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Comment by enlyth | Hacker News Reader

I take Vitamin D in the winter anyway because there's not enough time to get sufficient sun exposure, especially here in the UK.

From what I've read hypervitaminosis D is quite hard to achieve, so I don't see the harm in taking it.

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Hypervitaminosis D is hard to achieve _by sitting in the sun_ because then your body makes as much as it needs and then stops making any more.

It is not hard to achieve when taking supplements, because you can always stuff yourself with way more supplemental vitamin D than your body can clear up before it starts causing problems.

Source: I was prescribed vitamin D3 by my endocrinologist (it's actually officially a hormone, cholecalciferol). I had regular blood tests for a year or so (for reasons) that were monitored by my endocrinologist, then at some point she told me to stop taking the D3 vitamin supplements because the amount of D3 in my blood was reaching the upper limit of a healthy person's. I too live in the UK.

It still took you a year at prescription level doses, though. The risk of anyone doing it on a typical over the counter dose is close to nil.

400IU of Vitamin D per day in winter is an official NHS recommendation for _all_ adults: https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-.... For darker skinned people, the recommendation is year-round.

It's the serum level of activated vitamin D that matters, not your intake which may not even be absorbed properly. (You need to have sufficient magnesium for instance).

That there will be large variations in outcome is indicated by this conclusion from Nutrients 2020, 12, 1268

In 238 healthy adults (18-64; 50% male,female) screened for serum 25-OH-VitD concentration "two months of treatment with 25 µg (1000 IU) daily was not sufficient to assure recommended serum 25-OH-vitD levels in all subjects"

Since covid hit I wasn't really going outside that much.

I was taking 2500 IU daily since September. Got tested in December and had 102 nmol/l. The conservative reference is > 75 nmol/l and newer ones are 100-150 (https://www.grassrootshealth.net/document/vitamin-d-dose-res...). So even with 4+ months of taking 2500 IU I was on the lower end of the reference.

The values are always very individual, both in terms of uptake and varying production qualities.

I'd suggest people check their values every other month or so to make sure their values aren't too high.

Especially those taking higher grade units, some pills are >5000iu.

Isn't high value for Vitamin D not a problem? Human body can deal with too much Vitamin D by storing it efficiently.

https://en.m.wikipedia.org/wiki/Vitamin_D_toxicity Whilst overdosing is hard, its not impossible. There is no such thing as storing vitamins, or in fact, any nutrients _for free_.

Edit: am I wrong? Ingesting too much fat will be bad for one's health, ingesting too much carbohydrates, minerals, protein will be too. The same goes for any vitamins. There's no _efficient way to store anything_ if you ingest too much of it.

Can't say about them all, but Vitamin A could be stored in the body for like half a year after taking high dosage supplements. Of course, there is a limit, much higher dosage are harmful (the widely known polar bear liver toxicity as example).

This does not apply to all of the vitamins and is more of a special case behavior for Vitamin A.

Generally water soluble vitamins have low retention time while fat soluble vitamins have high retention and are riskier to supplement.

Vitamin D is fat soluble.

It can lead to kidney stones.

Everything leads to kidney stones, it seems.

>> I'd suggest people check their values every other month or so to make sure their values aren't too high.

I recently spoke to my GP about this and was told they don't usually bother testing people for Vitamin D levels in the UK because most of us would be deficient. She recommended supplementing (I believe 4000 IU) all Winter and suggested possibly continuing throughout the entire year.

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