A friend of mine was near death not so long ago, had every medical problem under the sun. Hormone imbalances, auto immune, digestive just everything was wrong, so much so that he was hold he didn't have long to live.
Then someone had the bright idea to check for malnutrition, and sure enough, he had a raging Vitamin D defeciency, along with various Bs.
They put him on 50,000 IUs ( International Units ) of D3, and all his medical problems disappeared.
Not enough sunlight had brought him to deaths door. Foods like samlon are dietry sources of D3.
There is apparently a point where no amount of sunlight will return you to normal levels of D3. Suppliments must be taken to restore a person back to normal in some serious cases.
It makes me wonder about so many pale sickly people stuffed in dark hospitals with no sunlight and no Vitamin D3.
D3 is anti cancer, but how many people fighting cancer are pale and confined in doors away from the Sun until they die.
I'm a gardener, and I know that living things need good light to grow well, and I have been convinced for along time that people need a good amount of sunlight as well.
When I worked nursing the aged and in palliative care I used to put people into the direct sunlight each day. I instinctively knew how important sunlight was, I could actually see the difference in people.
You just go with your gut feeling, and sure enough it turns out that sunlight is big medicine indeed.
So the moral of the story...

Get some freaken Sunlight.