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Vitamin A is essential for your dog’s health and well-being, playing a leading role in the maintenance of healthy skin, eyes, and immune system - known for the repair and regeneration of cells especially those that line the gut, lungs, and eye, along with skin itself.
What is vitamin A
Vitamin A is a fat soluble vitamin found in animal and plant (carotenoids) foods that is essential for life. Vitamin A itself does not occur in plants, but its precursors, carotenoids, do. In animal products, such as liver, vitamin A is highly bioavailable and accessible for your dog.
What vitamin A does for our dogs
Vitamin A for dogs' skin and beyond...
Vitamin A is widely known for skin health but also supports your dog’s healthy eyesight and immune system - especially the gut! Deficiencies in vitamin A can cause a range of serious issues from eye disturbances to immune dysfunction, and even result in death.
Because vitamin A is so important for cell proliferation and cellular differentiation, vitamin A plays a major role in development in your dog's body. We count on vitamin A to keep eyes moist and functioning and skin smooth.
What makes vitamin A so key to gut health
There is something called the gut associated lymphoid tissue. Here is where the immune system does “training” to be successful in protecting your dog from disease and environmental toxins. The gut is constantly exposed to the environment and a healthy gut is careful about what can enter the body.
When particles make their way to the intestinal barrier, the immune system must respond appropriately. Vitamin A is needed to make retinoic acid- which is essential for this response. This is where the immune system “trains” to identify which things require an immune response and act as gatekeeper to respond protectively.
How vitamin A helps with adverse food reactions
Adverse food reactions are quite common in the dog world. Vitamin A is essential for your dog's immune system to properly train and recognize things that are harmful and which things are not (such as sorting food antigens/potential allergens). Growing dogs (and adult dogs, too) should be provided with adequate vitamin A from high-quality sources to fuel this vital function.
Animal vs plant sources for vitamin A
While dogs can get vitamin A from plant foods- like sweet potato- the body has to work a bit harder to convert provitamin A to active vitamin A. Any disturbance in this process can result in sub-optimal vitamin A status.
However, beta-carotene (provitamin A) from plants is still beneficial! Independent from its function as a precursor; it has been shown to function as an anticarcinogen and antimutagen (decreases or even removes the mutagenic effects of potentially harmful chemicals). Like vitamin C and vitamin E, vitamin A also protects against free radicals. So don’t skip the liver or the orange and green veggies!
What happens with an excess of vitamin A
Too much vitamin A is relatively rare in North America, but toxicosis can include joint pain and requires a carefully managed diet. That being said - vitamin A and vitamin D work synergistically.
Interactions to note - Vitamin A, Vitamin D, and also zinc
It's good to note that excess vitamin A can hurt vitamin D status and excess vitamin D can hurt vitamin A. It is best to provide these vitamins in balanced amounts - making sure both are at optimal levels in the diet. Very often in dog nutrition, vitamin D is missing or low in homemade diets unless oily fish and eggs are fed regularly.
Something else that is good to know- zinc is required for the metabolism of vitamin A. Zinc can often be low in homemade diets as well. It is essential that adequate zinc, D, and A be provided in the diet.
Where to find vitamin A in food:
Liver, cod liver oil, sweet potato, pumpkin, leafy greens
Liver is the richest source of vitamin A. Chicken, beef, duck, turkey, etc... all contain varying amounts of vitamin A. As mentioned above, orange plants and leafy greens provide provitamin A- but your dog's digestive system has to work harder to make it into active vitamin A.
Of course, there are some instances where a dog cannot have liver in his/her diet. In those instances, cod liver oil (NOT fortified) can provide an excellent source of both vitamin A and Vitamin D.
In a homemade diet, these two options will provide all the vitamin A your dog needs.
How to add vitamin A to commercial foods with toppers:
Pumpkin, sweet potato, leafy greens, & CAREFULLY dosed liver or cod liver oil
Properly formulated commercial dog food should have enough vitamin A, so adding more can be dangerous. However, because there are beneficial compounds in liver (and cod liver oil), some can be added to kibble in very small amounts.
Vitamin A from plant foods is absolutely beneficial - especially if you are feeding kibble because kibbles are a poor source of antioxidants. Leafy greens, cooked pumpkin, and cooked sweet potato (higher calories) are great sources of vitamin A.
How much vitamin A does your dog need?
Discovering how much vitamin A is needed as a starting point can be done by getting your dog’s metabolic weight. Not sure of your dog's metabolic weight?
Your dog’s metabolic weight is his/her weight in kilograms (1 lb = 0.454 kg) raised to the power of 0.75. (kg^0.75). Then you multiply the metabolic weight by the recommended allowance of 50 for vitamin A.
Takeaways to remember on vitamin A
- Cod liver oil, liver provide bioavailable vitamin A that are excellent sources in proper amounts; in high amounts, these sources are toxic.
- Plants contain provitamin A which dogs can convert to an active form; vitamin A toxicity is not the issue that it is with animal-based vitamin A. Plant-based A would not be appropriate for puppies as the sole source of vitamin A.
- Beta-carotene (plant-source vitamin A) serves beneficial functions outside of vitamin A and is a great addition to nearly all diets.
- Vitamin A status can be affected by sub-optimal zinc, excess vitamin D, underfed dogs in general, sub-optimal fat intake, and poorly digested commercial foods.
Steps to evaluate vitamin A in your dog's diet
- Identify vitamin A and the form of it in your dog's current diet.
- Is the vitamin A in your dog's diet a good source? Is it plant based? Animal based?
- Any provitamin A present in both the commercial or homemade diet?
- If adding fish oil- did you accidentally select cod liver oil when vitamin A and D was not needed?
- How much is in the diet?
(Applicable for homemade diets and some commercial whole food diets that provide ingredient amounts, while also taking into consideration your dog's current body weight, target weight, age, and energy level.)
Vitamin A is essential for your dog's health, and it can make all the difference in keeping your dog's eyes, skin, immune system and gut healthy. Be sure to consult a trusted veterinarian or pet nutritionist if you're giving vitamin supplements to ensure that your pup gets vitamin A in an optimal bioavailable and accessible form.
You can also listen as I talk through all this information on vitamin A and your dog in the accompanying audio below. (EDIT NOTE FOR AUDIO: Itchy dog AND disturbance to stools/digestion is common in immunologic adverse food reactions; appropriate vitamin A in the diet is helpful with both issues.)
Next up in the Basic Nutrition Channel on Dogly
Now that you have a good understanding of vitamin A, continue to the next essential vitamin step-by-step guide on vitamin D.
Or hop over to the Basic Nutrition Channel if you'd like to ask a question in the Community discussion and start any of the other step-by-step guides in Needed Nutrients. If you ever need more personalized nutrition guidance, please reach out!
- NRC Nutrient Requirements of Dogs and Cats 2006
- DSM (link above)
- Canine and Feline Nutrition (Awesome textbook)
- Chris Masterjohn, PhD- varying podcasts