
Vitamin D: the New Covid-19 Chloroquine? - chl
https://berthub.eu/articles/posts/vitamin-d-the-new-covid-19-chloroquine/
======
trevorkoob
Did my masters on Vitamin D - It is very difficult to extract CLINICALLY
RELEVANT information from retrospective epidemiological studies.

However, there a a few things that are clear:

1\. Calcium absorption from the intestine increases with vitamin D
supplementation dose up to around 8-10,000 IU D3 daily.

2\. 15 minutes of full body exposure in noon sun is equivalent to a dose of
~20,000 IU D3

3\. There are few cases of vitamin D overdose in the literature - doses in the
1,000,000 IU+ range within days is generally where symptoms are noted - this
excludes people with kidney disorders.

Personally, I take 10k IU D3 a day. The D3 is important because D2 has 1/2 to
1/3 the effect per dose in raising calcium absorption levels.

I would recommend this level of supplementation to anyone who doesn’t have a
kidney disorder.

~~~
elric
Re #2: the figure gets thrown around a lot. But who is outside, naked, at noon
for fifteen minutes? It's really hard to translate that to anything meaningful
or actionable.

Here's a tool that can help calculate useful exposure depending on your
location/time of year. Doesn't take clothing into account however..

[https://fastrt.nilu.no/VitD-
ez_quartMEDandMED_v2.html](https://fastrt.nilu.no/VitD-
ez_quartMEDandMED_v2.html)

~~~
travisoneill1
The point is that being outside naked at noon every day for 15 minutes
wouldn't hurt you. Therefore, a daily dose of 20,000 IU / day won't hurt you.
Therefore, a 5000 IU supplement every day won't hurt you either.

~~~
Barrin92
is this just an extrapolation or does my body actually constantly produce the
same amount of vitamin D if i sit in the sun even if I don't have a deficit?

Because usually phisiological processes are in some kind of equilibrium and
regulated, so it's not straightforward to compare it to supplements.

~~~
trevorkoob
7-dehydrocholesterol is photolyzed by UV to previtamin D. There is then
spontaneous isomerization between this previtamin D, vitamin D and 2 inactive
isomers. As vitamin D is used by the body, and the inactive isomers remain in
the skin, there is an equilibrium - as vitamin D is used by the body it is
drawn from the skin, leading to more conversion of inactive isomers to active
vitamin D.

------
watertom
Since I was a child I’ve been a walking respiratory illness machine.
Bronchitis, sinusitis, flu, pneumonia, common cold, etc.

During “flu” season I was usually sick for the entire season with a rotating
assortment of viral respiratory issues, this lasted until about 7 years ago.

8 years ago in September I started taking 10,000 IU of vitamin D3 and 180mg of
K2 daily.

I haven’t had a deputies illness since. My children were getting sick at their
normal clip, my wife the same, but not me. I went from being sick all the time
to not getting sick ever. I made one change in my life, adding the D3 and K2.

After 2 years of not getting sick my wife and children started supplementing
with D3 and K2, everyone stopped getting sick. My son went off to college and
stopped taking the D3 and K2 and during the winter semester he got sick twice,
he had me sent him the D3 and K2, he hasn’t been sick since.

It’s a small sample size, but even at 10,000 IU daily D3 is not dangerous or
expensive, the only caveat seems to be that you need to supplement with K2 or
you can cause gardening if the arteries due to calcification.

My doctor thinks it’s a lot of nonsense, but then again he wants every patient
on blood pressure and cholesterol medication “just in case”.

~~~
tomtomistaken
I had anxiety attacks and back pain for years. Maybe it’s just a weird and
strong placebo effect, but after starting to take vitamin D these things were
simply gone.

~~~
arethuza
I found the same - I was starting to get anxiety first thing in the morning -
started taking Vitamin D and it simply stopped. At the time I had no idea that
Vitamin D could have that effect.

------
tomhoward
All these articles about different individual nutrients start to feel like
heath whack-a-mole.

How about this: to be in the best possible position to beat any serious
infection, you need to be in generally good health.

That means having adequate levels of all essential nutrients - i.e., all the
vitamins, minerals, amino acids, enzymes etc that you get from maintaining a
good diet and healthy lifestyle over the long term.

To focus on just one nutrient as a pandemic looms just isn't the answer; it's
not how health works.

That said, I've personally researched what nutrients (note the plural) are
most important for beating an infection like this, and have adjusted my
nutrient intake somewhat, and recommended to close relatives they do the same.
But this is after I and they have spent many years researching and maintaining
good health practices.

