# Vitamin D

Category: Vitamins & Minerals

Also known as: cholecalciferol, vitamin D3, calcitriol

Vitamin D, specifically cholecalciferol (D3), is a secosteroid hormone-precursor whose primary evolutionary role is the regulation of calcium metabolism, a function so fundamental that it touches every cellular reaction in the body. Peat argued that vitamin D is the most…

12 passages · 3 authors · 2017–2021 · Most-cited: [Ray Peat](https://bioenergeticoracle.com/md/voices/ray-peat/index.md)

Canonical page: https://bioenergeticoracle.com/concepts/vitamin-d

## Synthesis

**Vitamin D**, specifically **cholecalciferol (D3)**, is a secosteroid hormone-precursor whose primary evolutionary role is the regulation of **calcium metabolism**, a function so fundamental that it touches every cellular reaction in the body. [Source 2] Peat argued that vitamin D is the most important immune-supporting nutrient for Americans, and its activity is as broad and complex as life itself. [Source 1, 2] The healthy human body produces cholecalciferol from cholesterol in the skin upon sunlight exposure; dietary sources from animals that have been in the sun, such as fish or dairy from pasture-raised cows, provide the identical molecule. [Source 5] Once in the bloodstream, the liver hydroxylates cholecalciferol into 25-hydroxy vitamin D, the beneficial storage form measured in blood tests, which supports protective, immune-enhancing effects. [Source 5]

The metabolic pathway of vitamin D involves a critical distinction between its precursor forms and its terminal, activated hormone. Cholecalciferol is converted in the liver to 25-hydroxy vitamin D, and subsequently in the kidneys to **calcitriol (1,25-dihydroxy vitamin D)**. [Source 4] Peat explicitly warned that calcitriol is the *toxic, dangerous last stage* of vitamin D handling, which intensifies calcification of blood vessels and kidneys and impedes healing. [Source 10] The production of calcitriol is driven by **parathyroid hormone (PTH)**, which rises in response to a deficiency of calcium or vitamin D. [Source 8, 10] Therefore, a high calcitriol level is not a sign of vitamin D sufficiency but rather a marker of a *deficiency state* and physiological stress, paralleling the degenerative actions of PTH itself. [Source 10] Supplementing cholecalciferol suppresses PTH, thereby *lowering* the dangerous active form, calcitriol. [Source 6, 8]

Dinkov has extended this framework by outlining a clinical criterion for supplementation based on the negative feedback loop between calcitriol and PTH. If calcitriol is elevated but PTH is not suppressed into the bottom 25% of the normal range, it indicates a resistance to the hormone's action, and supplementing D3 is considered appropriate to re-establish the feedback mechanism. [Source 3] Conversely, if calcitriol is high and PTH is already fully suppressed, further supplementation is unlikely to be beneficial. [Source 3] Roddy has summarized the broad anti-stress profile of cholecalciferol, noting it is **pro-thyroid**, **anti-cortisol**, **anti-prolactin**, and **anti-endotoxin**, effectively framing it as a pro-mitochondrial energy substance that aligns with the protective actions of progesterone and thyroid hormone. [Source 4, 11] Peat also noted that a vitamin D and calcium deficiency, or a phosphate excess, increases both serotonin and calcitriol, linking the stress pathway directly to bone loss. [Source 9]

The therapeutic use of vitamin D3 is distinct from the dangers of its metabolites. Peat stated that the beneficial forms are cholecalciferol and its liver-modified 25-hydroxy version, which act as neurosteroids similarly to DHEA or pregnenolone, while topical or internal use of calcitriol is damaging. [Source 10] Dinkov's formulation of a topical D3 supplement highlights its synergism with vitamin K in synthesizing **osteocalcin**, a hormone that reverses muscle aging and insulin resistance, and its interaction with the anti-aging gene *Klotho*. [Source 12] Peat dismissed the idea that vitamin D3 could cause hypothermia, and he rejected the argument that one should avoid supplementation because it merely increases a "storage form," calling such a view "terribly confused." [Source 7, 9] The consensus from this perspective is that vitamin D2 is metabolized differently and lacks the full protective effects of D3, and that adequate calcium intake is foundational to the entire system, as demonstrated by cave fish that thrive without vitamin D in mineral-rich water. [Source 1, 2]

## People also ask

### How does vitamin D3 supplementation lower the toxic form of vitamin D?

Peat explained that supplementing cholecalciferol suppresses parathyroid hormone, which is the primary driver of calcitriol production, thereby reducing the dangerous active hormone that promotes calcification.

