This might be true - I cannot tell.

I just want to add that there are also voices which say that veganism might be bad for your long term health and I think this should be "brought on the table" as well. I think you always have to look at both sides of the coin. Please note that I do not know the "ultimate truth" regarding diet either, so no guarantees:

Also check out these two books:
Dr. Natasha Campbell-McBrides book:
https://www.amazon.com/Psychology-Syndrome-D-D-D-H-D-Schizophrenia/dp/0954852028/
She also gives youtube lectures.
Dr. Gundrys book:
https://www.amazon.com/Plant-Paradox-Dangers-Healthy-Disease/dp/006242713X/

So I would advice you to be very cautious - I suggest everyone simply tries which diet works best for him or her :-)