Update: if I was in not-so-good health (and not in medical treatment for a
diagnosed condition, in which case, consult your doctor), my approach would
be:

\- boost my amino acids, fatty acids and minerals with a few spoonfuls of hemp
seeds every day

\- take extra supplements of vitamins A, B complex, C and D (and perhaps K?)

\- do plenty of walking in the fresh air and sun,

\- keep a generally healthy diet of good quality protein and veg.

Update 2: Others are mentioning Vitamin K, which seems like a good idea to
supplement if you're generally nutrient deficient, but may not be necessary if
you have a good diet. [1]

Disclaimer: not a health professional, but have had personal reasons to get
very knowledgable about health and diet over many years.

[1] [https://www.healthline.com/nutrition/foods-high-in-
vitamin-k](https://www.healthline.com/nutrition/foods-high-in-vitamin-k)

~~~
thorwasdfasdf
And, try to get those things from foods. It can't be said enough: Fruits and
Vegetables have extremely high densities of all your minerals and vitamins.
I've calculated all their densities here based on USDA nutritional info:
[https://kale.world/c](https://kale.world/c) All the results are normalized to
200 calories for easy comparison.

When you get your vitamins/minerals from a pill, you run the risk of your body
not absorbing it because that's not how our bodies adapted to absorb those
things for millions of years.

If you're eating a healthy diet (90%+ plant based whole foods), you will get
more than enough minerals/vitamins and amino acids.

Taking a few spoon fulls of hemp seeds is an excellent idea: it's super high
in magnesium which is a mineral that most of us are greatly lacking. But, I
would consider hemp seeds as just another food part of a plant based whole
foods diet. personally, i add it to salads, smoothies, etc.

And you don't need Vitamin K supplements. Greens are extraordinarily high in
Vitamin K. Even, just 20 calories of Spinach will provide over 400% of your
daily Vitamin K intake!

People, be especially careful with supplements, they're very much unregulated
and can put almost anything they want in those things.

Nature makes the best supplements: it's called food (plant based whole foods
with a variety of grains and beans, lots of vegetables and fruits and some
meat) and it has everything our body needs. Yes, for vitamin D, you'll need to
go outside and get some exposure to the sun. Actually, doctor's tell us,
Vitamin D isn't even a Vitamin, it's actually a hormone that your body makes
all on it's own with enough exposure to sun. But, based on your skin
pigmentation, you may need more or less exposure.

~~~
ekelsen
> Fruits and Vegetables have extremely high densities of all your minerals and
> vitamins.

I don't think they have B12, you need to get that from animal sources or a
pill.

~~~
thorwasdfasdf
There are mushrooms which contain B12. Or you could go with soymilk, almond
milk, etc. Those typically are fortified with B12.

People used to get B12 from the bacteria in the soil and the plants we eat.
Not, anymore.

So, yes, you could eat some meat. B12 is present in very high concentrations
in a lot of sea food.

~~~
ekelsen
Last I checked none of those things are fruits or vegetables. Suggesting they
were enough to get all necessary vitamins and minerals was simply inaccurate
and bad health advice.

When I Google "mushroom B12" it seems to suggest mushrooms have almost none.

People used to get B12 by eating meat (which I use generally to also include
seafood).

------
goda90
"Adipose tissue (“belly fat”) appears to absorb but not release vitamin D. If
we want to do some armchair hypothesizing, perhaps people historically used to
lose weight in winter, which definitely would release the stored vitamin D
just when it was needed."

This is an interesting idea. It's believed our bodies get fat to ensure we
have energy when food is scarce. It makes sense that we'd also want to have
vitamins available too.

~~~
Izkata
An addition to that: Over a decade ago (so unfortunately I have no reference,
this just stuck with me for how against common sense it was) I remember
reading that being overweight but not obese correlated with good health better
than being "normal" weight did. Their theory was that if being sick made it so
you were less hungry, you could still get an energy boost by using up fat
reserves and be able to fight off illness faster.

This sounds like a much more specific and more testable version of that
theory.

~~~
rvp-x
I assume this is a related newspaper article:
[https://www.independent.co.uk/life-style/health-and-
families...](https://www.independent.co.uk/life-style/health-and-
families/health-news/overweight-septuagenarians-live-longer-
study-5520318.html)

Important to note it refers to overweight (might be referred to as "a little
chubby"), not obese.

------
ashtonkem
Sufficient levels of Vitamin D are good for your health in general, separate
from this pandemic. Getting sufficient levels of it is something we all
should’ve been doing before anyways, which is not true of Chloroquine.