### What blood markers indicate a genuine need for vitamin D3?

Dinkov described that elevated calcitriol alongside a parathyroid hormone level not suppressed into the bottom quarter of the normal range signals resistance, making D3 supplementation appropriate to restore feedback.

### Why is vitamin D3 considered a pro-metabolic hormone rather than just a bone nutrient?

Roddy summarized that cholecalciferol acts as a pro-thyroid, anti-cortisol, anti-prolactin, and anti-endotoxin substance, functioning as a neurosteroid that supports mitochondrial energy production.

## Related concepts

- [Aging](https://bioenergeticoracle.com/md/concepts/aging/index.md)
- [Bioenergetics](https://bioenergeticoracle.com/md/concepts/bioenergetics/index.md)
- [Bohr effect](https://bioenergeticoracle.com/md/concepts/bohr-effect/index.md)
- [Calcium](https://bioenergeticoracle.com/md/concepts/calcium/index.md)
- [Coconut oil](https://bioenergeticoracle.com/md/concepts/coconut-oil/index.md)
- [Glycine](https://bioenergeticoracle.com/md/concepts/glycine/index.md)

## Cited passages

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

### Source 1 — Ask the Herb Doctor: September 2021 KMUD

Ray Peat · Interview · Sep 17, 2021

> ## Vitamin D vs. D3
>
> **Caller:** What is the difference between vitamin D and D3? Which one should we take?
>
> **Ray Peat:** D3 is the normal one that we make when we are in the sunlight. It works the same chemically as the one we make. Some products on the market are vitamin D2; that is metabolized slightly differently and doesn't have all the good protective effects of vitamin D3. In a medical context, you might hear people talk about calcitriol. You don't want the triol—some people confuse that with vitamin D3. You want cholecalciferol (D3).

### 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

> **Kitty Blomfield:** awesome all right well let's just get let's get stuck into it you've got the question or should i ask the first question
>
> **Kate Deering:** yeah go ahead for that first okay
>
> **Kitty Blomfield:** all right i'll i'll cut the ribbon um dr pete can you please explain how vitamin d3 is utilized in the body what is its purpose um is it a vitamin or a hormone
>
> **Ray Peat:** Those are questions that the best researchers are just now starting to ask. For 100 years, people were treating it as just a calcium regulator, just a bone builder, a tooth builder, and so on. And their idea of calcium regulation was very limited. When you realize that calcium is involved in every possible cell reaction. It's everywhere in everything living. And it's a crucial regulator. And if vitamin D is mainly a calcium regulator, then that says the field of vitamin D activity is as broad and complex as a whole life question. So what's happening now in vitamin D research is just a few dozen people mostly starting to realize what the real issues are. And so that the field is very open and expanding with really interesting stuff happening. For example, when you look at it evolutionarily, it happens that fish don't really depend very much on vitamin D. Some experiments starving fish totally for vitamin D. Some of them developed spinal defects, but some didn't. Living in the ocean, minerals are very rich and it happens that even though fish are generally extremely high in vitamin D content, they don't pay much attention to it. It's very hard to create a vitamin D deficient fish. And much of the fish metabolism of vitamin D is getting rid of it. They accumulate it primarily from the food they eat, the plankton, mostly the animal zooplankton. And so it's just mostly a waste product for the fish. And if you think of the cave fish, the blind cave fish, there's no way they get sunlight or even plankton that has been in the sun. And still they manage somehow to have bones and to be alive and so on. Apparently caves generally being the result of water carbonic acid in water, dissolving away limestone. Cave water is generally very rich in minerals, especially calcium. So they are an example of a vitamin D free vertebrate that gets along with just calcium instead of vitamin D.

