I had an interesting experience recently. Because some of the best sources of manganese are grains and legumes, which we eliminate when eating paleo, I got the silly idea I should supplement manganese. A few days after starting the supplements I started having severe anxiety and sometimes full blown panic attacks. I am normally a pretty mellow person so this was very unusual for me. One day it was so bad I thought I was losing my mind and became severely depressed. I read up on manganese and realized the dose was too high. High doses can cause neurological problems. The term "neurological" normally applies to the physical side of the nervous system, such as coordination, memory issues, sense of touch, etc. But surely the the brain and behavior are part of the nervous system? I quit taking the manganese and after a few days felt much more myself. But it made me wonder if people who have anxiety, depression, or other mood or behavioral issues are people who eat large quantities of manganese-rich foods, e.g. grains. Not to pick on vegetarians but, as an example, I have known some who were awfully moody and edgy. Non-paleo vegetarians often eat a lot of legumes and grain combinations instead of meat to get their complete proteins, so they may be consuming more manganese than the average person. If I ate beans and rice every meal everyday could I go crazy?