------
andreygrehov
I'm surprised the article barely mentions Vitamin K, which is needed along
with Vitamin D - D to mobilize the calcium and K2 to put it into the right
place.

[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5613455/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5613455/)

~~~
paulirwin
There is another important pair, too: Vitamin D and Magnesium. But consult
your doctor before taking extra amounts of anything.

There is a lot of misinformation on the web around Vitamin D, such as that
even high amounts (>= 5000IU) are tolerable and safe. After a blood test
showed me Vitamin D deficient, taking 5000IU (that size is readily available
over the counter at my grocery store) daily gave me disturbing heart
palpitations, which I didn't realize were related to Vitamin D until after
thousands of dollars in tests showed my heart to be perfectly healthy. It
wasn't until I had slacked off in taking the vitamins and then started taking
them again that I discovered the connection. Apparently magnesium has
something to do with it, but IANAD. (I was not taking magnesium supplements at
the time.) I can tolerate 1000IU occasionally, but people need to be aware
that not everyone tolerates supplements (especially high doses) the same.

I was happy to see the article you linked to above only claims Vitamin D is
considered safe up to 4000IU. Although IMHO, after my experience, anything
over 1000IU should require a prescription. Of course nothing would stop people
from taking five 1000IU OTC doses to get 5000IU, but I think most people know
better than to take five of the same type of vitamin daily without talking to
their doctor first.

~~~
illvm
These units seem _incredibly_ low to me. Your skin can generate almost 3000 IU
in just 15 minutes on the right day. Many doctors even recommend treatments of
150,000 IU or more, in one go to correct deficiencies (do not do attempt
without a doctor's recommendation and supervision).

I do not doubt your experience, but it seems incredible to me that just a 5000
IU supplement gave you heart palpitations. Then again, I've also read many
reports about incorrectly labeled products (e.g. milk, supplements, etc.)
which contained far more D2 or D3 than what was written on the tin, causing
toxicity.

~~~
paulirwin
I appreciate your respectful skepticism. It is entirely possible that the
supplements contained significantly more than on the label. However, I'd like
to point out that the generally recommended dose for supplements is only 800IU
in adults, with up to 4000IU only in the case of Vitamin D deficiency. The
"tolerable upper intake level" is 4000IU [1]. I am unable to track through
Wikipedia's sources here at the moment, but that aligns with the parent of my
original comment which I believe is in a peer reviewed journal. I would
imagine that number was determined due to people like myself not tolerating
amounts above 4000IU.

1:
[https://en.wikipedia.org/wiki/Vitamin_D#Dietary_intake](https://en.wikipedia.org/wiki/Vitamin_D#Dietary_intake)

~~~
mixmastamyk
The original RDA of 800 was designed to combat Rickets and has recently been
thought to be significantly too low for folks in higher latitudes. Given the
high number of variables perhaps simple RDA guidelines are not practical.

I take roughly 5k per day in the winter and it has helped a lot. See my other
post for details.

------
eli_gottlieb
Welp. I don't think it's gonna make _the_ difference if I get COVID-19, but I
did order some Vitamin D supplements. I live in a low-sunlight area, work
indoors, and don't drink a lot of milk. 75% of people in my region are Vitamin
D deficient. I can put two and two together.

~~~
chl
My guess: It might not make _the_ difference whether you _get_ it, but it's
not at all unlikely (given all the evidence that has accumulated so far &
extrapolation from experience w/ other viral respiratory infections) that it
will influence disease severity significantly.

------
psychometry
There are so many medical questions that can only be answered definitively
with large-scale, years-long randomized experiments. Anything relating to
supplements, where effect sizes are probably small, especially. These are
expensive and difficult to perform and there's (to my knowledge) no
institution dedicated to that goal.

------
antishatter
I feel like Vitamin D deficiency correlates with every disease. A large % of
everyone has a vitamin D deficiency so there is always a high correlation.

~~~
spuz
The percentage of the population that is vitamin D deficient can't affect its
correlation with disease. It's perfectly possible that after this, vitamin D
is added to tap water such that very few people are deficient but the
correlation with deficiency and disease would be unchanged.

~~~
nickles
> It's perfectly possible that after this, vitamin D is added to tap water

Vitamin D is fat soluble, not water soluble.

------
guptaneil
This requires a huge correlation != causation flag.

The article briefly mentions this, noting that it’s possible vitamin D is just
a sign of a healthy person, so of course they’ll do better with COVID. Another
correlation that doesn’t get discussed whenever vitamin D comes up is that
people with darker skin generally have less vitamin D, because our skin
doesn’t absorb sunlight as much. We also know that COVID is disproportionately
hitting colored neighborhoods in the US. Is that just because of vitamin D
differences? Who knows!

By the way, if you are a person of color, you probably need vitamin D
supplements. The recommended doses are for white people, so adjust
accordingly.

