In a Townsend Letter evidence-based article titled “Depression, Amino Acids, and Rubidium,” by Jonathan V. Wright, MD (Hon. ND), reports, “For over 40 years, my observation has been that low levels of essential amino acids are one major cause of depression. If essential amino acids are low, then neurotransmitters are very likely to be low also, and depression is a frequent result … Our nerve cells and other cells use specialized enzymes to transform the essential amino acid phenylalanine and its derivative tyrosine into noradrenalin, adrenalin, dopamine, and other naturally occurring stimulatory catecholamines. Without enough phenylalanine and/or tyrosine, our bodies can’t make nearly as much of these catecholamines, and many of us become depressed.”