The issue I've found with these discussions is it appears there's mixed evidence on if vitamin D *supplementation* actually has a positive impact, regardless of vitamin D deficiency. In other words, is the deficiency causal or correlative.
I have no opinion on the matter, and am inclined to think there is at least some positive benefit. But YMMV
I took 10k iu via a multivitamin for a few months, and ended up with Vitamin D levels 5x higher than the maximum on the labcorp reference range. "Vitamin D toxicity"
It took many months to get the levels back to normal. Vitamin D is one of those things that once you overdose, it takes many months for the levels to slowly come down after you stop supplementing.
Be careful with Vitamin D!
The downside to having high levels is plaque/calcium deposits in arteries, if I'm not mistaken. Which can be mitigated by taking K2.
Are you aware of the history of setting acceptable levels of Vitamin D? Basically, 100 years ago, people experimented with cures for TB by giving patients one to two orders of magnitude higher dosage than the "vitamin D toxicity" levels reported today. Like insanely high numbers. Strangely enough, most people did recover from the TB, but they kept getting the treatments anyway, and that in a few instances led to bone issues. So for some reason that doesn't seem to be documented, they set the "safe level" of vitamin D to be something like two orders of magnitude lower than the level that actually caused issues. And that level has never been changed.
All of the studies I've seen around Vitamin D supplementation has shown that the "safe level" reported today is way, way lower than it should be. People appear to be just fine taking 10k IUs for months on end, even 7 years in one study. I think what we're learning is that the "safe level" is a very wide spectrum; some people could possibly be harmed from a low level, whereas some people are perfectly fine at a very high level.
And, fixed dosage never makes sense with Vitamin D. If you're supplementing, you need to make sure you regulate it based on sun exposure, since it's literally the Sun vitamin.
It's easy to double up if you decide to eat lunch outside because the weather is nice this month. I take 10k only if I'm indoors all day, and reduce or take none if I'm out.
> An excess of vitamin D causes abnormally high blood concentrations of calcium, which can cause overcalcification of soft tissues, including arteries and kidneys. Symptoms appear several months after excessive doses of vitamin D are administered. A mutation of the CYP24A1 gene can lead to a reduction in the degradation of vitamin D and thus to vitamin toxicity without high oral intake (see Vitamin D § Excess).
> Treatment
> In almost every case, ceasing vitamin D intake, combined with a low-calcium diet and corticosteroid drugs, will allow for a full recovery within a month. Bisphosphonate drugs (which inhibit bone resorption) can also be administered.[2]
Regardless, blood levels need to be checked for this sort of thing and doses are not one-size-fits-all. I also once was taking 10k daily, for several months, and ended up just barely in excess territory with no noticeable symptoms. (I settled on taking 4k daily in the long term.)
> In almost every case, ceasing vitamin D intake, combined with a low-calcium diet and corticosteroid drugs, will allow for a full recovery within a month.
Surprised to see just 4 weeks for a recovery. I got retested after 8 weeks (only minor improvement) and wasn't until 16 weeks until the test finally came back in range.
100% no dose is one-size-fits-all. I overdosed from taking a specialty multivitamin (it has a discord channel and everything). So was chatting with people taking the same vitamin, same dosages, also getting tested, but others had no issues at the same doses.
I guess I just absorb vitamin D with great efficiency, who knows.
Echo this with a PSA: it's a simple test to get your levels, and I'm a proponent of ensuring it's included when you have other regular blood tests (may have to ask for it). That can allow a person to see patterns, how effective any supplementation (and different amounts) are, etc.
I can use myself as an example: I have crohn's disease and I can take doses of 50000UI for some weeks, then 4000UI daily and after a year have my Vitamin D results as low as 20ng/ml.
The point wasn't the dose, I just picked a number out of my ass.
The point is that from that N IU the 100 people will absorb anything from 0-N, it's very individual and varied.
The only way to be sure is to test your levels, which costs money every time. There really should be a simple and cheap home test kit for it. You'd sell millions every year just in the Nordics and Canada =)
Maybe this comes across snide, but have you been to the Nordics? I can get tested at my GP for free practically as often as I'd like, I doubt you'd sell too much in the way of home test kits.
