That's true, the sodium is very, very horrible in the boullion along with the chicken (meat) fat and all the other impossible to pronounce ingredients... As such, all commercially processed boullion should be avoided when on a juice fast.
Of course, it's a personal decision, but at least now, it's an informed personal decision.
When I made veggie broth on my fast, I used more veggies than the water they simmered in and all kinds of herbs and spices and garlic and ginger, etc and the broth turned out to be quite rich and tasty without the use of any kind of boullion.
Somewhere on my blog (prolly on the first page at the beginning) it discusses how to make tasty veggie (and fabulous fruit) broth.