~~~
kedean
I felt like the article spent sufficient time on the idea that the explanation
could be that healthier people simply have higher vitamin D levels, and that
the vitamin D itself is not the cause. At no point did they choose a side on
that part, the bias was only that they believe vitamin D is a promising
avenue.

I really loved that the whole piece was informational, and not trying to
convince the reader that Vitamin D is or isn't a cure or remedy for anything.
It simply presented the available facts, the research, and the positives and
negatives of that research. It even explained multiple aspects and positions
of the debate on whether vitamin D supplementation is good or bad.

------
elric
With all this talk about Vitamin D and K deficiencies, which inevitable
meanders onto Magnesium and fish oil supplements and whatnot; maybe it's time
for a "vitamin subscription service"? Enter a bunch of information (location,
lifestyle, diet, health issues) and get tailor made supplements sent to your
home every month? The levels of some vitamins could vary depending on time of
year (more D in winter) or circumstances (more Mg when more active in summer).

Ideally all packaged into one tablet or something. I take an unholy cocktail
of supplements to help curb my migraines, that's 5 tablets/caps a day. Not
much fun.

~~~
Erwin
These guys create a supplement based off your DNA:
[https://www.nutrahacker.com/](https://www.nutrahacker.com/)
[https://ginihealth.com/](https://ginihealth.com/)

These let you create the vitamin/supplement mix you want:
[https://getvitaminlab.com/](https://getvitaminlab.com/)

last time I tried, it ended up quite more expensive than my D vitamins.

------
m0zg
FYI also, researchers are suggesting that the Lancet HCQ study everyone (and
the WHO) references nowadays is fake:
[https://www.theguardian.com/world/2020/may/29/covid-19-surgi...](https://www.theguardian.com/world/2020/may/29/covid-19-surgisphere-
hydroxychloroquine-study-lancet-coronavirus-who-questioned-by-researchers-
medical-professionals). The authors could not have had the data they claimed
they had. This is just one bit of news you will never find on CNN.

~~~
jakeogh
Yep. More:
[https://news.ycombinator.com/item?id=23305606](https://news.ycombinator.com/item?id=23305606)

------
haltingproblem
The article "Is Sunscreen the new margarine" argues that _" what made the
people with high vitamin D levels so healthy was not the vitamin itself. That
was just a marker. Their vitamin D levels were high because they were getting
plenty of exposure to the thing that was really responsible for their good
health—that big orange ball shining down from above."_ [1]. If this is true,
we have mistaken coincidence due to a common latent cause for causation.

The article "Limits of Vitamin D supplements" is a summary of the Lancet meta-
analysis: "Vitamin D status and ill health: a systematic review", which is
paywalled [2]. The review shows that Vitamin D supplementation has no
clinically beneficial outcome on heart disease, stroke, or cancer.

FWIW, I have been supplementing with Vitamin D for over a decade. I would
rather like Vitamin D to work because I have chronically low levels and it
would be good to have such a good silver bullet of a nutrient. I have not
stopped my supplementation but I do take more frequent walks in the Sun.

[1] [https://www.outsideonline.com/2380751/sunscreen-sun-
exposure...](https://www.outsideonline.com/2380751/sunscreen-sun-exposure-
skin-cancer-science)

[2] ([https://well.blogs.nytimes.com/2013/12/11/limits-of-
vitamin-...](https://well.blogs.nytimes.com/2013/12/11/limits-of-vitamin-d-
supplements/))

------
mixmastamyk
My anecdote. I learned about the importance of D3 on Steve Gibson's podcast
about a decade ago. At the time had a kid in preschool and spent almost the
whole year sick, so was quite intrigued.

Started with 1,000 IU a day and getting sick stopped abruptly. For the last
decade or so, haven't been sick more than one day, two at max, with one
exception.

Yes, believe I had CV in March and "walked it off" in about 6 days or so with
mild symptoms.

Last few years I've taken 5,000 IU several times a week (from Trader Joes,
which has an excellent price of $4.99). As compared to Albertsons which
disgustingly tries to get $15-20 for the same thing. Unfortunately this news
has made both C and D unavailable at Trader Joe's for months. We'll run out
soon and need to buy the gouging price somewhere else.

