giving a pet a supplement that is a synthetic form of vitamin D3, I think it is a great idea to get some fresh, vitamin D-rich foods into the pet’s diet. Foods that are good sources of vitamin D include salmon, liver, eggs, yogurt, kefir, and cheese. It is less likely that you will over-supplement the animal if you give it a food source of vitamin D, rather than cholecalciferol (a high-dose, synthetic vitamin form of vitamin D).
The Tufts study discussed in part 1 of the post is evidence that food sources of vitamin D can be very beneficial. The study indicates that “dogs receiving salmon oil as a supplement had significantly higher serum 25(OH)D (on average a 19.6 ng/mL increase) than those not receiving a supplement”.1
If an animal with insufficient vitamin D levels does not have adequate vitamin D levels after trying food sources of vitamin D, I think it’s worth looking at digestion and then at a synthetic vitamin D supplement. Veterinary Diagnostics Institute (VDI) recommends a conservative amount of synthetic vitamin D to bring an animal into the sufficient range.
What dosage is recommended for most dogs?
I do not recommend that people provide synthetic vitamin D3 (cholecalciferol) supplements to their pet until they have the dog’s serum levels checked. Dosing of vitamin D should depend on serum level. Once the serum level of vitamin D is known, a veterinarian may recommend the appropriate amount of vitamin D to bring the pet to sufficient levels.
Can you over-supplement a dog’s diet with cod liver oil or a vitamin D supplement?
It is definitely possible to over-supplement a pet with synthetic vitamin D supplements. You need to take into consideration how much D3 is present in the diet already, how much D3 is in the supplement, and how effectively the supplement is absorbed. Symptoms of vitamin D toxicity can include excessive drooling, vomiting, diarrhea, dark or tarry stools, loss of appetite, increased thirst and urination, abdominal pain, weakness, depression, muscle tremors, and seizures.
Cod liver oil contains higher amounts of vitamin D than some other foods. Some veterinarians recommend cod liver oil and others do not. Cod liver oil is controversial because some believe that it can contribute to vitamin D toxicity if given in large enough amounts. Cod liver oil is also a source of vitamin A that may cause toxicity if given to the pet in high amounts. Remember that commercial pet foods contain synthetic forms of both vitamin A and vitamin D and the effects can be additive. Salmon oil may be a more utilizable source than other fish oils according to the previously mentioned study.
The best advice that I can offer is to work with a veterinarian on diet and vitamin D supplementation for pets. Veterinarians can check a dog’s blood serum vitamin D levels on at least an annual basis and anytime the dog’s health status changes.