https://news.ycombinator.com/user?id=devaboone

And she's done a series on it:

https://www.devaboone.com/post/vitamin-d-part-1-back-to-basi...

In absurdly high doses, sure. The Institute of Medicine certifies 4,000 IUs as the upper safe daily limit, although doctors will prescribe higher doses for people with a Vitamin D deficiency.

The Mayo clinic did a study of Vitamin D levels in 20,308 people across 10 years. The result was that 8% of people had Vitamin D levels higher than 50ng/ml (typically a sign of Vitamin D toxicity) but found no correlation between those levels of Vitamin D. They found one, one person out of 20k, who actually displayed symptoms of Vitamin D toxicity. Their blood levels of Vitamin D were over 350ng/ml. They had been taking 100k IUs (25x the suggested dose) as a routine daily supplement. I can only find one reported death from Vitamin D overdose, and it was a 10 year old boy who was mistakenly given 600,000 IUs of Vitamin D a day instead of growth hormone by a hospital in 2015.

Let's compare that to Tylenol (acetaminophen). Tylenol contains 500mg of acetaminophen. Maximum suggested daily dose is 8 tablets, so 4g. 25 times that is 100g. So someone abusing tylenol as hard as that person abused Vitamin D would be consuming 100g of tylenol a day. Medical literature suggests that you go to the ER immediately if you consume over 10g of acetaminophen. Of people who hit blood levels requiring treatment, 5% die and 58% have severe liver damage as a result. I can't find a good, easy correlation between the blood levels requiring treatment and amount taken, but I'm going to go out on a limb and guess that taking 200 Tylenols puts you there.

So if we compare the risk, relatively, Vitamin D requires you to take over 150 times your maximum daily dose for an extended period of time (dosing for children is lower than adults) to cause death. If you take 25x the amount of Tylenol once, there's a good chance you die or have severe long term outcomes.

Vitamin D is amazingly safe, provided you treat it like a medication and don't randomly swallow fist fulls of the capsules. Many people in the US (and some parts of Europe, especially in the north) should actually already be taking a supplement. Low Vitamin D levels are exceptionally common now. In the case of the US, obesity causes low Vitamin D levels, not going outside often enough causes low Vitamin D, and not eating foods containing vitamin D causes low Vitamin D. That's a disease practically tailored to our obese, couch-bound, junk-food inhaling residents. In northern Europe, I think they largely blame the seasonal changes in daylight patterns.

I'm all for calling out danger, I just don't see any here. I don't doubt that some people will manage to hurt themselves. I can already hear someone thinking "if 4,000 IUs keeps me a little safe, I can take 1,000,000 IUs and not wear a mask". If we're really that concerned that someone will harm themselves, we should be able to just add Vitamin D to the tracking system we use for Sudafed. Don't let anyone but more than 10k IUs per day. That's enough for 2 adults and a child at healthy doses, but low enough that taking that much every day is unlikely to harm you in the immediate future (and doesn't seem to be likely to harm you at all, but it is above the suggested dose).

"with appropriate messaging"

And, also, you're talking about one expert opinion, perhaps this person doesn't live at 41 degrees south where our both too cold and too dark for half the year or more to get enough sun exposure and peoples diets are often quire poor.

That's why we need to look at the data in aggregate, and have localities / states set their own guidelines and encourage / incentivise doctors to do more testing and symptom analysis.

Also there's some Joe Rogan-esque "just take the 5000 IU bro" even though 4000 is the recommended supplement upper bound. And devaboone warns against even using that much.

For breastfed babies, France recommend an intake of 25µg to 30µg but it's half of that in the UK (8.5 to 10µg).

It is basically wasteful, only in extreme cases you could 'overdose' vitamins.

https://en.wikipedia.org/wiki/Vitamin_D_toxicity

This is not true. Vitamin D is fat-soluble, not water-soluble. Your kidneys can only filter out water-soluble vitamins. B vitamins are water-soluble; that's why there's practically no upper limit to how much you can take. Your kidneys will filter out the extra (assuming you aren't eating buckets full of the stuff).

