These substances carry impulses between nerve cells. The substance that processes the neurotransmitter called serotonin is the amino acid tryptophan. B6 is essential for the conversion of tryptophan. Vitamin C increases uptake of tryptophan. Some food sources of tryptophan are soybeans, lentils, peas, brown rice, peanuts, pumpkins, sunflower and sesame seeds, kelp and algae.
Tyrosine is needed for brain function.
The consumption of protein-rich foods promotes the production of dopamine and norepinephrine, which promotes alertness. A lack of tyrosine can result in a deficiency of norepinephrine in certain sites of the brain, causing mood disorders, such as depression, stress and anxiety. Some food sources of tyrosine are soybeans, sunflower, almonds, peanuts, pumpkin and sesame seeds. An amino acid deficiency is frequently caused by protein malnutrition. Such deficiency states may be associated with improper diet, failure to digest and absorb properly, stress, infection or trauma, drug use, imbalances or deficiencies involving other nutrients and so forth.