------
rafaelturk
For me this is a perfect example of wishful thinking.

It's really hard for average person to accept reality: This virus, like all
others, will last for a long time. We won't have, in a foreseeable future, a
treatment neither a cure. Cancer, HIV or even seasonal flue are good examples
examples of diseases that were discovered decades ago for which science still
don't have a cure, there are a few treatments or easing medication, but none
of them can be actually cured.

I expect that people will move from crazy solution to another on a regular
basis until a final cure is found.. my expectation is this will last for
years.

~~~
Dylan16807
We have extremely good treatments for HIV. And that one is particularly
difficult to cure because it infects your immune system.

Cancer isn't an infection and is a million different diseases lumped together.

We could prevent the flu much more reliably if it didn't mutate so much. Will
this disease do the same? Maybe. It's very hard to know.

~~~
nradov
So far SARS-CoV-2 mutates much slower than the various influenza strains due
to fundamental differences in the RNA transcription mechanism. That is
unlikely to change.

------
chl
dminder is a great app to estimate Vitamin D "intake"/production through sun
exposure (and also food, albeit this won't matter much for most people):

[http://dminder.ontometrics.com/](http://dminder.ontometrics.com/)

I only wish the algorithm used to derive the estimates was public/documented
somewhere ...

[http://dminder.ontometrics.com/Estimation.html](http://dminder.ontometrics.com/Estimation.html)

------
Havoc
I definitely dug out my vit D pills as a result of the coverage. Worst case
scenario it creates expensive pee. Maybe it'll have some upside though

~~~
makeset
> Worst case scenario it creates expensive pee.

Well, that's one thing you don't need to worry about. Vitamin D is fat-
soluble, so any excess isn't excreted in urine (hence the arguments over
effective vs. excessive dosage).

~~~
Havoc
>Well, that's one thing you don't need to worry about. Vitamin D is fat-
soluble

Good point. Thanks for pointing that out. I knew about the whole concept of
water vs fat but didn't occur to me in this context

------
ed25519FUUU
These studies need to keep up until we can fully account for the difference in
fatality not only worldwide, but state to state.

Why has Japan, with an older population (median age 47), a tiny island,
crowded indoor subways —- has only experienced 900 deaths and never locked
down! while some zip codes in New York experiences 2x that amount.

Even state to state the difference is alarming.

~~~
cgh
Diabetes is likely a factor:
[https://www.medscape.com/viewarticle/931132](https://www.medscape.com/viewarticle/931132)

And obesity is strongly correlated with diabetes:
[https://www.diabetes.co.uk/diabetes-and-
obesity.html](https://www.diabetes.co.uk/diabetes-and-obesity.html)

There is a distinction to be drawn between obesity rates in the US and Japan
and that might be part of the answer to your question.

~~~
nradov
New York state has about 6× the obesity rate of Japan.

------
api
One difficulty in determining if vitamin D actually helps with COVID is
determining if vitamin D levels are directly affecting outcomes or whether
they are a proxy for something else. For example: are low levels a proxy for
people who don't go outside much and therefore don't exercise?

That's a huge problem in medical studies generally.

~~~
pjkundert
There is strong evidence of this, summarized:
[https://www.outsideonline.com/2380751/sunscreen-sun-
exposure...](https://www.outsideonline.com/2380751/sunscreen-sun-exposure-
skin-cancer-science)

Huge inverse correlation between Vitamin D and all-cause mortality -- but
almost complete failure of vitamin D supplementation vs. cancer, heart disease
and stroke. What?

Turns out that sunlight produces vitamin D -- and a host of _other_ difficult
to detect artifacts, which seem to be at the root of the reduction in all-
cause mortality.

Seems interesting. Or, carry on -- I'm sure there's nothing to see here, and
your pasty-white overweight doctor's advice to avoid sun exposure is right...

~~~
Dylan16807
Doctors advising people to avoid sun exposure? Is that strawman based on
anything?

I hope you don't mean the advice to use sunscreen when you're going to be
outside so long you'd get sunburn without it.

~~~
jerf
How old are you?

I can assure you, whether it was the intent or not, that the message got out
in the 1980s and 1990s that all sunlight exposure is uniformly bad and its
only effect is to increase your likelihood of skin cancer, so everyone should
avoid it and unconditionally use strong sunscreen for any exposure.

------
raverbashing
Very good writeup

That being said, VitD has _much fewer_ potential side effects than CQ (in the
recommended dosage)

On this epidemic we should be looking at potential preventative quick gains,
especially as the most disrupting solutions are, well, disrupting.

------
szastupov
Covid or not, you should test for vitamin deficiency and supplement if
necessary. I do it every 3 month via Thriva (UK) and can see the progress.

------
forgot_user1234
How can you do science for long term effects?

where RCTs are not possible.

