Tryptophan is the chemical compound found in turkey that makes you crave that post-Thanksgiving-dinner-nap. Tryptophan isn't only in turkey, however--which is a good thing, because your body cannot synthesize tryptophan, yet it plays an important supporting nutritional role.
What Is Tryptophan?
Tryptophan is an amino acid, one of the building blocks for various proteins. It's classified as an essential amino acid, which means that your body cannot synthesize it so you must get it from the food you eat. In other words, it is essential that you eat a tryptophan-rich diet in order to maintain your body's health.
How Does It Work?
Tryptophan has two important functions in your body. The first is that it helps you synthesize niacin, an important B-complex vitamin. Niacin helps your digestive system to function correctly; it also assists in nerve function and in maintaining healthy skin. Tryptophan also helps synethesize serotonin, an important neurotransmitter that helps regulate moods and promote regular sleep. It's the latter function that may cause you to be sleepy after a heavy meal, Thanksgiving included.
Other Sources of Tryptophan
Contrary to popular belief, turkey does not contain higher levels of tryptophan than other poultry such as chicken. In fact, most protein-rich foods contain a good deal of tryptophan. These include milk, cheese, eggs, fish, soy products such as tofu, peanuts and peanut butter, tree nuts pumpkin seeds and sesame seeds.
Tryptophan Supplements
Over-the-counter tryptophan nutritional supplements are available through health food stores. They are sold primarily as a sleep aid and are used similarly to melatonin supplements in this regard. There is some indication that tryptophan supplements may also help with treatment of certain mood disorders related to low serotonin levels, such as depression, seasonal affective disorder and premenstrual syndrome. However, the scientific evidence for tryptophan's effectiveness in any of these roles is mixed. Always talk to your doctor before taking any kind of supplement.
Dangers of Tryptophan Supplements
In 1989, an outbreak of eosinophilia--myalgia syndrome was linked to a certain brand of l-tryptophan supplements. Eosinophilia myalgia, or EMS, is an illness that resembles the flu at first, but then goes on to cause severe muscle weakness as well as symptoms ranging from skin rashes to lung damage. EMS is incurable and occasionally fatal. The Food and Drug Administration banned l-tryptophan supplements in1991 but re-allowed them in 2001.
Other Causes of After-Meal Drowsiness
Although tryptophan's role in serotonin production is well established, it turns out that it might be only a minor player in what is scientifically referred to as "postprandial somnolence," or drowsiness after a meal. Rather, it's carbohydrates that likely to blame, assisted by any alcohol you consume. Also, after a heavy meal, blood rushes to the gut to aid with digestion, leaving less for other functions such as keeping you alert.
