In the USA we fortify milk with Vitamin-D too, but only a small amount - each 8oz cup (240ml) has 15% (3mcg) of your recommended daily allowance.

There's research that suggests that the RDA is way too low, plus many adults don't drink a lot of milk, certainly not enough to make significant impact on their vitamin-D intake.

https://www.cdc.gov/nutrition/infantandtoddlernutrition/food...

https://www.healthline.com/nutrition/fortified-milk#3

The last time I looked into this what I got was that there'd been a statistical error made in the process of determining the RDA, and it was just never corrected. The RDA is the amount that guarantees that only a certain fraction of the population has a deficiency, if everybody eats that much, but they calculated it so that only a certain fraction of population studies would find a deficiency on average. Furthermore, dietary vitamin D is absorbed rather poorly, so the amount of it you have to eat is immense compared to going out into the sun, resulting in really high "recommended" RDAs---it's the blood concentration divided by sensitivity but the measured sensitivity is surprisingly low. [1]

[1] A Statistical Error in the Estimation of the Recommended Dietary Allowance for Vitamin D, Paul J. Veugelers* and John Paul Ekwaru https://dx.doi.org/10.3390%2Fnu6104472

Also, isn't milk consumption unevenly distributed across the whole population? E.g. those with an Asian background I would expect to consume less milk than the population average.

True, I think food supplementation is hard to do in general since the dose needs to be appropriate for anyone that may consume it, with age ranging from infant to elderly.

>In Finland we put Vitamin D in milk that’s sold on normal shops.

I'd wager it's the same in all the Nordic countries, at least it's the same here in Sweden.

A couple a months ago when I spoke to my dad, he told me he had a checkup because he had been unusually tired, turned out that the only thing the testing showed was that he had d-vitamin deficiency.

What surprised me is that he was given prescription d-vitamins, since you can buy them anywhere without prescription.

You can get larger doses of vitamin D in one pill as a prescription. Like 20000 IU once every week or two instead of daily.

Also there is vitamin D2 and D3. The normal stuff you take is called D2. The D3 is made by the kidneys from converting D2. But those with certain diseases, the kidneys don't do the conversion so they provide vitamin D3 in the form called calcitriol. Its something I need to take due to my kidney failure.

At least in the UK, it's pretty easy to get D3 over the counter too. I've been buying D3 drops off of Amazon.

Looks like I misunderstood it. Calcitriol is different from D3. Normally your body converts D3 to calcitriol but those with certain diseases will not get it converted.

Calcitriol is actually the most confusing of my medications to manage since the dosage needs to be adjusted based on monthly blood tests. Things like amount of sun exposure can swing my numbers around. And it interacts with so many blood test numbers like PTH, phosphorus and calcium levels.

My wife was given these, during the early part of her pregnancy. I too, was surprised that they came via prescription.

The dosage did work out to be 50x what was in the standard products though.

UK government changed it's advice to recommend supplementation in the winter months (unsurprising given how far north the UK is).

You had a very limited coronavirus outbreak it seems. Does Norway have the same vitamin D supplementation policies? Their outbreak was similar in size to Finland’s.

https://en.wikipedia.org/wiki/COVID-19_pandemic_in_Finland

Edit: Interestingly, the source pdf notes the nordic countries have higher D3 levels than Mediterranean countries. And speculates this may help explain lower incidence up north.

————

The researchers around Petre Cristian Ilie have tested the number of Covid-19 deaths per 1 million inhabitants against the vitamin D level in 20 European countries and come to the following conclusion: The mean vitamin D level in the countries studied (mean 22.4 ng/ml, StDev ±4.24) correlates strictly with the number of Covid-19 infected per million population (mean 295.95, StDev ±298.73, p=0.004) and with mortality (mean 5.96, StDev 15.13, p<0.00001) The death rates in Spain and Italy are much higher than in Scandinavia. The researchers explain this with the statistically significant higher vitamin D level among the inhabitants of the Nordic countries: The study shows that in older people, the average blood vitamin D level in Spain is 10.4 ng/ml, in Italy, 11.2 ng/ml, while in the Scandinavian countries it is 18 ng/ml. The northerners obviously do have the better vitamin D levels, although the sun is not as intense there as in the south. This could either be because they are more active outdoors or because they get more vitamin D from food, e.g. fish, or both. Fat sea fish contains a lot of vitamin D. And southerners tend to spend their midday hours in the shade or indoors. Shadow, window glass and a longer way through the atmosphere (morning/evening, autumn/spring) reduce UVB radiation much more than UVA.

Norwegians worship the sun when it is present and they drink more milk as adults than in other non-Nordic countries. The milk is vitamin D supplemented. Sunbeds have become unpopular recently (3 years ago there were 3 tanning salons in walking distance of me now there are none).

The reasons that the outbreak has been minimal so far here are more complex though. Norwegians natually socially distance. The joke goes, "I am glad the lockdown is over and we can go back to the usual 5 meters - having to stand 1 meter from people was too close". Basically avoiding people for a few weeks was quite easy for many Norwegians. Younger ones tend to live in one bed flats rather than flat shares. Young people don't visit their parents and grandparents as much as they probably should. Also people buy into society and trust their government here. The PM announced a crisis and most people followed the guidelines for several weeks. Compliance dropped after a few weeks but it was clearly sufficient to break the infection chains.

What's the amount of Vitamin D supplementation? This is common in the States, but I wonder if Norway is higher.

> In Finland we put Vitamin D in milk that’s sold on normal shops.

Historically, the diet in that region included fish and other foods rich in vitamin D. I'm not sure what's the typical diet like these days.

But yeah, up north you definitely need to increase the intake of vitamin D. Same as Alaska in the US.