Interestingly, on my meat only diet I get no fibre and very little vitamin C and I'm fine. Turns out meat is antiascorbic. I also think fibre has been way over-hyped.
I always like to see empirical evidence and it's been so long since I started to take the powder variety I'd forgotten where I learned about it. The following is just one reference. Definitely be careful, it can be like dynamite.