### Source 3 — #39 - The Great Vitamin D Debate with Georgi Dinkov, Danny Roddy, Kate Deering & Matt Blackburn

Georgi Dinkov · Interview · Mar 7, 2021

> **Georgi Dinkov:** Yes, active. Yes, so supplementary vitamin D is usually D3, known as cholecalciferol, or D2 calcifidio, which is what doctors prescribe usually at the dosage of like 50,000 units once weekly. For some reason, they don't prescribe D3. They like the D2. But both have the same metabolic pathways. And basically, ultimately, they go through the passage of 25-hydroxy-D3, which is the storage version. And then eventually gets activated in the kidneys to calcitriol, which is 125-dihydroxy-D3. So, if you talk to an endocrinologist, they actually, they themselves have this, one of the criteria for whether they should be looking at a vitamin D deficiency as something to be remediated or not touched at all is whether the negative feedback mechanism that's supposed to exist between the end product and the parathyroid hormone is there. And if your calcitriol is high and your parathyroid hormone is not at the very least in the bottom 25% of the normal range, This to the most endocrinologist means that at the very least supplementing vitamin D3 is not going to be a problem because you need to bring that PTH down to reestablish. the negative feedback mechanism. And if you have a, let's call it resistance, because that's what doctors like to use the term. If you have a resistance to that, to those receptors that the calcitriol is supposed to activate to trigger the negative feedback mechanism, endocrinologists think that in such a case, it's okay to supplement more. And sometimes they'll even prescribe even more calcitriol as an injection just to bring your PTH down. It's not very common, but it's an established protocol.

### Source 4 — Ep. 99 Interview Danny Roddy: The Wisdom of Ray Peat, and How Elevation Will Help You Live Longer

Danny Roddy · Interview · Nov 24, 2021 · https://www.youtube.com/watch?v=W7F-rIgoHd8

> **Lucas:** I think we got a good title for the show. Danny Roddy, Ray's Stupid Apprentice He Never Wanted.
>
> **Danny Roddy:** That would be the optimal title, I think, on the show.
>
> **Lucas:** Okay. Well, I haven't heard of this vitamin D debate. What is the debate over? I don't get it.
>
> **Danny Roddy:** Oh, yeah. It's difficult to say. You take cholecalciferol or vitamin D3, it's hydroxylized in the liver to, oh shoot, what's the other, calcifedol?
>
> **Lucas:** The activated form or whatever.
>
> **Danny Roddy:** Yeah, and then it activates again going to the kidneys and calcitriol or calcitriol or something. So that's like the 25D is the one made in the liver and then the 125 is the one made in the kidneys. And I won't really talk about it too much more because I just wrote a huge article on it. And I turned people to that article to see if they were interested in this debate or whatever. But it's kind of silly in my point of view. And I only wrote the article. It's on dannyrotty.substack.com. And the only reason I wrote that is the people promoting the idea that it's bad have large audiences. And so you know that quote, a lie can circle the world while the truth is still putting on our boots? That's kind of what's happened. It's... It's gone rampant, and there are very few people to defend vitamin D. To be honest with you, I think it's a life-changing thing. Thyroid, vitamin D, antibiotics, those are some things that... I don't think of myself as some amazing specimen or whatever, but those had a powerful impact on different aspects of my health, especially vitamin D. I want to stick up for it because I think it's a useful therapy. I think taking it off the table and saying that it's toxic is a tragic thing. I would act the same way if somebody said thyroid was toxic or progesterone was toxic. I would just laugh and think that it was... a laughable argument

### Source 5 — 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:** So just for the listener, can you basically let them know, I mean, the supplemental D is essentially cholecalciferol, correct?
>
> **Ray Peat:** Yeah, it's pre-vitamin D, the same stuff that fish eat and that we get out of fish. And if you think of people who were in the sunlight constantly producing their own conversion of cholesterol to cholecalciferol, they didn't need any from the environment. But when you move to the north, the only way to survive more than a season or so is to start eating some organism that still is in the sun and still producing cholecalciferol. So you either have to live on the coast and eat fish or eat animals which have been in the sunlight. So when you're near the equator and have around the year sunlight exposure, then you can be a vegetarian theoretically without the risk of a vitamin D deficiency.
>
> **Kate Deering:** So to kind of conclude that, I mean, what about consuming other foods that are high in vitamin D like dairy? Would that be also supportive?
>
> **Ray Peat:** Yeah. The cows were in the sunlight, and so they produced the same material exactly that fish produce by being in the sunlight or by eating algae that was in the sunlight or zooplankton that was in the sunlight.

### Source 6 — #39: Low Testosterone and PUFA | Vitamin D is Anabolic and Anti-Cortisol | High Metabolism and Aging

Georgi Dinkov (with Georgi Dinkov) · Interview · Nov 15, 2020 · https://open.spotify.com/episode/1ydUK0ut0jy7L37VbyLUmX

