How does ATD work?

By ingesting a tryptophan-free drink containing large neutral amino
acids (LNAAs), tryptophan content in the blood is lowered because of an
induction of protein synthesis in the liver. Furthermore LNAAs compete with
endogenous TRP for transport across the blood-brain barrier, subsequently
lowering brain TRP levels. The rate controlling step in central nervous 5-HT
synthesis is the conversion of TRP into L-5-hydroxytryptophan (5-HTP) by
tryptophan hydroxylase 2 (TPH2) [Wurtmann et al 1980].
As TPH2 is not saturated at physiological concentrations of TRP, diminished substrate availability for TPH2 decreases brain 5-HT synthesis and release [Wurtmann et al 1980].

It has been shown that ATD Moja-De significantly lowers TRP in the blood and influx of TRP into the brain in humans [Dingerkuset al 2012] and lowers serotonin in different brain areas of mice [Biskup et al 2012].