The shirt will cost you $18 and will allow you to advertise your love for one of the key monoamine neurotransmitters in the brain.
Tryptophan is an essential amino acid that is synthesised into serotonin. It is found in many fruits, nuts and vegetables. Walnuts are a particularly good source.
It’s not clear how many walnuts were eaten to produce this t-shirt, but the results are fantastic anyway.