From the first link, sounds like what the other reply said - vitamin D is important (but can be gotten from other sources), and I failed to mention it. Sorry. That said, it also recommends wearing a hat, and using sunscreen when outside for longer periods of time.
I unfortunately can’t read the second link without agreeing for them to sell my data, so that’s a nope.
What’s the point of capitalizing the first word of a sentence? Why are English letters pronounced differently in the same arrangements depending on the word? The language just is like that, it basically evolved over centuries to end up in this form.
Languages weren’t designed to work in a certain way, there wasn’t somebody smart saying they should work like X because Y, it’s just slow changes to how many people speak.