> **Danny Roddy:** Yeah, I think the enzyme is 1-alpha-hydroxylase. It's the PTH activates that to make... And the one other thing I'll throw out there... This isn't an argument to like, or it's not a view that you couldn't induce any harm taking cholecalciferol. Like we've talked many times on this podcast that it's possible for a supplement to be an allergen. And so if somebody takes it and they notice some wild effect or messes with their digestion or their mood or whatever, that's completely plausible to me. And a person should try it on their skin or a different brand or something else. But again, this idea, I don't know how familiar you are. You are familiar with this idea, right? That vitamin D is very toxic. It's kind of going around like wildfire. Oh, yeah.
>
> **Georgi Dinkov:** It says like, I mean... First of all, there were several threads on the forum, but I think there's several high-profile doctors, including Dr. Oz. I think they also – I think Mercola. They basically said like let's – we need to be careful about vitamin D because like we don't know enough about its like safety profile. And actually they pointed out – that calcitriol is known to be elevated in autoimmune conditions and bacterial infections and potentially even in conditions such as HIV. And they use that as an argument to not supplement with vitamin D3 because it's going to raise the levels of calcitriol. No, it actually lowers them.

### Source 7 — Dr. Ray Peat | Planned Obsolescence, Particulate Matter, The "Green" Reset, Soil, Wilhelm Reich, Social Structure, Digital vs Analog Reality, Morality and much more.

Ray Peat · Interview · Oct 29, 2020 · https://open.spotify.com/episode/6WSCCkil5E6bV0UXxIMsmy

> **Ray Peat:** What's being said is that you only need the active form, or not only, but that's what you'd be trying to increase, and by taking vitamin D supplements, you are increasing your storage form, and that that doesn't say anything. Who is saying that? I've been hearing that. Someone is terribly confused.

### Source 8 — #34 - How to live a pro-metabolic life with Danny Roddy

Danny Roddy · Interview · Feb 3, 2021

> **Kitty Blomfield:** And
>
> **Danny Roddy:** I hope I'm steelmanning their argument right now. If I'm getting this wrong, please email me or message me. But as I understand it, they're talking about focusing on active vitamin D, which is called calcitriol. And... That sounds like something really important, right? Active vitamin D. That sounds like the best form of vitamin D. And they're saying too that taking cholecalciferol, which is vitamin D3, the kind that people normally supplement, is the storage form, which is stored in your liver. And they're saying that that's harmful and excess or causes calcification and other problems apparently. Which is odd because if anybody's familiar with, right, Pete, you talked about parathyroid hormone and things like prolactin, which are prolactin is a pituitary hormone. Parathyroid hormone is released from four glands in close proximity in the back of your thyroid. Right. And so those tend to break down the bone and release calcium into the blood. And the high parathyroid hormone in prolactin and the breaking down the bone and releasing calcium into the blood is actually the thing that drives the soft tissue calcification where you don't want calcium. And then that can turn on nitric oxide and all these bad things. So this is why Ray is so kind of... focused on calcium. He's always talking about getting like 2000 milligrams of calcium and getting your vitamin D. It's to lower the parathyroid hormone, the prolactin and all the associated hormones like serotonin, aldosterone. And so with their argument saying that don't focus on the cholecalciferol, the vitamin D3, focus on the active 125 hydroxy, it's actually a little bizarre because parathyroid hormone, again, the thing that you do not want... elevated turns on an enzyme called, I think it's called one alpha hydroxylase that makes the one 25 hydroxy active vitamin D.

### Source 9 — Ray Peat Email Advice Depository — Post 536

Ray Peat · Email · Feb 27, 2019

> ## Thread 6
>
> **Question:** I apply D3 on my shoulders and chest. Sometimes, I feel cold when I apply it. I read online that vitamin D can sometimes cause hypothermia. What is your opinion about that?
>
> **Ray Peat:** I don’t think it can cause hypothermia. Have you checked your temperature?
>
> **Question:** I always have the AC on and the cold air hits my feet. I take vitamin D dissolved in SFA esters and ethanol and my feet start to feel cold all of the sudden, so I have to turn the AC off. When I take vitamin D dissolved in MCT oil, I don’t feel that much cold. So I don’t know what’s going on here.
>
> **Question:** I recently read a study that claims vitamin D3 increases TPH2, which means vitamin D3 can increase brain serotonin. I read natural progesterone can reduce TPH2, but I don’t want to supplement with progesterone because it has some anti-androgenic effects on me. What are some tools I can take to reduce TPH2 when I supplement with vitamin D3?
>
> **Ray Peat:** I think it’s calcitriol that does that, and a vitamin D and calcium deficiency or phosphate excess increases calcitriol. Serotonin tends to cause bone loss, increasing parathyroid hormone.

### Source 10 — Dr. Ray Peat | Planned Obsolescence, Particulate Matter, The "Green" Reset, Soil, Wilhelm Reich, Social Structure, Digital vs Analog Reality, Morality and much more.

