I was told that there are lots of latitudes in North America where the sun is at too low an angle for your skin to make vitamin D for large parts of the year so you should take it during those times and then you should be fine during the summer if you get outside enough.

I didn't see any mention of K2 (or missed it) - but a lot of D supplements combine with K2 as a "traffic cop" to keep calcium in bones and not arteries. I've not found a ton of evidence on this either, but seems to be a popular combination.

Just because vitamin D supplements helps with rickets doesn't mean supplementation helps all the other things we seem to attribute to vitamin D.

I think a good hypothesis for the discrepancy regarding why people with "naturally" high levels of vitamin D fare better than those who do not has to do with how vitamin D is produced naturally.

If you take the vitamin orally it might help for rickets and a few other issues but if you take it naturally via sunlight you might actually be having other benefits that aren't properly measured today.

With the current state of fear surrounding sunlight I doubt people are getting enough to see benefits and all studies use oral supplements instead of time in sunshine.

I started to take VitD on a whim and my mood and energy sure improved. Also I feel like I get sick less often. 3 friends whom I recommended VitD told me the same. Living in northern germany. YMMV.

I like this author but this post was only weakly intriguing.

More importantly, I'd like to know how long it takes to write a post like this.

Everything I write, I try to research and publish in under 2 weeks.

This post looks like it grew over time. I like that quality very much.

Leaving out skin colour from the conversations while mentioning 'randomized trials' and 'seasonal subpopulations' is problematic. Vitamin D production is highly tied to skin colour (melanin levels).

> Because physical exams are performed in mobile vans in NHANES, data could not be collected in northern latitudes during the winter

Why not?

I was taking 4000IU of Vitamin D daily along with 100 mcg Vitamin K-2 MK-7. My Vitamin D level was 60ng/ml. I've since dropped down to 3000IU per day. I go outside a lot but am either covered or using sunscreen since I sunburn easily.

Early into the Covid pandemic, there was talk that vitamin D had some protective effect. Did this ever pan out into any kind of recommendation supported by evidence ?

I think taking a supplement every day is a good idea. I used to suffer from low vitamin D levels constantly until I started taking a daily vitamin D tablet.