# Vitamin A (retinol)

Category: Vitamins & Minerals

Also known as: vitamin A, retinol, retinyl palmitate

Vitamin A (retinol) is a fat-soluble vitamin whose biological activity is so tightly coupled with thyroid hormone that they share a single transport protein, transthyretin, and are taken up by cells together. Peat argued that vitamin A is essential for the production of all…

11 passages · 3 authors · 2009–2022 · Most-cited: [Ray Peat](https://bioenergeticoracle.com/md/voices/ray-peat/index.md)

Canonical page: https://bioenergeticoracle.com/concepts/vitamin-a-retinol

## Synthesis

**Vitamin A (retinol)** is a fat-soluble vitamin whose biological activity is so tightly coupled with thyroid hormone that they share a single transport protein, **transthyretin**, and are taken up by cells together. [Source 3, 4, 9] Peat argued that vitamin A is essential for the production of all steroid hormones from cholesterol, for protein synthesis in skin and hair, and for the maintenance of mucous membranes. [Source 4] He noted that a high metabolic rate dramatically increases the requirement for vitamin A because it is consumed in the production of large amounts of **pregnenolone** and **progesterone**. [Source 7] This functional partnership means that in hypothyroidism, the precursor *carotene* cannot be converted to active retinol, leading to its accumulation in steroid-forming tissues and a visible yellowing of the calluses on the palms and soles. [Source 3]

The relationship between vitamin A and thyroid function is bidirectional and can be antagonistic in extreme situations. Peat explained that because thyroid hormone and retinol travel on the same protein, taking a massive supplement like 100,000 units can displace thyroid hormone, causing a noticeable dip in thyroid activity in borderline individuals. [Source 2] Dinkov elaborated on this, citing a human dose-escalation study in obese, hypothyroid women which found that up to **25,000 units daily** produced no side effects even in severely compromised subjects, establishing a practical upper threshold for sensitive individuals. [Source 8] He further noted that the toxicity symptoms in animal and human studies do not typically manifest until doses reach the hundreds of thousands of units taken for at least six months. [Source 6] To mitigate the risk of vitamin A inhibiting thyroid function or undergoing *autoxidation* into toxic metabolites, both Peat and Dinkov recommend combining it with **vitamin E**. [Source 1, 8]

Peat directly challenged the conventional narrative of vitamin A toxicity, suggesting that the famous polar bear liver poisoning was likely caused by *algae toxins* stored in the liver rather than the vitamin itself. [Source 4] He suspected that many toxicity reports were fabricated to promote synthetic retinoids. [Source 4] Dinkov reinforced this distinction, emphasizing that the severe birth defects and liver toxicity associated with "vitamin A" are attributable to synthetic analogs like **Accutane** (isotretinoin), which have extremely long half-lives and are treated as toxins by the body. [Source 6, 10] In contrast, the natural esters *retinyl palmitate* and *retinyl acetate*—which are the body's own preferred storage forms in the liver—have been used in trials at doses up to 500,000 units daily without long-term toxicity. [Source 8, 10, 11]

A deficiency or an excess of vitamin A can produce similar symptoms due to a self-catalyzing breakdown process. Peat described a state where an overdose, in the context of a deficiency in other antioxidants, causes retinol to catalyze its own destruction, leading to tissue breakdown such as chapped lips from defective protein synthesis. [Source 1] He recommended interrupting this cycle with vitamin E or progesterone rather than continuing supplementation. [Source 1] Dinkov added that vitamin A is a crucial cofactor for steroidogenesis, and a deficiency can manifest as poor night vision, acne, dandruff, and an inability to produce protective hormones. [Source 9, 11] He noted that vitamin A supplementation often makes vitamin D supplementation smoother and less likely to cause irritability or insomnia, suggesting a synergistic requirement among the fat-soluble vitamins. [Source 5, 6]

## People also ask

### How does vitamin A interact with thyroid hormone?

Peat argued that vitamin A and thyroid hormone share the transport protein transthyretin and are taken up by cells together, meaning a high metabolic rate increases vitamin A demand while large supplemental doses can displace thyroid hormone and lower thyroid activity in borderline individuals.

### What distinguishes natural vitamin A from synthetic retinoids in terms of safety?

The corpus describes how Dinkov emphasized that severe toxicity and birth defects are linked to synthetic analogs like Accutane, whereas natural esters such as retinyl palmitate have been used in trials at doses up to 500,000 units daily without long-term toxicity.

