BIWI, sorry to hear that. ((()))
I'm a bit obsessed with Vit D and make sure my kids have some everyday. I didn't know about the link with cancer.
About 2 years ago, I was being seen by a consultant about thyroid issues. The medication was at the right level but I felt like poo. Lots of aches and pains and joint stiffness. He tested my Vit D levels and they were about 14 or 16. The gp said that was a lot lower than he'd seen so gave me a Vit d injection. The next day I felt like a completely different person. I was also given tablets of 2000iu per day and after 6 months things were SO much better.
I was told by the consultant to take it forever. The gp said nonsense, so I stopped. Gradually I started to feel rubbish again. So now, if I remember, I take some everyday. It's important to lots of cell activity and bodily functions as well as helping with the absorption of calcium.
Anyway, withering on, but with the almost complete lack of sun in the uk last year, I would bet money on the fact that a large percentage of the population are deficient in Vit D.
Incidentally, if you do take this, then try and get D3' cholecalciferol, as It's better that the D2 ergocalciferol, as it's more easily absorbed ino the body.
Also, I've read that Vit C can really help with symptoms of depression.
Sorry for the off topic essay!