1
boing 1 point ago +1 / -0

Good points. If you have the option, definitely go for actual sunlight! In the north in winter it's hard though, and that's where supplementation can come in. Or cod liver.

2
boing 2 points ago +2 / -0

That may be mostly true, but supplementation can definitely help at least somewhat. Speaking from personal experience here. In my case it did a lot, but still only goes so far, and there seem to be other factors. I'm still trying to work it out.

3
boing 3 points ago +3 / -0

Check for a Vitamin D deficiency, that can have a lot to do with it. Magnesium can help, iodine can help. It can also be a digestive issue that prevents uptake of nutrients. Eating a crappy diet can also deplete nutrients. Ideally one of these things already leads to a lot of improvement, otherwise it is down to experimentation with other things, or fixing some other underlying issue. It's not easy, but it is worth every effort.