Hacker News Reader

Comment by derefr | Hacker News Reader

Mind you, what was previously (and mostly still is!) considered “high doses” of vitamim D are actually closer to the RDI than the doses anyone is taking. The RDI for vitamin D was miscalculated as 1/10th its proper value decades ago, and this error was only recently corrected: https://www.sciencedaily.com/releases/2015/03/150317122458.h...

So when a science journalist—or even most scientists still—say “high doses” of vitamin D, they really mean proper doses of vitamin D. Including in this article! They’re quoting the same improper 600IU RDI standard that the article above refutes, and quoting 4000IU as an abnormal amount rather than being perfectly-well-within the correct RDI value.

View on HN

> Mind you, what was previously (and mostly still is!) considered “high doses” of vitamim D are actually closer to the RDI than the doses anyone is taking. The RDI for vitamin D was miscalculated as 1/10th its proper value decades ago, and this error was only recently corrected:

No, there is a paper claiming that it was miscalculated and should be corrected (and, as another comment notes, there is a later paper calling for a reduction rather than an increase.) The actual current numbers remain (for most age groups):

Estimated Average Requirement: 400IU/day

Recommended Daily Allowance: 600IU/day

Tolerable Upper Intake Level: 4000IU/day

A paper calling for a change in the RDA is not a change in the RDA.

Why are most sold supplements in the 3000-5000UI range?

I don't think they are, though there certainly are supplements in that range and higher.

But supplements don't mostly sell based on either science or government recommendations, but fads which are often unrelated to either.

Vitamin D is fat-soluble and can be stored in body fat. Supplements in the higher range are meant to be taken once a week or once a month. Supplements in the 400-1000IU range are meant to be taken daily.

Vitamin D is fat soluble and isn't cleared by the body as quickly as other vitamins such as B. Therefore it can be taken in higher doses, but less frequently. This is often done for convenience sake. A 3000-5000IU pill every week is easier to remember than a 500-600IU pill every day.

I'm on mobile at the moment, but I think there is more than just one paper suggesting that Vitamin D RDI is too low, even if they don't explicitly call for raising the official level?

I can dig for links when I'm back at a Desktop.

I was referring to the one paper cited in the thread, which was being misrepresented as an actual rather than recommended increases to the official RDA. Yes, there have certainly been more than one paper suggesting that higher Vitamin D intake than the current RDA is desirable, but they have not resulted in the RDA being raised as suggested upthread.

What? There are doctors that are prescribing 2000IU+ daily. I have vitamin D supplements with 2000IU per pill.

I've read lately about multiple papers that propose multiple k of IU per day.

> There are doctors that are prescribing 5000IU+ daily

What doctors prescribe based on the actual conditions particular patients exhibit (and, at doses that high, often with serum level monitoring) is only distantly related, even in theory, to population-wide recommendations like the RDA.

> I've read lately about multiple papers that propose multiple k of IU per day.

Yeah, so have I, and I personally think (though I’m not an expert in this field) it's likely that the RDA is way too low. But there's a difference between the belief that RDA should be higher and the claim that the RDA has, in fact, been raised. It has not, it's still 600 IU/day.

Doctors may be making those recommendations based on blood tests indicating specific patient deficiencies. As you note, though, research does at least suggest daily vitamin D supplementation in the thousands of IUs per day range may be considered safe.

I'm not a doctor, but I believe if you've been directed by one to supplement vitamin D, blood tests probably should have preceded that recommendation.

I've had one doctor prescribe me 10K a week. Another one recommended no more than 400/day.

Doctors do not agree. Some have jumped on the bandwagon, and others believe it is just a bandwagon.

I was told to take 20,000IU/day, just to be sure. It might be just correlation, but it helped with the issue I had.

Interesting, because a paper was released early last year that reduced the RDI for vitamin D by about 1/2

"After re-measurement of vitamin D by improved technology, the Recommended Dietary Allowance (RDA) for vitamin D intake drops from 800 to 400 International Units (IU) per day, new research reports."

https://www.sciencedaily.com/releases/2017/04/170403083103.h...

Note the caveat at the end:

> "Remember, this RDA is for bone health only," Gallagher cautioned. "It may be different for other diseases. Although trials looking into cancer, diabetes, and other diseases are ongoing, we do not have information about this yet."

The actual RDA for Vitamin D is set based on bone health, since there is not sufficient data for other conditions it may effect, so that's not a significant caveat when it comes to a recommendation to change the RDA.

The RDI baseline is always set to bone health. It's an indicator for the general population, not people with illnesses that may increase their RDI amount.

Except Vitamin D influences more than just bone health, and the recent research suggesting we should increase recommended dosages has centered on that.

No, it reduced what the same authors recommended the RDA should be based on the same researchers previous work by half, but that's only a reduction by a third from what the actual RDA is.

Please read the study. They tested at what the earlier study listed as a "correct" level of Vitamin D, and the tests showed that the lower amount was correct.

"The participants were randomized to one of seven vitamin D3 doses: 400, 800, 1600, 2400, 3200, 4000, 4800 IU/day or placebo, for 1 year, and all the women were given calcium supplements to maintain a total calcium intake."

> Please read the study

I did. The earlier study cited recommended the RDA should be 800, this study recommends 400; that cuts it by half from the earlier study.

The actual government issued RDA, now and at the time of the study, however, is 600, not 800, so it's only recommending the actual RDA be reduced by 1/3, not 1/2.

2017 (relies on earlier studies cited.) The Big Vitamin D Mistake https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5541280/

In terms of importance in interpreting this result, this comment should be the top-voted, top-level comment.

Reply on news.ycombinator.com