Tryptophan is an essential amino acid, thus must be part of our diet. It is needed to build serotonin, a neurotransmitter involved in the regulation of our mood, food behaviour and sleep. Tryptophan is a constituent of most protein-based foods (fish, poultry, red meat, eggs, cheese), but It is also plentiful in sesame and sunflower seeds, chocolate, oats, bananas, coconut and dried dates.