Ray Peat · Interview · Oct 29, 2020 · https://open.spotify.com/episode/6WSCCkil5E6bV0UXxIMsmy

> **Ray Peat:** Not the steroid form, it's the active form that acts as a neurosteroid, for example. It affects physiology, the function, as well as the expression of genes in the brain and other tissues, the way a steroid hormone, DHEA or pregnenolone, modifies the tissue. might not be active in the sense of having been converted by the kidney. But that process, calcitriol, that's the form that when they use it topically, for example, on the cornea, it impedes, damages the healing process. If you take it internally, it intensifies calcification of blood vessels. and the kidneys, it's the toxic, dangerous vitamin D. You don't want to take activated, active vitamin D. That is properly thought of as the dangerous last stage of vitamin D handling, which is increased in proportion to your vitamin D deficiency. not getting enough calcium and or vitamin D from sunlight or diet and a rich source of calcium in the diet relative to phosphate your parathyroid hormone increases and in the process it increases a lot of degenerative increase of calcium in your arteries and other soft tissues, and it increases the activation of vitamin D. So the active form, so-called, is chemically 1,25-dihydroxy cholecalciferol. The good kind is either cholecalciferol, which or the liver-modified 25-hydroxy cholecalciferol. That isn't the kind we take, but that's the kind that increases when we take cholecalciferol. It's activated in the liver and becomes the beneficial, protective, immune-supportive, sounds a lot like what parathyroid hormone would do. Exactly. It parallels the actions of parathyroid hormone and stress. It's increased under the influence of

### Source 11 — Telegram - Danny Roddy - 2021-07-28

Danny Roddy · Telegram Message · Jul 28, 2021 · https://t.me/dannyroddy

> # Telegram - Danny Roddy - 2021-07-28
>
> **Danny Roddy** - 11:19
> Milk, tangerines, and oranges.
>
> **Danny Roddy** - 12:45
> Vitamin D (cholecalciferol) has been found to be:
>
> • Pro-thyroid
> • Pro-progesterone
> • Anti-aldosterone
> • Anti-cortisol
> • Anti-parathyroid hormone
> • Anti-prolactin
> • Anti-endotoxin
> • Anti-adrenaline
>
> In other words, it's pro-mitochondrial energy and anti-stress.

### Source 12 — Calcirol — IdeaLabs Cosmetic Ingredient

Georgi Dinkov · Product · Dec 10, 2017 · https://idealabs.ecwid.com/Calcirol-p97685585

> One of its most mysterious roles identified so far is the interaction with (and possible activation of) the anti-aging gene Klotho, which Peat mentioned quite a few times in his interviews.
>
> [references]
>
> Another hugely important role is the synergism of vitamin D with vitamin K in the synthesis of osteocalcin. Elevating the levels of osteocalcin has been shown to completely reverse the aging of muscle tissue, and possibly negate the age-associated loss of muscle mass. In addition, osteocalcin has been shown to reverse insulin resistance, restore proper steroid synthesis to youthful levels, and prevent the metabolic changes that occur in cells with aging and can lead to virtually all chronic conditions including cancer, diabetes, CVD, dementia, autoimmune conditions (MS, Lupus, RA) etc.
>
> [references]
>
> Last but not least, blood levels of vitamin D are a good surrogate for thyroid function even in the presence of euthyroid biomarkers. Given the widespread prevalence of vitamin D deficiency or insufficiency in the population of most Western countries, I think everybody gets the idea of just how "healthy" people in developed countries currently are. In regards to those widespread deficiencies - a recent study found that the current official guidelines (RDA) for vitamin D supplementation are wrong due to a statistical mistake. As such, almost 9,000 IU (vs. the RDA of 400 IU) daily are needed as a supplement by adults to achieve the optimal blood vitamin D levels. The study also claims the warnings of side effects are unfounded due to the incorrect RDA and calls for medically unsupervised supplementation of 10,000 IU daily for adults and 3,000 IU daily for children older than one (1).
>
> [references]
>
> The name Calcirol is an old and seemingly forgotten synonym for cholecalciferol (vitamin D3), and it conveys well IMO the main properties of this chemical - i.e its role in calcium metabolism.
>
> The units listed on the label are just for measurement purposes. They do not indicate or suggest optimal dose.
>
> ---
>
> Calcirol contains the secosteroid cholecalciferol, also known as vitamin D3. Aside from its well-known role in calcium metabolism, this secosteroid has very important role in immune function, muscle health, stress adaptation (cortisol), anti-aging, sex steroid modulation, cardiovascular function, cognitive function, etc.

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