Nick,

Here is my understanding of the Amino acids contribution to the PD story:

I use a product called Dopavite which was designed specifically with the nutritional needs of PWPs in mind, providing the precursors necessary for natural dopamine production. Along with l-tyrosine it contains vit b6, folic acid, niacin, manganese, iron and zinc. Apparently you could be getting enough l-tyrosine, for eg., but if there is a prolonged deficiency of any of the additional building blocks/co-factors, dopamine production is compromised. Also, if you are taking the drug l-dopa, you need to separate its intake from dietary protein/amino acids regimes as there is competition for uptake. When complex interactions occur people always seem to blame the food or amino acids. If instead, you pitch the drugs, you have to wait a considerable length of time for the benefits of good diet/supplements to emerge.