Vitamin D toxicity occurs specifically because your body can't remove the excess vitamin D stored in your fat.

That's also why severe overdose happens over time, as opposed to instantly. You have to take a huge amount of Vitamin D at once to overdose (like millions of IUs) but you can cause toxicity using smaller doses over longer periods of time. If your body could flush it out, that wouldn't be true. Any excess would be removed and you would start each day "fresh".

Many over-the-counter vitamin D supplements appear dosed for people with problems absorbing the chemical.

Not really. It depends on the person obviously but the recommended values are too low due to statistical errors.

Up to 4000 iu per day likely ok.

Both are very far below the 4000 that's often cited here. So I think that 4000 is not a recommended intake but a limit before it becomes risky. For normal people it doesn't make sense to then aim for that maximum dosage.

One thing to consider is biological inefficiency. A 4,000 IU capsule contains 4,000 IUs, but that doesn't mean your body can't actually extract all 4,000 IUs.

That said, I think 1k IUs is considered a standard dose for people without a deficiency. 4k IUs are generally used by people who are currently deficient, or have other issues that cause the deficiency. Doctors will sometimes prescribe doses up to 10k IUs for deficient people.

200 iu sounds very low.

Note, the Endocrine Society currently suggests a minimum 25(OH)D level of 30 ng/ml (75 nmol/liter) and suggests much higher levels of supplementation if you need to raise it: "to raise the blood level of 25(OH)D above 30 ng/ml may require at least 1500 –2000 IU/d of supplemental vitamin D."

Holick, Michael F., Neil C. Binkley, Heike A. Bischoff-Ferrari, Catherine M. Gordon, David A. Hanley, Robert P. Heaney, M. Hassan Murad, and Connie M. Weaver. “Evaluation, Treatment, and Prevention of Vitamin D Deficiency: An Endocrine Society Clinical Practice Guideline.” The Journal of Clinical Endocrinology & Metabolism 96, no. 7 (July 1, 2011): 1911–30. https://doi.org/10.1210/jc.2011-0385.

It's also worth noting that studies have shown that without sun exposure, people may require even higher levels of supplementation to maintain their 25(OH)D levels:

Heaney, Robert P., K. Michael Davies, Tai C. Chen, Michael F. Holick, and M. Janet Barger-Lux. “Human Serum 25-Hydroxycholecalciferol Response to Extended Oral Dosing with Cholecalciferol.” The American Journal of Clinical Nutrition 77, no. 1 (January 2003): 204–10. https://doi.org/10.1093/ajcn/77.1.204.

"CONCLUSIONS: Healthy men seem to use 3000-5000 IU cholecalciferol/d, apparently meeting > 80% of their winter cholecalciferol need with cutaneously synthesized accumulations from solar sources during the preceding summer months. Current recommended vitamin D inputs are inadequate to maintain serum 25-hydroxycholecalciferol concentration in the absence of substantial cutaneous production of vitamin D."

I think this winter I will run an experiment on myself.

It's a pretty useless one in this case. Old people are much more likely to have vitamin D deficiency. They are also more likely to die of COVID. The low vitamin D is a marker of frailty, not a cause.

This was not simply observational. There will be no correlation between being given higher dose vitamin D and age in this trial, the results appear at first blush to be showing Vitamin D is working independant of age.

By the by this /exactly/ why a randomised trial has been the gold standard for medical treatment for so long. False correlations, confounding factors etc are all vastly less likely to skew the results. 2 groups chosen at random, nobody in the groups or treating them knows which is which. 1 group given treatment, 1 given a placebo. How much difference do we see in the 2 groups as a result of treatment.

It's a good question. It's always worth asking. It's always worth checking. The rabbit hole of stat analysis of treatments goes pretty deep from there. Ethical issues come in. Expense. But we all need to make the effort to understand it on some level or we're marks for snake-oil.

To put this in perspective: I take 800iu as a maintenance dose to keep my vitamin D levels up. (I'm doing this under a doctor's supervision: I've been sick with low levels and she does blood tests occasionally to be sure). 2 eggs is simply not enough.