Hi Radar,
I use Diet Whey Powder 3 times a week after my gym workout. Whilst as Peter says getting protein from food is important I find Whey Powder a cheap alternative to increase protein intake.
I did use to take Casein Protein overnight before my PCa. However, I stopped as a google search will show some concerns with Casein and PCa. I have also reduced my diary intake based on this.
Interesting that you lost weight on HT. I gained 4 KG in 3 months and am finding it tough to get back to my usual weight (lost 1 KG so far).
Richard