Also, the science is starting to question the supplementation. It’s too early to tell, but one hypothesis is that it is a biomarker at the end of a pathway and not at the beginning of it, i.e. as a consequence of a proper diet and sunlight, and not a cause of a healthy system.
An analogy would be the analysis of car exhaust, finding certain levels of CO2, and trying to fix cars with "bad exhaust" by throwing more CO2 into the intake (except maybe this would even have a negative effect by hindering combustion).
This is an hilarious (and fitting) analogy for nutrition sciences.
Reputed and trustworthy citations from scientific sources required, please.
Industrial production of vitamin D3 irradiates the 7-dehydrocholesterol extracted from sheep's lanolin with UVB light.
There is some question as to whether ergocalciferol--a chemical mainly found in fungi that produce ergosterol and have been exposed to UVB light--is biologically equivalent to cholecalciferol in humans. It can alleviate vitamin D deficiency symptoms, but it is not known with certainty whether it can produce a sufficiency. As far as I am aware, the known cases of hypervitaminosis D have resulted from ergocalciferol supplementation, rather than from cholecalciferol.
If you are supplementing with vitamin D3, the chemical you are consuming is identical to that produced in your skin under UVB irradiation. There is no evidence whatsoever that it is destroyed in or poorly absorbed by the human digestive system. If you swallow 15000 IU of vitamin D3, that is the equivalent of standing shirtless in temperate midday sun for 15 minutes, after which time you will achieve no further benefit until some time has been spent absorbing the cholecalciferol and replenishing the 7-dehydrocholesterol in your skin.
It is poorly known, that if you have to preface a statement with "it is well known", what follows is less likely to be "known" than "unattributably rumored".
"Gravity is real."
"Reputed and trustworthy citations from scientific sources required, please."
You can get less and less ridiculous from here ad nauseam, but the point is made.
https://www.theguardian.com/science/2018/mar/09/is-vitamin-d...
And those studies saying otherwise have been backed by a lot of questionable money: https://www.nytimes.com/2018/08/18/business/vitamin-d-michae...
Oh by the way sunscreen is terrible, it doesn't have a proven link to reducing cancer and it destroys reefs so do yourself a favor and get more sun without all the slimy goop so you can feel better AND save the planet!
[1] https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-h...
The Mayo clinic article says:
> Taking 60,000 international units (IU) a day of vitamin D for several months has been shown to cause toxicity.
So 10,000, while it's well above the "recommended" dosage, is nowhere near the toxic level. Although when I was looking around the toxic level was 20,000, still, I've seen no guidance regarding Vitamin D that suggests 10,000 IUs/day can be toxic. (Especially if your BMI is over 25, and you're not getting much sunlight.)
A hypothesis exists that increasing vitamin K consumption in proportion to the vitamin D, and restricting calcium intake, would eliminate the main symptoms of excessive vitamin D supplementation. Nonhuman animal experimentation confirms, but it has not been tested in humans (likely due to the obvious ethical concerns).
Vitamin D, vitamin K, and calcium are all related.
I have seen guidance specifically for vitamin D2 (ergocalciferol), indicating that adverse symptoms may be observed at lower levels of supplementation than for vitamin D3 (cholecalciferol), but it was quite some time ago, and I don't know if the claim was confirmed or refuted scientifically.
10,000 IU is only 1.25 mg, and vitamins aren't well regulated. It's not like you'd notice if your supplement contained 100,000 IU.
http://www.usp.org/verification-services/verified-mark
Others include NSF, UL, and consumerlab
https://www.consumerreports.org/vitamins-supplements/what-us...
There's still the chance that a manufacturing mistake could result in bad dosage but that applies to all products including medicine.
http://cphpost.dk/news/danish-health-authority-warns-of-toxi...
This is in cloudy wintertime Seattle. In sunny times it may be completely unnecessary.
Now I try to get my vitamin D through more normal sources by eating lots of UV-exposed mushrooms, salmon, and sardines. Plus side is these foods are all quite healthy even without the vitamin D
The problem with vitamin D was that up until about a year ago, official recommendations in many countries were mistakenly low (500-1000 IUs), which as it turned out, was not enough for many people. It was even hard to find proper pills that has high enough dosages, because when you got to your local farmacist which was going by the official recommendations, all they had were 200-500 IU pills, because they were not expecting that anyone would need more. So as an average citizen who does not do their research properly, if they just went into a farmacist and took the first Vitamin D supplement they saw, the chances were that they were getting one which had basically no effect.
When the dosage is right, many people experience positive effects and dormant Vitamin D levels really do go up. The sun is not required.