### Why can both a deficiency and an excess of vitamin A cause similar symptoms?

Peat described a state where an overdose, in the context of low antioxidants, causes retinol to catalyze its own destruction, leading to tissue breakdown like chapped lips, while a deficiency impairs protein synthesis and steroid hormone production, producing overlapping signs of tissue deterioration.

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## Cited passages

Passage numbers match the `[Source N]` markers in the synthesis above.

### Source 1 — One Radio Network: Nothing is as it seems with COVID (July 20, 2020)

Ray Peat · Interview · Jul 20, 2020

> **Ray Peat:** Either a deficiency or a great excess of vitamin A acts the same. If you're deficient in all of the antioxidant things, all of the stabilizing factors of which vitamin E is just one, if you're deficient in those, an overdose of vitamin A leads to autoxidation. The vitamin A starts catalyzing its own breakdown. And the supplements of retinoic acid, There are three forms of it. Two of them are extremely toxic. The third one, it's a matter of having it in great excess. All of those forms of retinoic acid normally are locally derived in very particular tissues. For example, the developing embryo is the most noticeable place where you use retinoic acid to create tissues such as the eye. But if it's out of place, then it has a toxic effect and leads to the breakdown of the basic safe form, retinol, which is the form that occurs mostly in foods. the retinol begins to be destroyed when you've started catalyzing the breakdown. So it's very hard to know whether to use any supplement at all. I would suggest if you have those symptoms to rely only on foods such as milk and eggs for your vitamin A rather than a supplement.

### Source 2 — Vitamin D, Calcium and Mineral Metabolism with Dr. Ray Peat and Kate Deering

Ray Peat · Interview · Aug 11, 2021 · https://www.youtube.com/watch?v=ur9F7THGBLg

> **Kate Deering:** Okay, so what you're saying is even though vitamin A is needed in the vitamin D metabolism, it really wouldn't matter if you started supplementing even somewhat high dose of D. It wouldn't throw off your other nutrients if the other ones weren't being supported at the same time unless you were extremely deficient in them.
>
> **Ray Peat:** Yeah. Yeah. And vitamin A and thyroid. have a noticeable interaction so that if you're borderline for thyroid function and take a huge vitamin A supplement such as 100,000 units, you will probably experience a dip in your thyroid activity because thyroid hormone and retinol travel on the same protein and so you'll simply displace one by too much of the other but that is noticeable only in extreme situations
>
> **Kate Deering:** I see. I had a thought, and then it left my brain. So we'll go to the next question, which is, should people ever take a calcium supplement? Or are they harmful?
>
> **Ray Peat:** No, they should get it from food. But for example, eggshells or powdered oyster shells. You can think of it as food instead of throwing away the shell of the egg. why not powder it up and add it to your omelet? It's in a form that is very assimilable by most people. So calcium carbonate, I don't think is a problem to use as a calcium supplement. But some of the counter ions, have their own activity, so you don't want to take very big doses of calcium lactate or calcium gluconate, for example, just because that counter ion can have its own metabolic action.

### Source 3 — Herb Doctors: Thyroid, Polyunsaturated Fats And Oilsnew

Ray Peat · Interview · Apr 1, 2009 · http://l-i-g-h-t.com/files/herb-doctors-thyroid-polyunsaturated-fats-and-oils-new-56-mins.mp4

> **Ray Peat:** And vitamin A and thyroid work so closely together biologically that the protein that transports them is a single protein. It’s called transthyretin for retinol and thyroid transport. And in the 1930s, one of the ways of confirming that a person had died from hypothyroidism was that the steroid-forming tissues turned red because of the accumulated keratin because you can’t use vitamin A if you don’t have thyroid. And so, the keratin accumulates in the steroid-forming tissue. It makes them red.
>
> **Andrew Murray:** Would this be any reason behind the basis of people with yellow calluses being very apparent on their soles or their palms?
>
> **Ray Peat:** Yeah. That’s one of the old ways to diagnose hypothyroidism.
>
> **Andrew Murray:** Okay.
>
> **Sarah Johannesen Murray:** No, I think you’ve told this out before, Dr. Peat. We are going pause here for a moment.
>
> **Andrew Murray:** Okay. You are listening to Ask your Herb Doctor on KMUD Garberville 91.1 FM. And from 7:30 until the end of the show at 8 o’clock, you are invited to call in with any questions related or unrelated to this month's topic of thyroid disorder. And we can hopefully cover iron and a few other subjects. But, again, this month we are very pleased and fortunate to welcome Dr. Raymond Peat back to the show and we are going to be continuing to examine some common misconceptions surrounding the thyroid treatment. Okay. So did you want to carry on with…?

