You have probably heard about proteins if you’ve taken a biology class, or perhaps when talking about food or diet. Proteins are the building blocks that perform many vital functions in the human body, including providing structure, and regulation of cells and tissues. Proteins themselves are made of smaller molecules called amino acids. Before going too far into a biology lesson, I assure you the timing of this post is purposeful. Amino acids, or one in particular is related to a phenomenon experienced over the holidays, “Turkey Tired”. That amino acid is tryptophan.
Picture by freepik
Tryptophan (Trp) is an essential amino acid, meaning it must be obtained from our diet. Many will be consuming tryptophan in the form of turkey over the holidays. This amino acid may be best known for the old rumour claiming it is the ingredient that makes you so sleepy after a large holiday meal. Diet depletion of tryptophan has been associated with the inhibition of rapid eye movement latency and prolonged REM sleep. On the flip side, elevated tryptophan has been associated with an increase in subjective fatigue and enhanced quality of sleep (1).
You may wonder, how does tryptophan, consumed in our diet have an effect on our sleep? This relationship is facilitated by the gut-brain axis, a bi-directional communication axis between the nervous system and the gastrointestinal tract. Tryptophan, obtained from our diet is detected in our gut and the information is communicated with the brain via the gut-brain axis to determine the appropriate balance of the amino acid in the brain.
Now you may be wondering, why is tryptophan important to our brains? Tryptophan is the precursor to serotonin, a neurotransmitter that has a role in mood and cognition. Serotonin is also the precursor to melatonin, a hormone that is secreted by the pineal gland in the brain and is responsive to the light-dark cycle and regulates sleep and circadian rhythm. Therefore, upon entering the brain tryptophan is converted to produce serotonin and melatonin. Given their roles, clinical studies have shown that acute tryptophan supplementation improves attention scores, visual memory, and reaction times (1). This research has begun to demonstrate a persuasive argument for the role of tryptophan in the commonly experienced holiday phenomenon “Turkey Tired”.
However, we must consider how much tryptophan is actually found in the average serving of turkey. One pound of raw turkey contains 410mg of tryptophan (2), but individuals taking tryptophan supplements (L-tryptophan), to improve sleep or mood often take 4-5g per day (3). Therefore, one meal of turkey, gravy, and cranberries may not be sufficient to see a difference in your level of fatigue. It can, however, ensure a pretty amazing dinner with leftovers if planned accordingly.
References:
1. Jenkins TA, Nguyen JC, Polglaze KE, Bertrand PP. Influence of Tryptophan and Serotonin on Mood and Cognition with a Possible Role of the Gut-Brain Axis. J Nutrients. 2016 Jan 20;8(1):56.
2. Richard DM, Dawes MA, Mathias CW, Acheson A, Hill-Kapturczak N, Dougherty DM. L-Tryptophan: Basic Metabolic Functions, Behavioral Research and Therapeutic Indications. Int J Tryptophan Res. 2009 Mar 23;2:45-60.
3. Fernstrom JD. Effects and side effects associated with the non-nutritional use of tryptophan by humans. J Nutrients. 2012 Dec; 142(12):2236S-2244S