As someone who doesn't have kids, my dog is my family.

After working with clients from around the world for over 12+ years in my nutrition practice, a common finding that I see on testing is people are overdosing on vitamin A,  a fat soluble vitamin that is stored in the body and doesn't easily leave if you get too much. It hangs around and bogs down your liver. This happens from over-consuming dairy/liver/eggs, eating too many brightly colorful vegetables (think sweet potatoes, carrots, red peppers, etc.), topical vitamin A products like anti-aging retinol creams, and taking vitamin A containing supplements like multivitamins, prenatals and cod liver oil. Over several decades, the liver gets overloaded resulting in sluggishness and toxicity.

This phenomenon is well-documented in the literature:

"Vitamin A in high doses is a direct toxin. Excess vitamin A is stored in stellate cells in the liver and accumulation can lead to their activation and hypertrophy, excess collagen production, fibrosis and liver injury. The toxicity is dose related and can be reproduced in animal models." [1]

"The acute and chronic effects of vitamin A toxicity are well documented in the literature. Emerging evidence suggests that subtoxicity without clinical signs of toxicity may be a growing concern, because intake from preformed sources of vitamin A often exceeds the recommended dietary allowances (RDA) for adults, especially in developed countries." [3]

Once you understand the epidemic of vitamin A subtoxicity and toxicity in humans, it's easy to see how it's happening in dogs. This is because unlike humans, dogs eat the same thing every day, and these dog foods are loaded with high vitamin A foods (since when did dog diets heavy in orange vegetables and liver become so 'normal'?).

It's important to note that vitamin A toxicity is a slow burn, meaning it can take decades to show up in humans, and years to show up in dogs. This is because if you get a 'little bit too much' of something every day, not much happens in the short-term, but after years, it can push your body (or your pet's) to the tipping point and health issues result.

Signs of Vitamin A Toxicity in Dogs and Humans

In humans, vitamin A toxicity can look like:

• blurry vision or other vision changes
• osteoporosis
• swelling of the bones
• bone pain
• poor appetite
• dizziness
• nausea and vomiting
• sensitivity to sunlight
• dry, rough skin
• itchy or peeling skin
• cracked fingernails
• skin cracks at the corners of your mouth
• mouth ulcers
• yellowed skin (jaundice)
• hair loss
• respiratory infection
• confusion
• kidney damage
• headache
• irritability
• rash
• weight gain and obesity 

In dogs, I would expect the symptoms to be similar, with a heavy emphasis on skin issues being on the forefront since dogs can't tell us what's wrong.

Vitamin A Basics and Human Requirements

Vitamin A is considered by nutrition science as one of the fat-soluble vitamins along with vitamin D (actually a hormone), vitamin E, and vitamin K. Excess fat soluble vitamins like vitamin A are shuttled to tissue for storage, whereas excess water-soluble vitamins get excreted in urine.

Vitamin A is known for its role in a healthy immune system, eye health, reproduction, hormone production, as well as growth and development. Some amount of vitamin A is found in almost all foods, but the most abundant sources are usually easy to identify by their bright colors (usually red, orange and green from vitamin A carotenoids). "Eating the rainbow" has been said to be an easy way to get not only optimal nutrition, but to make sure you get an abundance of vitamin A in your diet.

Vitamin A is found in plant foods in the form of proform A carotenoids and also found in animal products (retinol - preform version). The plant version of vitamin A carotenoids requires conversion in your body to become useable vitamin A, a process that's efficiency has a genetic component, i.e. the conversion rate varies per person based on gene expression like BCMO1 (rs11645428). Animal sources like liver and egg yolks do not require conversion for use.

The RDA for humans is as follows:

• Men over age 19: 900 mcg RAE for men (equivalent to 3,000 IU)
• Women over age 19: 700 mcg RAE for women (equivalent to 2,333 IU)

Recommendations for dogs are not as straightforward (but way too high in my opinion):

• AAFCO recommendations a minimum of 5,000 IU/kg vitamin A for adult dogs and a maximum of 250,000 IU/kg (this is confusing, I know)
  • A 50-pound dog eats approximately 2-3.5 cups of food per day OR 220-385 grams per day of food (1kg =1000grams)
    • based on above, daily intake would be at a minimum of 1,100-1,925 IU per day for a 50lb dog

I reached out to Acana (a popular dog food brand), regarding their Wholesome Grains, Red Meat Recipe and they said it has a vitamin A content of 34,000 IU/kg as fed. Based on the example above, the same size dog would be getting significantly more vitamin A, 7,840-13,090 IU per day based on the same feeding. Now note this compared to the adult human recommendations above - a 50 pound dog would be getting 2-5x more vitamin A than is recommended for a human that is likely at least double-triple the dog's body weight.

If vitamin A subtoxicity is a huge problem in humans that hasn't even gained awareness, certainly no one is paying attention to in it pets!

The Sins of Dog Food

Dog food tends to get marginalized, ignored and stuffed with low quality, subpar ingredients resulting in feeding that is not evolutionarily consistent. Not to mention all the synthetic vitamins for dog 'health'.

Extremely high vitamin A foods have now become mainstays in dog food, namely liver, sweet potato, pumpkin, and carrots.

