Amino acids are called building blocks of protein because your body uses them to manufacture proteins and other compounds that contain nitrogen. Some amino acids are called essential because you can't produce them but must obtain them from food. One of these, tryptophan, is especially rich in some common foods. Tryptophan is important for brain function and may help improve the quality of your sleep.
Poultry and Meat
Poultry is especially rich in tryptophan, with turkey providing 250 milligrams in a 3-ounce serving of roasted dark meat and about 280 milligrams in the same amount of roasted breast meat. Chicken offers about 250 milligrams in one skinless drumstick or 1/2 cup of diced, roasted breast meat. Beef, pork and lamb also contain lots of tryptophan, with the amount varying slightly with the cut. For example, a 3-ounce serving of lean meat from a rib-eye steak has about 300 milligrams of tryptophan, while 3 ounces of lean lamb has about 250 milligrams.
Seeds, Nuts and Beans
Some types of seeds, nuts and beans are also good sources of tryptophan. For example, 1 cup of raw soybeans contains about 100 milligrams, while 1 cup of kidney beans provides about 55 milligrams. Certain seeds also contain lots of tryptophan, as do some nuts. A 1-ounce serving of roasted sesame seeds provides about 100 milligrams, while 1 ounce of raw cashew nuts has about 80 milligrams, and the same amount of hazelnuts, or filberts, provides about 50 milligrams.
Milk and other dairy products contain moderately large amounts of tryptophan, with the content varying slightly depending on the type of food. For example, 1 cup of full-fat milk contains about 100 milligrams, while milk that's fortified with protein contains a bit more, about 130 milligrams per cup, depending on the exact product. Most types of cheese also contain tryptophan, with the amount depending on the type of cheese. Examples include ricotta cheese, which has about 150 milligrams per 1/2 cup, and Swiss cheese, with about 25 milligrams in 1/2 cup diced cheese.
Tryptophan is crucial for normal growth in infants and young children, and it also helps the body manufacture serotonin and melatonin, neurotransmitters that affect mood and sleep. In a clinical trial published in the April 2005 issue of "Nutritional Neuroscience," subjects who consumed extra tryptophan had improved sleep compared to those in a placebo group, leading the authors to suggest tryptophan might be a useful treatment for insomnia. Although no recommended daily amount of tryptophan has been identified, you can increase your intake of the amino acid by eating tryptophan-rich foods regularly. If you have questions about adding extra tryptophan to your diet, talk to your doctor or a registered dietitian.