Oh My God Vitamin D

How Art Thou Fallen from Heaven, O Lucifer, Son of the Morning!

There's them that say that anyone who takes vitamin D seriously is a lunatic of the most pitiable sort.

https://slatestarcodex.com/2014/01/25/beware-mass-produced-medical-recommendations/

“Scott,” he said “when somebody tells you they want to help you figure out the evidence base behind different supplements, ask them about Vitamin D. If they say it’s useful for anything besides bone health, run away.”

Vitamin D is not even a vitamin. All mammals can synthesise it, including us.

It's a hormone which is involved in calcium homeostasis.

But the synthesis needs sunlight.

Vitamin D deficiency causes rickets, a terrible bone disease

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

And that is pretty much all it causes, together with certain other allied conditions.

Rickets was once quite common in industrial cities in Europe where the smoke blocked out the sun. My mother, born in Sheffield-of-the-Black-Skies at the end of the second war, remembers people with rickets.

There's also evidence it was a problem in the Roman Empire. Particularly in Britain, which was not famed for its sunshine. (Caelum crebris imbribus ac nebulis foedum; asperitas frigorum abest. Must have been an unusually warm day.)

Apparently Roman-style city living meant people didn't get much sunlight.

These days we have a slightly different problem with vitamin D insufficiency. A combination of black-skinned people living in Europe, whose skin is well-defended against high levels of sunlight, and the fact that a lot of people are terrified of sunshine because it causes skin cancer, so they don't go out in the sun much, and when they do, they are covered in sun-proof chemicals.

Apparently the only reason we don't have epidemic rickets is because people are so bad at using sunscreen that they get a lot of UVB anyway....

But it wouldn't really matter.

These days if we see people with rickets, we give them vitamin D and calcium and the rickets goes away quickly. Which actually implies that the vitamin D supplements contain the right chemicals and actually work (at least it implies the the ones that doctors hand out do....). Bravo medical "science"!

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But hold one thought from the standard boring picture of vitamin D, the boring bone chemical.

In order to get enough sunlight to synthesise a crucial hormone that does a crucial thing, and without which you will die, you need to get enough sunlight to give yourself skin cancer, which will kill you. In the climate that your ancestors lived in for thousands of years.

I remember once I ventured unwisely to Antigua, and made a friend, a startlingly attractive woman whose skin was as black as the ace of spades.

One afternoon I saw her lathering herself in sunscreen. I did have a bottle of factor infinity, just in case I did ever have to go out in the full daylight, but I wasn't really bothering, partly because I don't get sunburn once I've tanned, but mostly because I had the sense to stay out of the appalling sun, and so wasn't suffering.

(It goes dark at 6 o'clock bang in Antigua every day. One has a few hours for lunch hiding under a parasol, invariably a full english breakfast and Susie's ferocious yet tasty chili sauce, ventures out to look for the Green Flash, and then the whole rest of the day is a delightful warm evening with strange stars. I saw the Plough set!)

I said to her: "I wouldn't have thought you needed that! You have a fine tan already."

And she said: "Are you kidding? If I go out in that all my skin will fall off!"

I remember being surprised by that. I wondered if perhaps Antigua is more sun-struck than whatever bit of Africa her people had been from, but never followed up on the thought.

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So why is vitamin D surrounded by woo?

Well the shocking thing about vitamin D is that it correlates with every illness under the sun.

During the great coronavirus panic, before the vaccines worked their slow and tortuous way out from under the blanket of health-and-safety where they had been imprisoned by paranoid lunatics who preferred saving face to saving lives, I actually took vitamin D supplements myself, without any great hope and with a real sense of shame, on the basis that the correlation between vitamin D levels and coronavirus deaths was so very, very, convincing.

And yet, every time someone actually tries vitamin D supplementation in a randomised controlled trial, for a thing with which it correlates really really well, the trial fails.¹

So I am thinking:

Correlation does not imply causation, as every schoolboy knows.

But causation definitely implies correlation. What would causation even mean, if it did not?

"Correlation implies Causation" is one of those funny things. A logical fallacy that is nevertheless a good heuristic.

Post hoc, propter hoc, as the Romans used to say, conscious even then of the double meaning.

And causality is a complicated thing.

In what way might causation relate vitamin D and every disease known to man, even though vitamin D supplementation never has any effect on any disease except rickets?

Easy, might say some hypothetical anti-seed-oil nutter, drowning so pitifully in confirmation bias that he would believe that the curse that on the dinosaurs so heavily fell might well have been a polyunsaturated curse.

The one effect that every man who has ever given up PUFAs has reported is increased tolerance to sun.

It really worries me that I have never noticed this. I've just never had much of a problem with sunburn. Even spending weeks on a beach in the south of France in the worst heatwave in living memory in my youth I never bothered with suncream.

But then I rarely leave grey Cambridgeshire these days, and if I do it's only to go to the grim Pennines, where there is even less sun and quite a lot more rain, and I spend an awful lot of time outdoors, and I tan well, so I tan gently as the winter ends, and usually by the time of full Summer I am already looking a bit subcontinental.

I feel these days that foreign countries are like the past. Full of lunatics and the food is terrible.

So maybe my childhood and adult immunity to sunburn has left me and come back and I just haven't noticed.

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But apart from me, everyone who has ever given up PUFAs has reported that they suddenly stop getting sunburn.

American correspondents report that, once upon a time, simply scurrying from their suburban mansions to their monstrous trucks to drive twenty yards to the newsagents on a Spring day was enough to make their skin fall off in sheets.

But those who have renounced the polyunsaturated evil report that they can now drive thousands of miles in open-topped pick-ups directly across the scorching deserts of Texas, stopping only to shoot anything that moves, all whilst actively enjoying the fierce rays of the formerly hated sun, and suffer no ill effects at all.

It is hard to imagine how such a thing could be, but perhaps making the membranes of skin cells from unstable easily oxidised unnatural frankenstein chemicals somehow renders them more easily damaged by high-energy ultraviolet radiation?

Who can say?

At any rate, suppose for a minute that PUFAs really do cause sun-intolerance.

Well, those labouring under such a burden might naturally spend less time in the sun. And as a result synthesize less vitamin D?

Not so little as to cause rickets. That is really hard, vitamin D is under homeostatic control like everything else, and American foods are generously supplemented with vitamin D anyway.

But enough that vitamin D levels correlate with PUFA levels, however imperfectly.

And suppose for a minute that PUFAs cause many terrible diseases.

Then it might be that vitamin D is (inversely) correlated with a number of bad things.

Whilst vitamin D supplementation makes no difference.

I could believe that.

That which correlates with vitamin D is caused by PUFAs.

And so my fall into madness is complete.

1. Strictly, sometimes the trials work, sometimes they don't, the effects are always very small, p~0.49, yadda yadda, it's all just noise and p-hacking....