When that came out a few years ago [1], I began getting my vitamin D tested through my doctor and slowly ramped up my dosage. It went from 28 ng/mL (70nmol/L) [2] to 32-35 ng/mL (80-87.5 nmol.L). In my own physiology, this required 4,000 IU (100 mcg) daily, orally. 2,000 IU was not quite enough.

I'm going to add another 2,000 IU daily to see if I can reach the recommended 100 nmol/L from the OP. [3]

[1] https://news.ycombinator.com/item?id=15867918

[2] converter here: https://www.azcalculator.com/calc/vitamin-d-ngml-nmolL-conve...

[3] https://pubmed.ncbi.nlm.nih.gov/28768407/

Now, there is a difference between "ramping up" levels and maintenance levels, right?

It's generally been found that larger doses are required to move the blood levels up, but it doesn't seem like people need to remain at those dosages to maintain those levels.

A few things.

Whenever your conclusion is that the "official recommendations are flawed", and those were in place for a while now, scrutinize your process. Reading a post on social media is rarely paradigm-changing - and when it is, it's overwhelmingly in the wrong direction.

Secondly, the 8k dose doesn't seem realistic historically. Is there any diet that does not include the products of modern tech, that gets anywhere near those levels consistently? Doesn't seem likely.

Megadoses of anything are not without issues. There will be side-effects with vit D, esp. related to calcium, etc.

The data on the possible connection between vit D and respiratory illness is still way more sketchy than most people assume. There is no solid research yet.

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That being said:

Vit D deficiency is pervasive in a lot of places. Most people would benefit from taking some supplementation.

1000 UI capsules are cheap and readily available. That dose is not far from the various "official" recommendations (which are all over the range of the hundreds, depending on country). There are no known side-effects at that level.

> Secondly, the 8k dose doesn't seem realistic historically. Is there any diet that does not include the products of modern tech, that gets anywhere near those levels consistently? Doesn't seem likely.

Because historically most vitamin D intake didn't come from diet, but from sunlight exposure. Varying widely depending on how much skin you're exposing, the color of your skin, latitude, season, etc., estimates of vitamin D hourly vitamin D synthesis can be on the order of tens of thousands.

Diet wise no. Skin production wise, yes. Though these are different mechanisms and the body can turn off vitamin d production from the skin past a certain point.