"Whatever the truth is, isn’t it about time we found out?"
Most other vegans I know seem to be very aware of the nutrition issues, and take EPA/DHA supplements and extra vitamins. "Nootch" - nutritional yeast - is also a very common ingredient used to boost vitamins and minerals.
It's of course hard to be 100% sure what's safe, but then eating meat also has it's risks - heart disease, cancer, e. coli. etc - as well as environmental costs.
Going vegan is quite a big step, and most people would benefit from eating a lot less meat.