Amino acids that come from the protein you eat are the building blocks of your brain's network.

Most neurotransmitters are made from amino acids obtained from the protein in food you consume. Neurotransmitters are the brain
chemicals that motivate or sedate, focus or frustrate. Their complex interaction is what shifts your mood and changes your mind.
Neurotransmitters wag the tail of tadpoles and wage the tale of humanity.

http://www.fi.edu/learn/brain/proteins.html