Highly doubt 5k IUs is the issue. Some select quotes from "Vitamin D Is Not as Toxic as Was Once Thought: A Historical and an Up-to-Date Perspective" by Michael Holick in Mayo Clinic Proceedings [0]:

> Ekwaru et al recently reported on more than 17,000 healthy adult volunteers participating in a preventative health program and taking varying doses of vitamin D up to 20,000 IU/d. These patients did not demonstrate any toxicity, and the blood level of 25(OH)D in those taking even 20,000 IU/d was less than 100 ng/mL.

> 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).

[0]: Holick, https://www.mayoclinicproceedings.org/article/S0025-6196(15)...

[1]: Ekwaru et al, https://pubmed.ncbi.nlm.nih.gov/25372709/

[0] is an editorial and [1] seemingly went unpublished, other than in PLOS One, which means it goes through a very different peer review process than most other journals (that is, no peer review on its content, only on its methodology).

The "tolerable upper limit" for vitamin D is set absurdly low.

I have perused the literature on D toxicity and each case involved someone taking at least 100k IU per day, and usually way more than that. I take 50k IU per day every winter and have never had an issue. Blood calcium levels normal, etc

5k IU is an average dose and will absolutely not cause harm.

> "I have perused the literature"

...and you are?

> 5k IU is an average dose and will absolutely not cause harm.

This is wildly irresponsible to post, and should be removed from HN.

>...and you are?

Someone who is wholly uninterested in the credential theory of epistemology. Back to reddit with that, please.

> This is wildly irresponsible to post, and should be removed from HN.

You don't seem to know what the TUIL actually means. The tolerable upper intake level of a substance is not the actual safe upper limit, it just guarantees that a certain level is safe. In the case of vitamin D, the actual safe upper limit is likely an order of magnitude higher, which was even acknowledged by the people who, very conservatively, set the TUIL at 4k IU.[0] If 4k IU is completely safe (which it is), then there is nothing at all irresponsible about suggesting that 5k IU is completely safe (which it is), unless that extra 1000 IU somehow accomplishes some deleterious effect, which it doesn't.

That extra 1000 IU between 4k and 5k is simply insignificant. To put all these numbers in context, the body synthesizes the equivalent of anywhere from 4k-12k IU per day from sunlight,[1][2] and possibly 20k+ IU if you're sunbathing with most of your skin exposed.[3] So really, a 5k dose is in the low to moderate range. If 5k IU of vitamin D is scary or irresponsible, then getting even a little sun exposure is really scary and irresponsible!

[0] https://pubmed.ncbi.nlm.nih.gov/17209171/

[1] https://doi.org/10.1093/ajcn/61.3.638S

[2] https://doi.org/10.1016/j.jaad.2007.03.004

[3] https://pubmed.ncbi.nlm.nih.gov/18290718/

> Someone who is wholly uninterested in the credential theory of epistemology.

So nobody qualified to answer this question? That's what I expected. In medicine more so than in nearly any other field, qualified experts should be the only people to express opinions publicly, considering the potential negative outcomes.

You really shouldn't be giving medical advice on any website, Reddit or Hacker News. This is on the same level as anti-vaxx shit, I hope you realize.

This, more than Reddit, is a place where qualified people discuss topics. If you'd like to wildly speculate, that sounds more like what happens on Reddit.

Are you sure? 5k being a safe average dose seems to be corroborated across the internet and the abstracts of some papers I've seen.

And yet, not a single reputable journal will publish those papers, the medical community won't change the recommendations, and those studies go unreplicated.

It seems like there's an undereducated underground on the Internet that has the hubris to think they know more than the medical consensus, so what you're seeing are the effects of that hubris, nothing more.

Turns out Vitamin D is the anti-vaxx of computer nerds. Pretty hypocritical, but unsurprising.

That assumes your body is absorbing all of it. I suspect a lot of people's aren't, hence the high doses. I have found for example that 1000iu in the form of drops under the tongue has dramatically more effect than 1000iu in the form of a chewable tablet.

Those numbers are wrong by an order of magnitude, because the original estimation was based on faulty math. The actual dose needed to bring serum levels up for most people would be far higher.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4210929/

I'm going to go ahead and trust Harvard Medicine over a single study that has since gone largely uncited, and was published in "Nutrients" which carries an h-index of 115 (Nature, for example, carries an h-index of 1226) [0][1].

[0] https://www.scimagojr.com/journalsearch.php?q=19700188323&ti...

[1] https://www.scimagojr.com/journalsearch.php?q=21206&tip=sid&...

You should never judge an article by where it was published (some exceptions of course), only in the quality of the work. Impact factors are loosely a measurement of significance of the work, in terms of how broadly applicable they are to the fields of science. It is absolutely not a strict measure of the expected quality of the article.

Also, for what it's worth, most of the articles referenced in the Harvard Medicine review referring to dosages are from before 2010, so they may be out of date.

And why should I trust you? You've given a decree, "Thou shalt not judge a paper based on where it was published!" and then don't give any reasons why that would be the case.

Also, I'm not qualified to judge a paper by its work quality, I need to rely on the experts in the field for that, and a decent proxy for that judgement is where a paper gets published, so by looking at where a paper was published, I am judging a paper by its quality.

Sorry, I thought my reason was clear from my comment. I did not intend it as a decree you should follow blindly. I’ll expand on my explanation.

Impact factor is not a measurement of an individual article’s quality. It is a summary statistic, a rough measurement for how frequently that particular journal gets cited in other journals.

By judging an individual article by the impact factor of its journal, without reading the article and determing its quality yourself, you bias yourself to whatever those results might be one way or another with a statistic not intended to relay any information about the journal article itself.

You are right that it is a decent proxy where higher impact tends to have better journal quality (anecdotal, but I have observed this for sure) but I got annoyed when you claimed an article published in a low impact journal had no merit. That is simply not the case.

You can have the best, high quality scientific study ever about a highly specific thing, but because it is so specific you won’t have the broad impact that would get into one of the top tier journals. But with your viewpoint, that study would get thrown out the window.