There is a complex interplay in the body between various neurotransmitters and hormones which affect sleep.The key sleep hormone is called melatonin. It is released from the pineal gland during the late evening (stimulated by decreasing light levels); it peaks at around 3 or 4am, before dropping off sharply between around 6 and 8am, in part as a response to increasing light levels.

Melatonin is an almost identical molecule to serotonin (our key mood neurotransmitter), from which it is made, and both are made from 5-HTP, itself derived from the amino acid tryptophan which is present in most protein foods.

The conversion of amino acids into neurotransmitters and hormones requires nutrient co-factors, in particular the B vitamins, so a lack of these may also be responsible for low melatonin levels. The amino acid L-tryptophan is found in protein rich food, whereas 5-HTP can only be taken in supplement form.