[disgruntledphd2]

Thanks for the links!

Interestingly, these papers together are much stronger evidence than either apart. This is because they use different methods. The OP is a population level study, while the second link you shared is a retrospective individual level study.

While I have some concerns with the stats in both papers (I'm always suspicious of p-values close to the magic number of 0.05), this does seem like interesting research, and potentially very helpful to dealing with Covid-19.

The irony of course, is that I suspect many of the Northern latitude people with high levels of Vit-D may be getting it through tourism to Southern Europe, which is very unlikely to happen this year.

[anpago]

If you live in a country with little daylight for part of the year your going to consider supplements of Vitamin d.

Also pickled herring is a delicacy in the many countries which have fared well in Europe in the fight against covid 19.

Also oily fish like salmon and mackerel are good for vitamin D.

Yet for many Brits it's a fish we rarely consider but is one of the biggest Concerns about the UK denying access to EU nation's to certain waters I believe with Brexit.

https://en.m.wikipedia.org/wiki/Herring_as_food

https://en.m.wikipedia.org/wiki/Pickled_herring

[nradov]

A brief vacation to southern Europe won't give a Scandanavian enough stored Vitamin D to last the rest of the year. Supplement use is common, and they tend to eat a lot of Vitamin D rich foods.

[distances]

Furthermore, vitamin D is added to some product types. At least in Finland there is a requirement for all fat free milk to contain additional vitamin D.