| No: 17 | May 2008 |
| Does eating turkey make people sleepy?
It is a popular urban legend asserts that eating turkey makes you drowsy. Turkey, like many other protein foods, contains tryptophan, an essential amino acid that must be obtained in the diet. Tryptophan is a precursor of serotonin, a neurotransmitter that works to regulate sleep by inducing a calming sensation. However, tryptophan has to be taken on an empty stomach as a dietary supplement to cause significant drowsiness. When you eat turkey, the other amino acids present in the meat compete with tryptophan for absorption into the bloodstream. Even if there is a lot of tryptophan in the meal, only a small amount will ultimately reach the brain to be converted to serotonin. So it can't be the turkey alone that causes sleepiness. Rather, a combination of a high carbohydrate meal, fat, overeating, alcohol, and turkey leaves one feeling sleepy. It has been demonstrated in both animal models and in humans that ingestion of a meal rich in carbohydrates triggers release of insulin. Insulin in turn stimulates the uptake of large neutral branched-chain amino acids (LNAA) but not tryptophan (trp) into muscle, increasing the ratio of trp to LNAA in the blood stream. The resulting increased ratio of tryptophan to large neutral amino acids in the blood reduces competition with other amino acids for the large neutral amino acid transporter protein for uptake of tryptophan across the blood-brain barrier into the central nervous system (CNS). Once inside the CNS, tryptophan is converted into serotonin in the raphe nuclei by the normal enzymatic pathway. The resultant serotonin is further metabolised into melatonin by the pineal gland. Hence, these data suggest that "feast-induced drowsiness," and in particular, the common American post-Thanksgiving dinner drowsiness, may be the result of a heavy meal rich in carbohydrates which, via an indirect mechanism, increases the production of sleep-promoting serotonin and melatonin in the brain.Tryptophan cannot be manufactured in the body and must be obtained from the diet to maintain proper health. After tryptophan is ingested as protein, it is converted first to an intermediate, and then to serotonin via a series of chemical enzymes.
|
"Turkey meat contains a lot of an amino acid called L-tryptophan. When we eat foods that contain L-tryptophan, this amino acid travels in the blood from the digestive system and later enters the brain. The brain then changes the L-tryptophan into another chemical called serotonin. Serotonin calms us down and helps us sleep."
