Foods high in tryptophan include dairy products, chicken and turkey breast meat, eggs, mutton, venison, beef or calf's liver, salmon, and tuna, as well as halibut, shrimp, scallops, cod, mackerel and snapper. Vegetable sources include cruciferous vegetables such as broccoli and cabbage, soy milk, seeds, legumes and some fruits.
Tryptophan is an amino acid bound to the protein in food. It is an essential precursor to the formation of serotonin and niacin in the liver. Serotonin is an important neurotransmitter that helps regulate mood and sleep cycles, while niacin helps regulate blood circulation and cholesterol levels. A severe deficiency of tryptophan in the diet can lead to pellagra, a condition characterized by a pigmented rash, vomiting and diarrhea, fatigue, depression and apathy, headache, and memory loss. Milder levels of tryptophan deficiency can cause indigestion, vomiting, depression, difficulty concentrating, anxiety, irritability and fatigue.
Most people in developed countries get adequate tryptophan in their diets, but additional tryptophan may be helpful in managing insomnia and mood disorders such as depression, anxiety, seasonal affective disorder and premenstrual dysphoric disorder. There is also some evidence that consuming an extra 2 to 5 grams of tryptophan a day can increase the effectiveness of the antidepressant fluoxetine.