Vitamin A toxicity (also called Hypervitaminosis A) might be one of the reasons eating "too healthily" might actually make you sick.
Do any of these signs of vitamin A toxicity sound familiar to you?
- blurry vision or other vision changes
- swelling of the bones
- bone pain
- poor appetite
- 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
- kidney damage
What is Vitamin A?
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.
How Vitamin A Toxicity Can Occur
It's not unlikely for a client to say to me, "I eat healthier than everyone I know, but I'm also the sickest." I'm now suspicious that vitamin A toxicity or excess may be a part of the problem.
Vitamin A has been long touted as a nutritional superstar, although its found in almost all foods but most abundantly in a whole foods diet. By policy, it was added to low-fat milk products in 1970's. It's also found in multivitamins, supplements (cod liver oil is a big one here), skin creams (especially anti-aging creams), sunscreen, pharmaceutical drugs (like Accutane and Tretinoin), and increases in the body if you're on the birth control pill. Depending on your health history of the above, vitamin A toxicity or excess may impact you, perhaps at much lower dosage levels than reported in scientific literature.
Vitamin A in Common Health Foods
I know what some of you are thinking, "but vitamin A is important for hormonal balance, thyroid health, and fertility." But let me show you how easy it can be to get too much, especially considering once "seasonal foods" are often now available year-round. Here's an example of some commonly eaten "health foods" that are high in vitamin A (retinol):
- Liver 338% DV in 100grams
- Salmon 25% DV in 100grams
- Butter 11% DV in 1 tablespoon
- Cheddar Cheese 12% in 2 ounces
- Eggs 24% DV in 3 hard-boiled eggs
- Fortified cereal — up to 60% in 1 cup
Then we have proform vitamin A called (beta carotene) that is not hard to find in plants. Examples include:
- Sweet potatoes 769% DV in 1 cup
- Carrot 44% DV in 1 medium
- Kale 206% DV in 1 cup, chopped
Do you see how one could easily get the daily value of vitamin A through eggs, a few tablespoons of butter, and a carrot or two?
Then layer on a multivitamin and possibly other supplementation containing vitamin A (like cod liver oil) that doubles or triples what they are already getting from food? Then they also might have a history of using the birth control pill (which increases vitamin A), use of vitamin A containing prescription drugs, sunscreens with added vitamin A and beauty creams (like tretinoin cream in 'skin cycling' routines) that puts their intake way over the top.
To stack the deck even further are organ meat supplements. Organ meats are wildly growing in popularity these days as a great way to get real food nutrition with liver specifically is one of the richest sources of vitamin A available.
Getting Too Much
If you're following along with me here, you can see the probability for someone aggressively seeking "health" to accidentally overdose on vitamin A is actually quite likely if supplements are involved. It quickly becomes a game of getting too much (not too little).
Hypervitaminosis A, or vitamin A toxicity is well documented in the literature, but science claims this only happens through long-term use of dosages significantly beyond the Tolerable Upper Intake Level of 10,000 IU of vitamin per day for adults. Common examples given for documented toxicity are usually well over 40,000 IU of vitamin A per day.
According to a 2006 study:
"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. Osteoporosis and hip fracture are associated with preformed vitamin A intakes that are only twice the current RDA."
A 2018 study that looked at cadaver liver samples (liver biopsy is the gold standard of assessing vitamin A toxicity, but it is too expensive and invasive to be used on the living) found that 33% (9 out of 27 liver samples) had hypervitaminotic concentrations of vitamin A. Only 22% of samples (6 out of 27) were found to be vitamin A deficient, supporting the premise that vitamin A toxicity is more prevalent than deficiency.
Certain groups of people should be extra cautious about getting too much vitamin A, especially in supplement form. Vitamin A should especially be cautioned around pregnancy as excessive amounts of vitamin A are linked to birth defects and malformations. [7,8] In those with Gilberts syndrome, a genetic condition that increases bilirubin levels in the blood, vitamin A may slow the UGT enzyme further reducing the clearance of bilirubin. Even kids may be getting too much vitamin A, especially those who take supplements. 
Theory - Vitamin A : A toxin not a Vitamin?
There is a very interesting theory circling the internet that vitamin A and it's precursor, carotenoids, may not be a vitamin after all, but instead a toxin that is harmless at low levels but has a tipping point when it's storage in the liver is exhausted.The theory originates from Grant Genereux, who contends that vitamin A toxicity happens at far, far lower levels than documented in the literature and is a cause of body-wide poisoning and perhaps the real cause of autoimmune disease. You see, 90% of vitamin A is stored in your liver, and released into the bloodstream on a as-needed basis. But what happens when your liver's storage capacity is full? The theory assumes that when the liver is already overwhelmed by vitamin A, it accumulates in tissues and fat storage leading to systematic inflammation, most specifically noted in changes to the skin, bones, and vision.
According to Genereux, "If your average daily intake is more than your body’s daily usage, then it’s more or less inevitable. If you indulge just a little bit too much on milk, dairy, eggs, certain fish, etc. or any of the vitamin A precursors, then this will happen much sooner. If you supplement with cod liver oil, or a vitamin A supplement, or any vitamin A derivative; it will be much sooner. It could be in your twenties or teens or even at birth! It also depends very significantly on what fats you consume that vitamin A with."
Genereux also comments that "It simply boils down to the fact that we are all being very slowly potentially poisoned. If you’ve been living in North America for fifteen or more years, this definitely includes you. "
The verdict is still out on this theory, and the prevalence of vitamin A toxicity and subtoxicity is widely unknown. However, it's never a bad idea to check in on your own intake.
How to reverse vitamin A toxicity
If you suspect you've taken too much vitamin A through synthetic supplementation, there are a few things you can do right away.
First, take a look at all your multivitamins, supplements, lotions, prescription drug history, and beauty products to assess your intake. If there is excess, especially in supplemental form, consider eliminating it. Then take stock of your diet. If necessary, consider decreasing your intake of high vitamin A food for a period of time, like liver and loads of dairy, to give your body a vitamin A detox of sorts.
A vitamin A detox diet might be temporarily helpful to bring storage levels of vitamin A down (read more about the diet specifics here). In the simplest form, such a diet would consist of animal proteins, along with organic grains, as well as white fruits and vegetables (think white rice, white potatoes, cauliflower, parsnips, peeled apples, bananas, pears, raisins, dried cranberries, pineapple, etc).
Depending on the severity of the toxicity more drastic dietary measures or interventions might be necessary, so always talk to your doctor. As far as I'm aware, there is no quick, easy and accurate testing for vitamin A toxicity. Experimenting with your diet perhaps the most convenient and most insightful.
Bottom line: Get vitamin A from food sources and skip supplemental sources. If you're on a special diet that excludes retinol-rich animal foods, make sure you know your vitamin A genetics to prevent a deficiency situation.
Do you have a history of vitamin A toxicity? Please share in the comments!
Also published on Medium.