at the time those books were written, L-tryptophan was not available.
It has recently been cleared by the FDA and is now affordable.
I have a thread about it at the Vitamin forum on page 1.
Tyrosine is also found in dairy products.
__________________
All truths are easy to understand once they are discovered; the point is to discover them.-- Galileo Galilei
************************************
.
Weezie looking at petunias 8.25.2017
****************************
These forums are for mutual support and information sharing only. The forums are not a substitute for medical advice, diagnosis or treatment provided by a qualified health care provider. Always consult your doctor before trying anything you read here.