There's a research that winter sunlight in northern latitudes just does not convert precursors to vitamin D. Even when it's shining, no matter how long you are outside.

Well if you'd be so kind to move the earth so that we get enough sun during winter then that'll solve the problem.

What drove you to write this comment? There are enough countries where sun is an exception in winter and this is a valid problem.

Comment is neither helpful nor is it funny.

Interesting point, there is at least one theory out there which says that neither sunlight nor Vitamin D is necessary if an individual is really healthy. The ones that feel better on the Sun and/or Vitamin D are people who are at least mildly unhealthy and it's of form of addiction where the individual ought to keep taking something to just not feel miserable.

If this is true, then what would explain just oral vitamin D supplementation working?

that said, yeah let's all get outside more for sure

Sunlight alone don't help, it helps just because our body makes Vitamin D during the sunbathing process.

So sunbathing is one of many way of integrating Vitamin D in our body not THE way.

It's going to be sunny this morning, but also -14 and also I'm too far north for adequate Vitamin D synthesis in winter. But thanks for the advice.

It could be, but the same effect can be observed in people who dont change their outdoor habits but take vit D and omega 3 supplements

In most northern countries like the UK, there is simply not enough UVB in the winter to make any Vitamin D through sunlight.