soy protein (even soy milk) is better for women then men.
from reading, men can use it but in moderation. too much soy protein or soy milk will change our inhibitors for hormones, so say hello to mood swings and man boobs - only if you overdose on these items.
Personally, I don't like to take Soy Protein Isolate, I am not so sure that it is good for you (this is the same reason I generally make my own veggie burgers). I use Hemp protein. I like mine, it works good, although it does a bit of a strong taste - it is from Bob's Red Mill. I have also used Rice protein powder and that I can easily take, though I suppose it probably tastes a bit chalky. Anyway, that is just my take on the whole thing. (PS I have been doing a bit of the Thrive Diet and have felt great most of the time using Brendan's suggestions.)