Is turkey the only meat that makes you sleepy?

Turkey has no known special effect, and it is not even the richest food in tryptophan. USDA's two records for roasted turkey breast give 0.287 and 0.364 grams of tryptophan per 100 grams, against 0.362 grams for roasted chicken breast and 0.482 grams for hard parmesan. In a 1998 sleep-lab study, people grew sleepier after both high-fat and high-carbohydrate meals, so the effect does not depend on turkey.

How much turkey do you have to eat to make you sleepy?

Eating more turkey should not push more tryptophan into the brain, because every extra slice also adds the amino acids that compete with it at the blood-brain barrier; in rats, protein diets raised blood tryptophan without changing brain tryptophan. In USDA's figures for roasted turkey breast, five of those competitors outweigh tryptophan about 18 to 1. A bigger meal can still add to sleepiness: in a 2012 simulator study of young men who had slept five hours, a 922-calorie lunch caused more sleepiness-related lane drifting than a 305-calorie one.

Is tryptophan in turkey a myth?

The tryptophan is real; the claim that it makes turkey sleep-inducing is the myth. Turkey has about as much tryptophan as chicken, and in Fernstrom and Wurtman's 1972 rat experiments, protein-containing diets raised blood tryptophan without changing tryptophan or serotonin in the brain.

What does turkey do to your brain?

Turkey's amino acids reach the brain the same way any protein food's do. The brain makes serotonin from tryptophan, but turkey's tryptophan arrives with larger amounts of five competing amino acids (tyrosine, phenylalanine, leucine, isoleucine and valine), so the brain's share should not rise the way it can after a carbohydrate-rich meal with almost no protein.

Why do you get sleepy after a big meal?

Eating can raise sleepiness: in a 1998 study of 16 men and women, sleepiness was significantly greater 1.5 hours after a meal than before it, whether the meal was high in fat or high in carbohydrate. A mid-afternoon dip in the body clock may add to it and can happen even with no lunch at all, and alcohol makes people fall asleep faster, more so when they are already sleepy.

Why Does Turkey Make You Sleepy? Its Tryptophan Is Ordinary

If tryptophan were the reason turkey makes people sleepy, chicken would do the job just as well. In the US Department of Agriculture’s food composition tables, roasted turkey breast carries 0.287 or 0.364 grams of the amino acid per 100 grams, depending on the sample set, and roasted chicken breast 0.362 grams. Hard parmesan beats both birds at 0.482 grams.

Why does turkey make you sleepy?

A meal, the mid-afternoon body-clock dip and alcohol can all make you sleepy, and turkey is not special. In a 1998 study, people were measurably sleepier 1.5 hours after eating than before, whether the meal was rich in fat or carbohydrate. Turkey has about as much tryptophan as chicken breast, and in rats, protein diets that raised blood tryptophan left brain tryptophan unchanged.

Chicken and turkey finish in a near tie

Food, per 100 grams	Tryptophan
Parmesan, hard	0.482 g
Turkey breast, meat only, roasted (retail parts)	0.364 g
Chicken breast, meat only, roasted	0.362 g
Turkey drumstick, meat only, roasted (whole bird)	0.321 g
Chicken dark meat, meat only, roasted	0.320 g
Turkey dark meat, roasted (whole bird)	0.295 g
Turkey breast, meat only, roasted (whole bird)	0.287 g
Chicken drumstick, meat only, roasted	0.273 g

Cut for cut, the lead changes hands: chicken wins on whole-bird breast and dark meat, turkey on drumstick and thigh, and USDA’s retail-parts turkey breast edges chicken breast by 0.002 grams. The poultry rows span less than a tenth of a gram. Even a tie is more than the chicken managed in the argument over which came first.

The tryptophan myth breaks at the blood-brain barrier

The myth rests on real chemistry, since the brain builds the neurotransmitter serotonin from tryptophan; its weak link is getting more tryptophan into the brain. In 1972, John Fernstrom and Richard Wurtman reported in Science that when rats were given injections of tryptophan or insulin, or fed carbohydrate, tryptophan rose in their blood and in their brains. Diets containing protein pushed blood tryptophan up even further, and brain tryptophan did not change.

What seemed to decide the brain’s share, they wrote, was not blood tryptophan alone but its ratio to five other amino acids (tyrosine, phenylalanine, leucine, isoleucine and valine) “that compete with it for uptake into the brain.” Turkey delivers all six together. In both of USDA’s roasted turkey breast records, the five competitors outweigh the tryptophan roughly 18 to 1.

