Vitamin D is a crucial vitamin that plays a vital role in the health of a dog's bones. It works closely with calcium and phosphorus to keep their bones strong and functioning well. Many mammals can produce vitamin D3 in their skin when exposed to sunlight. However, dogs have lost this ability over time due to their carnivorous diet.

Unlike some animals that can soak up sunlight and convert it into vitamin D, dogs rely on their diet to get the vitamin D they need. Since dogs are natural carnivores, they get their phosphorus from muscle meat and calcium from bones, both rich sources of these essential minerals.

Vitamin D, calcium, and phosphorus balance are crucial for a dog's bone health. It helps absorb calcium and phosphorus from their food, ensuring these minerals get properly deposited in their bones, making them strong and resilient.

Calcium, phosphorus, and vitamin D are intricately linked to the dog's overall well-being, especially bone health. Due to the complex interrelationships between these three nutrients, it is rare for a dog to develop a simple deficiency or excess of one of these nutrients. One imbalance causes a cascading imbalance of two or even all three nutrients.

Calcium aids Vitamin D absorption. Calcitriol (converted vitamin D) stabilizes calcium levels with the parathyroid hormone. A vitamin D deficiency can cause the weakening of your dog's bones. Furthermore, a deficiency increases your dog's chance of fractures or broken bones.

Vitamin D has been discovered to play a role in preventing tumor growth and cell differentiation. Increased sun exposure and vitamin D levels in the blood have been linked to controlling many human cancers.

Vitamin D receptors are found in your dog's immune cells, and it has been shown that vitamin D reduces excessive inflammatory responses, which are at the basis of many chronic diseases and autoimmune disorders, including arthritis and irritable bowel syndrome.

A few critical essential vitamins are commonly deficient in raw diets and require whole foods to fulfill recommended intakes. Vitamin D and Vitamin E are two vitamins that are frequently deficient in raw diets. 

A Vitamin D supplement is usually not required when specific types of fatty fish are fed. However, two commonly used raw feeding methods, Prey Model Raw (PMR) and Biological Appropriate Raw Food (BARF), do not include raw fish, or some dog parents prefer not to feed their dogs. In those circumstances, a supplement to deliver adequate quantities of Vitamin D in the diet is indicated.

Any dog can suffer from a vitamin D deficiency if its diet is deficient in vitamin D. However, older dogs, dogs with poor digestive health, spayed and neutered dogs, and dogs on corticosteroids, antacids, or anti-seizure drugs are more prone to vitamin D deficiency than others.

Because dogs cannot produce vitamin D from sunlight like people, they must obtain it through their diet. Unless your meat is from grass-fed animals or you feed pastured eggs, you must provide other whole food sources or supplements. However, if you feed a pre-made raw diet, some already include vitamin D (or D3).

Whole foods that provide Vitamin D include:

Small fatty fish - sardines, anchovies, smelt, capelin, and herring

Salmon should be fed in moderation due to potentially toxic levels of heavy metals.

It has been estimated that more than 70% of all dogs are deficient in vitamin D! Vitamin D deficiency can lead to:

Clinical signs of vitamin D deficiency include:

Weak and pliable bones can result in folding fractures where the bones collapse onto themselves.

To read more about vitamin deficiencies in dogs, see our signs of vitamin deficiency  article here . 

Toxicity is Not Uncommon But Can Be Fatal

Your dog's skin can regulate vitamin D conversion. It can store pre-vitamin D for future usage and destroy quantities too high for the body to store. As a result, toxicity is uncommon. However, are three ways that your dog can consume toxic levels of vitamin D; pet food containing too much vitamin D, accidental consumption of a human vitamin D supplement, and unintentional consumption of cholecalciferol rodenticides, such as Rampage®, Quintox®, D-Con®, and Rat-B-Gone®.

There have been two recently documented incidents where excessive vitamin D levels were discovered in commercial dog foods. In January 2019, Hill's Pet Nutrition recalled over 25 products due to excess vitamin D levels in the vitamin pre-mix that they used to meet the AAFCO requirements for vitamins.

In February 2023, Nestlé Purina PetCare Company had to voluntarily recall select lots of Purina Pro Plan Veterinary Diets EL Elemental (PPVD EL) prescription dry dog food for excessive vitamin D levels, most likely for the same reason as the Hill’s recall. Unfortunately, these recalls do not occur until there have been many reported cases of dogs becoming ill or dying from the food.

Rodenticides that contain cholecalciferol, or activated vitamin D3, have increased in popularity since the new regulations of the use of anticoagulants in mouse and rat poisons.  Clinical signs of vitamin D toxicity from rodenticides occur quickly, within 24-48 hours, after your dog consumes the poison. Ingestion of these products can cause life-threatening increases in calcium and phosphorus levels in the body, leading to sudden-onset kidney failure. 

If you suspect your dog has eaten rat poison, take her to the veterinarian immediately. Clinical signs may not be apparent for 24-48 hours, but the damage that has occurred in those hours can be permanent.

Clinical signs of vitamin D toxicity in dogs include:

Vitamin D and vitamin A compete for each other’s function. If too much vitamin A is present in your dog’s diet, it will impair the absorption of vitamin D. Both vitamins are essential for your dog’s health but must be balanced to avoid a vitamin D deficiency. 

The AAFCO daily dietary allowance for vitamin D is 500 IU/kg of dry matter for dogs for all life stages. For vitamin A, the recommended allowance is 5,000 IU/kg of dry matter for dogs for all life stages. For raw feeders, bioavailability will be much higher. You should monitor your dog for clinical signs of deficiency or toxicity of both vitamins and have bloodwork, and a veterinary examination done at least annually.

Coconut oil is high in medium-chain triglyceride (MCT) saturated fats, which makes it an ideal partner for fat-soluble vitamins. Adding one teaspoon per 25 pounds of body weight to your dog’s meal will enhance her vitamin D levels by increasing its bioavailability. This will allow the maximum amount of vitamin D to be absorbed into the body. 

Calcium, phosphorus, and vitamin D are intricately linked to the dog's overall well-being, especially bone health. 

Vitamins A and D must be balanced appropriately for proper vitamin D absorption.

Although uncommon, vitamin D toxicity can be lethal due to kidney failure.

Natural vitamin D content in animal products 

Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease 

Vitamin D deficiency and depression in adults: systematic review and meta-analysis 

An Evaluation of the Vitamin D3 Content in Fish: Is the Vitamin D Content Adequate to Satisfy the Dietary Requirement for Vitamin D? 

Vitamin D: Production, Metabolism and Mechanisms of Action - Endotext - NCBI Bookshelf 

Cod Liver Oil, Vitamin A Toxicity, Frequent Respiratory Infections, and the Vitamin D Deficiency Epidemic 

The Role of Vitamin D in Small Animal Bone Metabolism - PMC  

Some foods naturally provide both vitamins. Cod liver oil, for example, can be a concentrated source of vitamins A and D, while liver is particularly rich in vitamin A and may also contribute some vitamin D depending on the species and source. This makes it important to consider the entire recipe rather than adding individual nutrient-rich foods or supplements without accounting for what the diet already provides.

Vitamin D for Raw Feeders

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