Amount of vitamin A in common very high vitamin A foods (often found in dog food):

• Beef Liver, 1 oz: 5,099 IU*
• Sweet Potato, ½ cup chopped: 10,692 IU*
• Carrots, ½ cup cubes: 9,434 IU*

*note 2,333-3,000IU is the RDA for adult males and females, since there is no official RDA for dogs

Now let's look at some popular high-end dog foods:

• Acana Whole Grains Dog Food -Beef, pork, beef meal, oat groats, whole sorghum, whole millet, pork meal, whole oats, beef fat, lamb, fish oil, ground miscanthus grass, natural pork flavor, beef liver, pork liver, pork kidney, beef tripe, beef kidney, potassium chloride, whole butternut squash, whole pumpkin, salt, taurine, choline chloride, vitamin E supplement, dried kelp, zinc proteinate, mixed tocopherols (preservative), vitamin D3 supplement, vitamin A acetate, niacin, thiamine mononitrate, riboflavin, calcium pantothenate, pyridoxine hydrochloride, folic acid, vitamin B12 supplement, dried chicory root, turmeric, sarsaparilla root, althea root, rose hips, juniper berries, citric acid (preservative), rosemary extract, dried Lactobacillus acidophilus fermentation product, dried Bifidobacterium animalis fermentation product, dried Lactobacillus casei fermentation product.
  • ACANA Wholesome Grains, Red Meat Recipe has a vitamin A content of 34,000 IU/kg as fed
• Ollie Dog Food - Beef, carrots, beef kidneys, potatoes, peas, sweet potatoes, beef livers, chickpeas, spinach, tricalcium phosphate, salmon oil, salt, taurine, zinc gluconate, vitamin E supplement, ferrous sulphate, copper amino acid chelate, manganese amino acid chelate, cholecalciferol (vitamin D3) supplement, riboflavin (vitamin B2), thiamine hydrochloride (vitamin B1), pyridoxine hydrochloride (vitamin B6), potassium iodide.
  • Ollie has not responded to my request 2 weeks ago for vitamin A levels.
• Maev Dog Food (this one had so much liver in it my dog wouldn't even touch it) -  USDA Beef, USDA Beef Liver, USDA Sweetbreads, Potato (Blanched), Green Beans, Zucchini, Peanut Butter, Kale, Blueberries, Fish Oil, Flaxseed Oil, Mineral Blend.
  • When I asked Maev for the vitamin A content per serving, they replied 'Thanks for getting back in touch. We are unable to share specific percentages as they are proprietary information. I have attached our Full Nutritional Panel for your review."

So not only are dog foods loaded with very high vitamin A foods, but some companies won't even tell you how much vitamin A is in it. It's 'proprietary information.'

Compounding the issue, most owners serve dog treats of cheese or containing cheese further stacking their vitamin A intake.

It's highly likely that dogs' livers are being overloaded with nutrition excess from vitamin A likely shortening their lifespan. Take a look at Bobi, the worlds oldest dog that lived to age 31 and ate what his humans ate.

What To Do

If you're reading this and following my logic, there's a few simple next steps.

1. Research the issue yourself. Don't automatically agree with a well-intentioned nutritional therapist that loves dogs on the internet, but dive into it yourself and come to your own conclusions. Consider researching first about vitamin A toxicity in humans and find out if you're overdosing on vitamin A in your own diet too (there is testing for this). It's so much easier to understand the issue with dogs if you first 'get' how it's happening in humans.
2. Contact your dog food company and find out how much vitamin A you're actually feeding to your dog. It may be difficult to get an answer, which is super discouraging, but be persistent!
3. If you're not happy with the health of your dog on your current food, mix it up and consider decreasing your current kibble by crowding it out with high quality human grade food that is low in plant toxins and vitamin A (I personally do this by feeding my dog roughly ¾-1 pound of ground beef per day and some grains, usually oats or rice to reduce amount of standard dog food I feed). You can also contact several dog food companies and see if you can find one that is on the lower end of the spectrum when it comes to vitamin A. (<---- if you do this, please report back and I'll add the levels of more dog food to the article)
4. If you disagree - please start a debate in the comments but please include your science and data!

I hope this helps give you some ideas about how to improve the health of yourself and your pet!

Suggested Resources

• 12 Signs of Vitamin A toxicity
• Vitamin A Detox Diet
• Is Wellness Culture Making You Sick?
• Livertox Database - Vitamin A
• Testing - Find out your Vitamin A level

PIN IT:

References:

1. https://www.ncbi.nlm.nih.gov/books/NBK548165/
2. https://www.hsph.harvard.edu/nutritionsource/vitamin-a/#:~:text=Recommended%20Amounts&text=RDA%3A%20The%20Recommended%20Dietary%20Allowance,cause%20harmful%20effects%20on%20health.
3. https://pubmed.ncbi.nlm.nih.gov/16469975/
4. https://www.aafco.org/wp-content/uploads/2023/01/Model_Bills_and_Regulations_Agenda_Midyear_2015_Final_Attachment_A.__Proposed_revisions_to_AAFCO_Nutrient_Profiles_PFC_Final_070214.pdf
5. https://ggenereux.blog/