### Source 4 — Ask the Herb Doctor: Postpartum Depression

Ray Peat · Interview · Jun 21, 2019

> ## Vitamin A Toxicity Myths
>
> **Andrew Murray:** A listener asked about a website claiming chronic Vitamin A toxicity is the cause of autoimmune diseases. What is your view?
>
> **Ray Peat:** Vitamin A is used to make all steroid hormones from cholesterol. Thyroid and Vitamin A travel together on a protein in the blood and are taken up by cells together. You don't produce steroid hormones without Vitamin A. It is used in protein synthesis; hair and skin will fail if you are deficient. Mucous membranes stop producing mucus without it. I looked through the book claiming toxicity and couldn't find any facts.
>
> **Andrew Murray:** What about the famous polar bear liver toxicity?
>
> **Ray Peat:** That has been cited in textbooks for 80 years as proof Vitamin A is toxic. But polar bears sometimes eat fish poisoned by algae, and their livers store that toxin. The explorers likely got algae toxin via the bear liver. When drug companies were releasing Retin-A, there were sudden news releases about Vitamin A causing blindness. I tried to verify one report at the University of Oregon and couldn't get any confirmation. I think they were made up to create a desire for synthetic Vitamin A.

### Source 5 — IdeaLabs Forum Q&A — Retinil

Georgi Dinkov · Forum Q&A · May 8, 2015

> **mirc12354:** (2016-07-21) Is there a mistake in first statement or I just I don't get this?
>
> **Georgi Dinkov:** (2016-07-21) Yes, the first statement is incorrect. What I meant to say that 1 IU of retinyl acetate is equivalent to 0.87 IU retinol, and 1 IU retinyl palmitate is equivalent to 0.5 IU retinol. So, retinyl acetate has higher retinol equivalency compared to retinyl palmitate per IU of each chemical.
>
> **Amazoniac:** (2016-07-21) Review: I don't have any miraculous experience to share. I just want to comment that the product is excellent. It is just what I was looking for to have at hand: a simple, high-quality and pure vitamin A. The smell is pleasant and I noticed that when I'm (probably) lower on vitamin A, it appears more pleasurable; the opposite also occurs.
>
> **Georgi Dinkov:** (2016-07-21) Thank you! I am not expecting or selling miracles, this review is great - i.e. realistic and reasonable.
>
> **Amazoniac:** (2016-07-21) Yeah, but it must be nice as a seller to read one of those stories..
>
> **Georgi Dinkov:** (2016-07-21) Yep, it makes my day actually. Thanks!
>
> **EIRE24:** (2016-09-23) @haidut Is it safe to take the vitamin A in isolation of the other fat soluble vitamins? Would it be better to dose the A high and then take the other fat solubles to balance it all out?

### Source 6 — Nitric Oxide and Methylene Blue [Generative Energy #11]

Danny Roddy · Interview · Nov 1, 2015 · https://www.youtube.com/watch?v=GgeZJoir70w

> **Georgi Dinkov:** I do agree. Unfortunately, modern medicine has done a very good job of scaring people away from taking the natural vitamin A that is available. I shouldn't call it natural, but basically you can buy the actual retinol, which is the natural form that exists in the body. which then gets converted to the active retinoic acid. Or you can buy one of its esters, retinyl palmitate or retinyl acetate. Basically, I think the official RDA recommendation is no more than 5,000 units of either retinol or the retinol equivalents like the palmitate and the acetate. And that is a puny dose. If you actually have properly functional thyroid, I think the estimate... And I've confirmed this by looking at all of the animal models that have worked with supplemental vitamin A so far. And when you convert the dose to a human dose, when they feed the animals the so-called normal diet, the one that contains normal levels of vitamin, in other words, to prevent deficiency, the human equivalent dose is always upwards of 20,000. international units per day and the the toxicity symptoms in animals and it's been tested in humans as well they don't start to manifest until you reach the hundreds of thousands of units taken for at least six months there was a recent clinical trial with humans with natural vitamin a for acne and they basically concluded two things number one In order for the natural vitamin A's to be effective, females needed between 200,000 and 300,000 units per day for at least three months, males between 400,000 and 500,000 international units per day for six months. And none of them had any signs of toxicity. I think they tested liver enzymes. some people had was slight nausea. So the study concluded by saying, unfortunately, this safe and effective vitamin has been demonized unnecessarily. So there you have it. But then on the other hand, doctors have no problem recommending tretinoin, which is known to turn fetuses into abominations.

