In this podcast, the hosts dive into the myth of tryptophan from turkey causing the notorious Thanksgiving food coma. They explore the effect of tryptophan on sleepiness, its interaction with the blood brain barrier, and how Thanksgiving side dishes can impact its movement into the brain. They also discuss the theory that starchy Thanksgiving meals cause sleepiness by affecting amino acid levels and tryptophan conversion.
Tryptophan in turkey is not significantly higher than other meats, and consuming massive amounts is necessary to have sedative effects.
The interplay between various factors, such as the ratio of tryptophan to other amino acids and carbohydrate-heavy sides, determines the level of sleepiness after a Thanksgiving meal.
Deep dives
Tryptophan's association with sleepiness and Thanksgiving food coma
Tryptophan, an essential amino acid found in protein-rich foods like turkey, has been linked to sleepiness and the infamous Thanksgiving food coma. Although turkey contains tryptophan, it is not significantly higher in tryptophan compared to other meats or proteins. Furthermore, it would require consuming a massive amount of turkey to reach the dose of tryptophan that has been shown to have sedative effects. The idea that foods with tryptophan, like turkey and milk, cause drowsiness is based on the fact that tryptophan is a precursor to serotonin and melatonin, which are associated with sleep. However, tryptophan needs to cross the blood-brain barrier to affect sleepiness, and its transport is influenced by the ratio of tryptophan to other large neutral amino acids. Carbohydrate-rich sides, like mashed potatoes, can alter this ratio and potentially increase the levels of tryptophan that enter the brain. Overall, while tryptophan is present in turkey, it is not the sole contributor to post-Thanksgiving sleepiness.
Insufficient evidence and dosing concerns
When examining the evidence for tryptophan-induced sleepiness, it becomes evident that higher doses of tryptophan are necessary to produce significant effects. Studies have used doses much higher than what is typically consumed during a Thanksgiving meal. The exact minimum effective dose of tryptophan is still unknown. Additionally, the ratio of tryptophan to other large neutral amino acids plays a crucial role in whether tryptophan crosses the blood-brain barrier. Consuming only turkey may increase the plasma tryptophan level, but it does not change the ratio. On the other hand, carbohydrate-heavy sides like mashed potatoes can alter the ratio, potentially allowing more tryptophan to enter the brain. Therefore, it is not solely about the presence of tryptophan in turkey, but rather the interplay between various factors that determine the level of sleepiness experienced after a Thanksgiving meal.
Thanksgiving fatigue and the combination of factors
Regardless of the specific mechanisms behind post-Thanksgiving sleepiness, it is widely recognized that Thanksgiving is a tiring holiday. The exhaustion experienced after the meal may stem from a combination of factors, including the consumption of turkey, carbohydrate-rich sides, and potentially other variables like alcohol consumption. While the idea of turkey causing a food coma may be ingrained in popular culture, it is important to note that the dose and ratio of tryptophan, as well as the overall composition of the meal, contribute to the overall sleepiness experienced. Ultimately, Thanksgiving fatigue can be attributed to multiple factors, and it is a shared experience for many people.
Today we reach back into The Curious Clinicians archives, just in time for Thanksgiving. In this episode, originally posted in November 2021, Hannah, Avi, and Tony examine whether tryptophan from turkey actually causes the infamous Thanksgiving food coma. The answer might surprise you...
