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Comment by constantcrying | Hacker News Reader

TLDR: "Vitamin D supplementation might reduce the incidence of major cardiovascular events, although the absolute risk difference was small and the confidence interval was consistent with a null finding."

What I think would be interesting is looking at something like "time spent outside" to see whether Vitamin-D might be more significant on persons with too little sunlight exposure (physical activity would be an obvious confounder you have to control for).

Ultimately the study wasn't especially meaningful and weak effects aren't too surprising as a result.

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The best comment from a vitamin D study I remember is "you can lay buck naked on a rook in January all day but won't get enough vitamin D". Referring to northern US and Canada in winter.

It’s insanity to me that the only route people think you should get vitamin D is from the sun. In fact, most of us Caucasian Europeans should be getting it from our diet.

Cold water fish has the highest amount of vitamin D.

> It’s insanity to me that the only route people think you should get vitamin D is from the sun. In fact, most of us Caucasian Europeans should be getting it from our diet.

The fact that the skin of your ancestors rapidly evolved to become much lighter as they migrated to more polar latitudes tells you all you need to know about whether diet was an adequate source of vitamin D.

Light-skinned people are particularly well-suited to obtaining all the vitamin D they need from sunlight alone.

It is dark-skinned people currently living far from the equator who benefit the most from vitamin D supplementation, because the melanin in their skin reduces their ability to synthesize vitamin D from the meager amount of sunlight they get.

It wasn’t very rapid. In most of Europe white skin was introduced by famers migrating from the middle east who displaced the hunter gatherer populations at the beginning of the neolithic.

Thousands of years is the blink of an eye in evolutionary terms.

Maybe, but my point is that it initially appeared in the middle east (and probably in northern Eurasia at a similar time) but was likely first introduced throughout most of Europe by migrants/invaders from modern day Turkey.

The people who lived in Western Europe for likely longer that it took for white skin to evolve in the middle east/caucasus(?) region were much darker skinned.

Also given how long anatomically modern humans have existed several thousands years is not such a short period.

People get this idea that northern US must be at a high latitude just because it is cold in winter, and it simply isn't true. The 49th parallel roughly matches the latitude of Paris, London, Brussels, Munich, Prague or Vienna.

The problem isn't that you won't get enough sunlight if you lay down naked in the sun, the problem is that you can't because it is too cold.

None of those places are especially sunny in the winter though!

But Canada is! And that is what the comment I replied was talking about.

There is pretty much no place in Canada at all that doesn't have a total blackout of availability of Vitamin D from sunlight in the winter.

All the northernmost US states have a period of insufficient sunlight/angle to produce Vitamin D, and basically all of Canada is north of that.

Maybe there's an island that is Canadian territory that is south of say New York or San Francisco that I don't know about of course.

No the problem is the sun has to hit the earth's atmosphere at a certain angle in order for the correct wavelengths of light to pass through the earth's atmosphere. The amount of Vitamin D your body can generate from sunlight is based on your skin tone, where you are, the time of day, the day of the year, and the angle of the sun at that time and place.

Above/Below a certain latitude (N/S) there is a window of time where the sun never hits that angle at any point during the day, so you could sit outside naked all day long and still get zero vitamin D.

If this seems counterintuitive consider if you keep going far enough away from the equator and get into the arctic/antarctic the winter has no sunlight at all, and you clearly can't produce Vitamin D from sunlight if the sun never rises.

Yes that study (I can't recall the name of it) also noted the angle of the sun and limited daylight hours. Plus winter clothing means most often the only exposed skin is your face or even just half your face if you have a scarf on.

My city in Canada about 46.2 degrees north and about 300km from the eastern Maine border. Here in winter it gets light at 8am and dark at 4pm if there are no clouds. So most people are at work they go to work in the dark and leave when it is dark.

Why would that be interesting? Presuming the effect of limited sun exposure is posited as vitamin D deficiency, that is already an indication for supplementation, regardless of any effect on CVD risk reduction.

The purpose of a study like this would be to determine whether vitamin D supplementation is indicated for CVD prevention independent of vitamin D deficiency, which is why the study recruited from the general population, excluding only those in whom vitamin D supplementation would be contraindicated.

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