L-tryptophan is an essential amino acid. That means without a dietary source, humans die. Amazing then that its sale as a supplement was banned in the United Kingdom and the United States. It is present in most foods in the diet, yet its not allowed to be sold isolated in supplements. The reason for this was that a single batch of L-tryptophan caused a number of deaths because it was contaminated during manufacture. This is unfortunate because L-tryptophan is a very useful supplements to induce relaxation and sleep. This relates to the conversion of L-tryptophan to 5-hydroxytryptophan in the brain, a reaction catalysed by the enzyme tryptophan hydroxylase. Subsequently 5-hydroxytryptophan is decarboxylated to serotonin, a reaction characterised by L-aromatic acid decarboxylase. However, there is another way to get the benefits of L-tryptophan. Supplements of a 5-hydroxytryptophan are available, produced from the Griffonia simplicifolia seed. Once ingested 5-hydroxytryptophan enters the brain where it is converted to serotonin, thus having the same ultimate effect as L-tryptophan. Doses of around 50 to 100 mg are able to induce relaxation by increasing serotonin levels and induce sleep by the subsequent conversion of serotonin to melatonin.