### Source 7 — World Puja: Foundational Hormones

Ray Peat · Interview · Nov 23, 2012 · http://l-i-g-h-t.com/files/world-puja-foundational-hormones.mp4

> ## Cholesterol and Pregnenolone
>
> **Taya Skerry:** Unless people eat chicken livers or egg yolks, they probably aren't getting enough retinol (Vitamin A).
>
> **Ray Peat:** Yes. If your metabolic rate is high, your Vitamin A requirement is very high because you will be producing large amounts of pregnenolone and progesterone, which uses up Vitamin A. Sometimes people notice that in bright sunny weather they get acne or dandruff. If they take a supplement of Vitamin A—while watching their thyroid, because Vitamin A can inhibit thyroid function—they are able to make the progesterone and pregnenolone needed to respond to the long summer days.

### Source 8 — #37: Harmful Meditation? | Intermittent Fasting is Dangerous | Obesity Paradox | Current Events with Georgi Dinkov

Georgi Dinkov · Interview · Oct 17, 2020 · https://open.spotify.com/episode/1NbBhbjAXOTRJj9KyYRA9N

> **Georgi Dinkov:** Most of the vitamin A in liver is palmitate. That's the preferred ester for storing vitamin A in mammals, or at least in... in mammals like humans and monkeys and most of the mammals that you're going to get the liver from, like cows, I don't know, cows, goats, sheep, et cetera. So yeah, if you're eating liver, you're eating mostly retinol, palmitate, and a little bit of free retinol. Maybe a little bit of retinoic acid as well, but a tiny amount compared to the amounts of retinol and especially retinyl palmitate. As far as getting almost all of your vitamin A from preformed vitamin esters like palmitate or acetate, I don't see a problem with it. I think it's basically at this point, if the foods that we're eating, the commercial ones, weren't fortified additionally with preformed vitamin A, we'll all be having vitamin A deficiency because it's actually very rare now. If you take the commercial foods, if they aren't fortified, we'll be getting – so what I'm trying to say is most of us these days are getting our vitamin A from preformed esters because they were added to the food. And there doesn't seem to be a rampant vitamin A deficiency going around. So apparently it works. So I don't see a problem. As far as the dosages, it's really tricky because for hypothyroid people, vitamin A can be – I don't want to say dangerous, but it can exacerbate the symptoms if you take too high dosage like in a single time. But the one human study that I know that looked at actually obese hypothyroid women and did a dose escalation test – They found out that up to 25,000 units daily produce no side effects, even in severely compromised, health-wise, hypothyroid, obese, diabetic women. So that would be the most that I would take.

### Source 9 — The Peat Whisperer

Danny Roddy · Book · 2012

> ### Key Ideas
>
> **Danny Roddy:** Vitamin A: Special consideration should be given to vitamin A in the form of retinol. Vitamin A is crucial for the production of all sex hormones and is so intertwined with thyroid function that thyroxine (T4) and vitamin A share the same protein (transthyretin). Signs of vitamin A deficiency can be poor night vision, calluses on the palms and bottoms of the feet, acne, and dandruff. Calcium Cofactors: Besides calcium’s role in supporting the metabolic rate and suppressing numerous stress hormones, calcium’s cofactors are essential for its absorption and utilization. Special consideration should be given to vitamin D, vitamin K, and sodium. Sodium: Similar to calcium, adequate sodium in the diet can support the metabolic rate, increase the production of carbon dioxide, and suppress a variety of stress hormones. Cholesterol: Dietary cholesterol (liver, eggs, milk) protects the structure of the cell, increases oxidative energy, and provides the raw material for synthesis of sex hormones. Copper: The crucial respiratory enzyme, cytochrome c oxidase, is dependent on copper, thyroid, and light. Similar to vitamin A, increasing the metabolic rate will require additional dietary copper. Selenium: The deiodinase enzymes that convert thyroxine (T4) to triiodothyronine (T3) depend on selenium and glucose for their conversion. [references]