There is no way that's what they meant. 50k is an absurdly large dose that's way outside the safe intake range. 10k is used sometimes under medical supervision and even then it's a very short term measure. For long term intake, 4000IU is a widely accepted safe upper limit. 50k is an order of magnitude more than that.
There's plenty of documentation of people taking 50k for a period of time and having no side effects. There's been something like a dozen trials using high doses like this to treat TB, and they're usually successful, with no significant negative symptoms.
Conversely, some studies have shown that 4k IU does contribute to hypercalcemia in a small number of cases (4 per 1000). So actually 4k is deemed "not completely safe" as a limit.
The point is, the amount you take needs to be adjusted by a clinician, as the safe range for you is unknowable otherwise.
If your doctor is not seeing results they’ll keep upping the dose and I’ve heard of some that sound like an attempt at assisted suicide. Most of us would get toxicity from some of the ones I’ve heard.
My family is in this group. We are poor absorbers of vitamin D, some of my elder relatives need 5 times the "safe upper limit" to have healthy blood levels. As long as you're checking your blood values routinely (and for both D2 and D3, not just one or the other), it's reasonably safe. Sort of like other prescriptions in general.
I heard about a guy who ordered a bottle and ended up with vitamin D poisoning, on one of those Ira Glass style podcasts. Turns out they forgot to compound it before sending it out so he was getting “cask strength” vitamin D. Sounded very unpleasant.
Most of the vitamin D supplement studies have been very low quality in that they give all subjects in each group a fixed amount (or placebo). Ideally they should periodically test blood levels and titrate the dose to hit a target range. This would get us closer to establishing causality (or lack thereof) including a response curve. The amount needed to hit a given target will be wildly different for many individuals based on factors that are still not well understood.
Just my results (n=1) and I don't think this is exactly what you were saying, but just in case other read it the same way I did at first: having had (lab tested) vitamin D deficiencies, vitamin D supplementation can help to restore levels back into the desired range. So supplementation can have the desired effect of improving vitamin D levels (more below). It is a simple test that most doctors don't quibble about adding on to other blood tests (i.e. during annual checkup, for instance), but isn't generally checked by default. (note: insurers may want it to be "diagnostic" rather than "preventative" in order to cover the test.)
Whether it has a "positive impact" on overall health (which I believe to be your point), that would be even more anecdotal and also impossible for me to narrow down whether that one factor had any significant effect, so I won't posit that. And I agree that from different studies I've read, the actual science on it is pretty varied and I haven't seen anything conclusive. Even this study notes their conclusion was "... among adults with suboptimal baseline vitamin D levels".
This is solely my own anecdote, but I used to get bad seasonal depression every winter. I tried a number of interventions short of medication; none moved the needle very much. I started supplementing with vitamin D probably 8 years ago and haven't had any issues with seasonal depression since.
I'm pretty personally convinced that it was the supplements that helped here.
I was put on prescription vitamin D2 50000 IU and it caused a bunch of side effects for me including heart palpitations for over a week and then a paradoxical reaction to magnesium causing them to be even more intense.
Proceed with caution and listen to your body. Doctors were accusing every other thing than accepting whatever it did to my calcium / other electrolytes bothered my heart.
It's expensive in the US because one company has exclusive sales here (patent protection?), but you could try calcefidiol, weekly dose and is supposed to get levels up rapidly. Apparently it's the common form to take in Spain, and it's further down the metabolic pathway vs cholecalciferol. (I take but still have to get levels checked)
I took a blood test several weeks ago, my Vitamin D level was 14 ng/ml. I was so fatigued there were times I had to lay on my office floor because I didn't even have the energy to sit in my chair. I started taking 50k IU's weekly and then 10k IU's daily, and the results were dramatic. I went from having 0 energy to nearly normal. I also had soreness in my legs which went away.
I have no opinion on the matter, and am inclined to think there is at least some positive benefit. But YMMV