> The evidence is clear that vitamin D toxicity is one of the rarest medical conditions and is typically due to intentional or inadvertent intake of extremely high doses of vitamin D (usually in the range of >50,000-100,000 IU/d for months to years).
It's really important to follow the sources when you see something like this quoted. The article you link to is not an actual study in which people were given Vitamin D. It is a review article, and the specific sentence you quote references an article by Michael Holick, who then references two other articles. One of those articles is just a review, not citing new evidence.
The one piece of evidence that these are all referring back to is a small study done in men in high latitudes in winter, when skin production of Vitamin D is decreased. It consisted of a small number of patients who were randomized to receive different amounts of Vitamin D, so only a small number actually got 10,000 units a day, the highest dose. And this was over a period of just 5 months. You can read the article here: https://pubmed.ncbi.nlm.nih.gov/12499343/
Note that the highest dose in this study was 10,000 units a day, which I would agree can be safe for some people over a short period of time. But it was not necessary in this study to attain goal Vitamin D levels, and over time that dose can definitely cause problems.
Also, where is the 50,000 to 100,000 unit evidence coming from? I'm not sure actually, since there are no human studies looking at that dose. This may be a "theoretical" dose based on studies in other animals, or a false extrapolation based on human studies.
Also, Michael Holick is a controversial figure. A lot of the articles pushing high doses of Vitamin D lead back to him. Please read this NY Times article for a great summary of his issues: https://www.nytimes.com/2018/08/18/business/vitamin-d-michae...
> The knowledge about toxicity from hypervitaminosis D in terms of dosage and duration is limited. Because of the high heterogeneity in reported amounts of vitamin D intoxication cases, it is not possible to calculate a reliable mean value that will invariably induce toxic effects. The highest daily dose hitherto reported in the literature is about 2,000,000 UI/day that has led to intoxication in a couple of months
> Moreover, the highest cumulative dose (657,000,000 UI) leading to toxicity was obtained after 36 months of treatment with cholecalciferol 600,000 UI/day
Figured people can Google, all I bring is awareness this is widely overblown, having taken myself, for therapeutic purposes, upwards of 100k IU per day for months without doctor supervision (but doing it correctly, with a very low calcium diet). People take vit D megadoses for autoimmunity, with significant success, but I'm not discussing this here.
Since you seem to be an expert: What about different forms of vit D? I vaguely remember discussions about pills not being absorbed well. Also I remember people talking that vit D intervention fails to do anything besides raising the blood levels, indicating that things might be more complex. I'm interested in the topic, but never really dived into it.
There are only two forms, the plant/mushroom form (D2) and animal (D3) form.
As with anything fat-soluble it's wise to take it as part of a meal that includes plenty of fat.
The problem with most studies is, surely in part because of this unfounded fear, they are underdosed. I don't have anything on hand, but I know there are clinics supervising megadose vitamin D protocols all over the world, but mostly in Germany and Latin America, that I'm aware of.
It really means complete elimination or drastic reduction in anything high in calcium, even water can have quite a bit. But this was, again, with extremely high doses. I don't currently follow the protocol, as I do other things, but I sometimes take high doses for a few days.
When I had my first major flare-up, I tested at 7ng/dl (near bottom half of the severe deficiency range). That's what lead me to pay attention to this subject.
>People take vit D megadoses for autoimmunity, with significant success,
You mean for compensating for the low vit D levels due to constant inflammation seen in autoimmunity? or to decrease autoimmunity? I have autoimmune diseases and my vit D goes down to about 7 ng/mL without supplementation, so I'm curious.
That's the same level I had when I got very ill, it's near the bottom half of the insufficiency range, you should definitely consider supplementing and monitoring it.
Per your question, the latter, the theory is autoimmunity is exacerbated in a certain genetic makeup, and to compensate for it by megadosing.
This is one case report. Yes, this person took an insane amount of Vitamin D and ended up very sick from it. But we can't really conclude that amounts under her dose are safe.
does not jive with the documented case of 2M IU (50mg) per day for months, nor with this case:
> Two patients, a Caucasian 90-year old man and a 95-year old woman, were monitored from 1 h up to 3 months after intake for clinical as well as biochemical signs of vitamin D intoxication. Blood vitamin D3 concentrations showed a prompt increase with the highest peak area already hours after the dose, followed by a rapid decrease to undetectable levels after day 14. Peak blood 25(OH)D3 concentrations were observed 8 days after intake (527 and 422 nmol/L, respectively (ref: 50–200 nmol/L)). Remarkably, plasma calcium levels increased only slightly up to 2.68 and 2.73 mmol/L, respectively (ref: 2.20–2.65 mmol/L) between 1 and 14 days after intake, whereas phosphate and creatinine levels remained within the reference range. No adverse clinical symptoms were noted.
