a nutritionist might confuse you even more. Every time I've seen a dietician (guessing its the same thing) they have been less clued up than me about the whole thing, and spent the whole time asking if he ate vegetable, and if i knew the effects of soy on infant rats? I found the whole dietician experience a waste of time, and wish I had followed my instincts.
With regards to the tolerance of soy. Even though we have done well, I think DS has a limit to the amount of soy he can tolerate, limited to about 200ml of soy milk a day or 2 yogurts.