In Fernstrom and Wurtman’s rats, protein diets put more tryptophan into the blood than carbohydrate did, yet the carbohydrate raised brain tryptophan and the protein did not. Roasted turkey breast carries about 18 grams of competing amino acids for every gram of tryptophan.

In people, a 2003 MIT study in the American Journal of Clinical Nutrition found that the blood tryptophan ratio differed by a median 54 percent between a carbohydrate-rich and a protein-rich breakfast, and noted that high-protein diets were already known to depress it.

In rats, a little protein cancels the carbohydrate effect

A common correction moves the blame one dish along. Wikipedia’s tryptophan article says the drowsiness “may be caused by other foods eaten with the turkey, particularly carbohydrates”: insulin from the carbohydrate pushes competing amino acids into muscle, and tryptophan gets a clearer run at the brain.

In a 1986 study in Metabolism, Yokogoshi and Wurtman gave fasted rats meals of 70 to 75 percent carbohydrate, which raised the blood tryptophan ratio. Adding as little as 5 percent casein fully blocked the rise, probably, they wrote, because the protein added far more competing amino acids than tryptophan to the blood. At 10 percent protein, casein, peanut meal and gelatin fully blocked it, egg white only partly, and lactalbumin not at all.

The carbohydrate-rich breakfast in the 2003 study held 5.2 grams of protein; 100 grams of roasted turkey breast holds about 30 grams. “The carbs did it” was shown on meals that were mostly carbohydrate, and as an account of a turkey dinner it is overstated. Single causes fare no better with cilantro: the 23andMe team that linked soap-tasting to a variant near OR6A2, often called the cilantro soap gene, found it explains only about 0.5% of the variance in who finds cilantro soapy.

A meal can make people measurably sleepier

In a 1998 University of Sheffield study in the Journal of Applied Physiology, 16 men and women ate a high-fat and a high-carbohydrate meal of equal energy, four hours apart. On the Multiple Sleep Latency Test, which times how quickly a person falls asleep, sleepiness was significantly greater 1.5 hours after the meals than before, with “no differences in sleepiness according to the composition of the meal.” The authors, who staggered meal times by two hours between groups, suggested the rise was “not solely due to circadian rhythms.”

Size can add to it. At Loughborough University, 12 young men limited to five hours’ sleep the night before ate a 305-calorie lunch and, on another occasion, a 922-calorie one, each followed by two hours in a car simulator (Physiology and Behavior, 2012). After the heavy lunch they drifted out of lane more often and their EEGs showed more sleepiness, though only after the first 30 minutes.

Neither study measured blood flow, so they offer no support to the popular explanation that a heavy meal brings on drowsiness by shifting blood to the digestive system.

The afternoon dip can arrive without lunch

In a 2005 review in Clinics in Sports Medicine, Timothy Monk of the University of Pittsburgh Medical Center describes a mid-afternoon dip in performance, seen on some tasks and in some people, that comes with a rise in sleepiness. He calls it “a real phenomenon that can occur even when the individual has had no lunch and is unaware of the time of day.” He adds that a high-carbohydrate lunch makes it worse, a point the Sheffield comparison did not bear out.

The Loughborough paper calls the dip “largely unrelated to lunch.” It comes from the body’s internal clock, the same kind of timer that sets a rooster crowing before dawn. A feast served in mid-afternoon lands on top of it.

Alcohol hits harder at a sleepy hour. Reviewing the research in 2001 for the National Institute on Alcohol Abuse and Alcoholism’s journal, Timothy Roehrs and Thomas Roth of Henry Ford Hospital report that alcohol made people fall asleep faster on the Multiple Sleep Latency Test, more so at higher doses. They add that “increased sleepiness compounded alcohol’s effects,” even in the same person tested at different times of day.

The myth was a sitcom plot by 1997

On 6 November 1997, the Seinfeld episode “The Merv Griffin Show” sent Jerry and George after a girlfriend’s vintage toys, which she would not let Jerry touch. In Wikipedia’s episode summary, the plan for putting her to sleep is a dinner of turkey, which “contains tryptophan,” and red wine, followed by a four-hour home movie. Even the sitcom did not trust the bird to work alone.

Put a roast chicken on the Thanksgiving table instead, serve it at the same hour, and nothing in these studies predicts livelier guests. The turkey has been taking the blame for the meal and the hour. Strictly FYI.