### Source 10 — #110 - Why your skin is a reflection of your internal health with Emma Sgourakis & Georgi Dinkov

Georgi Dinkov · Interview · Apr 25, 2022

> **Kitty Blomfield:** So, Emma, what would you say, like, what are some dietary changes that people can make and focus on if they're trying to improve their skin?
>
> **Emma Sgourakis:** I think like Georgi was saying, you know, when you get yourself in such a state and, you know, thyroid is that low. beyond tracking down Georgi's stuff and looking into some, dabbling with some of his wonderful Tyra Mix and Tyra Max and things like that, I think getting it back to basics as you always, you know, educate your clients with Kitty, but perhaps making it easier on their digestion to start with, making sure there's sufficient protein, definitely. Perhaps with smaller, more frequent meals, put less load on the system. I think salt's really important too, and... It's something that still so many people are scared to really amp up their salt. But I would say, yeah, I mean, the vitamin A and all the precursors to generating... you know, healthy. But this is another thing too, isn't it? And that's one thing I wanted to, you know, quiz you on Georgi is that with the vitamin A thing, you talk about the synthetic, quite toxic forms of vitamin A that you use to treat skin conditions. And there's that association with that. And for women who are pregnant or wanting to get pregnant. that's sort of ingrained in them you know caution those because of birth defects but then they associate that vitamin a with healthy food source vitamin a and and a lot i get asked but but should i be eating liver if i'm considering getting pregnant or what if i'm pregnant now my obstetrician has recommended to cut back on dairy definitely don't touch liver anything with vitamin a they're terrified of because of birth defects where you know um Tell me if I'm wrong, but there was some great articles that Ray sent me years ago and looking at the only birth defects that really did, that really were associated with vitamin A were due to synthetic vitamin A's at super high doses.
>
> **Georgi Dinkov:** Yeah, a million units per day. And hopefully, I mean, those kind of those are used on people with leukemia, well-established treatment. And of course, back in the day when there weren't the synthetic vitamins, synthetic versions available, they were using plain old retinol, vitamin A, to treat leukemia. And of course, if you ask the doctors, they don't want you to mention that because it's going to destroy their sales. Anyways, back in the day when they were using up to a million units a day to treat leukemia, they noticed no toxic side effects, no liver failure, because that's nothing they care about. It's going to kill your liver, right? None of these side effects were seen with either plain retinol. You know, ideally preformed retinoic acid, but it's really expensive and hard to find, and usually only chemical companies sell it. Retinol is more available, but it's relatively unstable. So the most common supplements with vitamin A use one of the esters, like retinyl palmitate or retinyl acetate, and those still metabolize in the body to retinol. Still, even if you use up to a million units a day, which for acne is a tremendously high dose, most people who use vitamin A for acne use like maybe 50 to 100,000 units a day, and that's plenty. And at those dosages, there's never been shown to be a birth defect in a human or an animal. All of the birth defects, as you said, we're seeing in animals or humans using one of the synthetic varieties, and especially the infamous Accutane. And now they're thinking one of the reasons is because it has such a long half-life, and the molecule itself, it's really incompatible with many of the other enzymes in the body. So it treats it as a toxin, but it's hard to get rid of because it stays in the tissue for so long. So all these fear-mongering tactics apply strictly to the synthetic versions. And some people will say, well, retinol palmitate and acetate are also synthetic, which is true.

### Source 11 — #31: Estrogen for Libido? | PUFA and Hypogonadism | Overpopulation Hoax | Parabiosis | Cancer with Georgi Dinkov

Georgi Dinkov (with Georgi Dinkov) · Interview · Jul 19, 2020 · https://open.spotify.com/episode/6mO0fuDYLfG6rZQYQs1oT5

> **Danny Roddy:** Yeah, not to beat a dead horse, but but I think I'd be interested in your thoughts on this. But if you're like getting into thyroid and changing the nutrition and all these things, I think supplementing progesterone DHEA might be one of the most confusing things to try to incorporate. Like I I don't know if that's like again, nobody has to follow my train of thought with how to what to supplement or what to eat or whatever. But I just think that's a confusing place to. kind of begin with all this, like immediately supplementing progesterone and DHEA. Because again, increasing your own thyroid function, whether that be getting more sunlight or eating a good diet or increasing the calcium, that will allow a person to make their own progesterone and DHEA. That might just make things a lot easier than immediately supplementing, which can be challenging sometimes.
>
> **Georgi Dinkov:** Yeah. And vitamin A, which is a very needed cofactor, Some people got spooked by that thread on the forum of the vitamin A toxicity. But keep in mind that vitamin A, the regular retinol and the safer retinol acetate and palmitate, the safer esters, have been tried in humans in dosages up to 500,000 units daily without any toxic toxicity or long-term side effects. In fact... FDA, considering how conservative it is in its RDA, and came up with most of these estimates by preventing malnourished prisoners from dying, right? It's not exactly optimal for health. Even their own guidelines say that 25,000 units daily, which is a pretty hefty dose, is unlikely to hurt even the most sensitive people that may already have vitamin A toxicity in them.

_Generated 2026-07-20 from the Bioenergetic Oracle corpus._