~~~
wenc
RCTs are not the only way to obtain evidence of causality.

In causal inference, limited causal claims can be made through observational
studies (where no control is done), such as retrospective natural experiments
[1]. These methods are of course limited by assumptions and by how closely
they match reality.

Note: while a controlled experiment is the gold standard, it is not always
feasible or necessary. We don't need to do RCTs on parachutes to prove their
efficacy for instance. [2]

\--

[1]
[https://en.wikipedia.org/wiki/Natural_experiment](https://en.wikipedia.org/wiki/Natural_experiment)

[2] [https://www.scientificamerican.com/article/volunteers-
jumped...](https://www.scientificamerican.com/article/volunteers-jumped-with-
or-without-a-parachute-to-gauge-its-effectiveness/)

------
kpfleger
Having read this whole piece, I think my review is much more comprehensive in
covering all relevant evidence:
[http://agingbiotech.info/vitamindcovid19/](http://agingbiotech.info/vitamindcovid19/)
Note that the title changed and many improvements made since it was first
posted to HN 3 weeks ago here:
[https://news.ycombinator.com/item?id=23119949](https://news.ycombinator.com/item?id=23119949)

In the title of this piece, analogizing to chloroquine is irresponsible. A
high % of readers will take the message to stay away from D and never read the
rest.

I'm glad he has a similar top-level rec as me: Take all measures to avoid
deficiency, probably by D3 of 2000-4000 IU/day (I'd prefer 4000). The piece
unfortunately fails to make the other most important top-level comment: that
all COVID-19 patients should have their D levels tested and more data on D &
COVID-19 severity should be published urgently (possibly based on records that
already exist). And all clinical trials for COVID-19 should be testing D
levels as well.

Overall, this piece is not emphatic enough that vitamin D may significantly
help during this COVID-19 crisis.

Several important responses to some of the top material in this piece:

The NYT article dismissing Holick is terrible and not worthy of being linked
at the top of this piece. I won't go into the point-by-point criticisms of
this article, but it's not worthy of a piece that is supposed to be weighing
evidence.

The bullet point claiming the COVID-19 association could still be a fluke does
not adequately acknowledge the causal aspects of the evidence: Many RCTs on D
supplementation helping viral/respiratory infections (Martineau et al BMJ
2017), D causally affecting rate of aging in roundworms, causal inference
model overwhelming supporting D's role as causal, studies on the correlation
correcting for age, sex, comorbidities, and reverse causality, and causal
mechanistic biological arguments. Some portion of the strength of the
correlation seen in the 1000+ patient cases published in preprint studies so
far may be due to other causal factors, but the causal evidence so far makes
it very unlikely for the full extent of the large effect size seen to all be a
fluke.

The piece wrote: "A healthy full body exposure to sunlight can generate 25000
IU of vitamin D in one sitting, without getting burned. 2000-4000 IU daily of
D3 supplements will also work." No. People wrongly believing that some sun
gives them enough is probably one of the causes of widespread deficiency. From
my review, in the "Practical considerations for avoiding D levels that are too
low" section: There are several studies showing that even a lot of sun
exposure leaves many people with insufficient D levels. For one list of
studies see Tsiaras & Weinstock, “Factors influencing vitamin D status” Acta
dermato-venereologica, 2011: “Studies in Hawaii (97), South Florida (98),
Southern Arizona (99), Brazil (100), rural India (101) and Queensland,
Australia (102) found that significant proportions of the study populations
had low vitamin D levels despite abundant sun exposure.” For example, in the
Hawaiian study, 51% of the 93 young, non-obese adults had D<30ng/ml despite
29hr/week (>4hr/day) in the sun at latitude 21 degrees. The variability in
both seasonal sun intensity and daily hours of exposure for any given
individual provide yet another reason that testing blood levels would be
helpful. These studies show that even those who seem to get a lot of sun
exposure should probably supplement if not testing to ensure adequacy.

Also, the bullet point summary in this piece fails to point out the history of
the RDA being set too low by statistical mistake. (Which I've updated my
review to include. The story is crazy---the original data used to set the RDA
would have resulting in 8000 IU/day if it had been analyzed correctly.)

