[Throwawayaerlei]

> A friend of mine had cancer and they had him taking D3 immediately.

The last thing in the world a cancer patient needs is well nourished cancer cells, most grow and reproduce quickly.

[Zach_the_Lizard]

There is some evidence that vitamin D deficiency is associated with prostate cancer: https://clincancerres.aacrjournals.org/content/20/9/2289.abs...

There are a number of other studies on this. From what little I've read, if the effect is real,it seems the it is relatively weak, but still worth doing.