Tryptophan. Molecular model of the amino acid tryptophan. Its chemical formula is C11.H12.N2.O2. Atoms are represented as balls and are colour- coded: carbon (blue), hydrogen (gold), oxygen (red) and nitrogen (dark blue). Amino acids are the building blocks of proteins. Tryptophan is an essential amino acid. It cannot be synthesised by the body and so needs to be obtained from food. It is found in red meat, dairy products, chocolate, oats, bananas, mangoes, dates, eggs, seafood, fish, poultry, nuts, seeds, chickpeas and spirulina. Tryptophan is an important sleep aid, as it increases the levels of serotonin (a calming nerve chemical) and melatonin (a sleep-inducing hormone) in the brain. It also regulates appetite and mood.