The plates are cleared, the pie is half gone, and a warm heaviness settles over the living room. Somebody says what everybody is thinking: it is the turkey.
Probably not. A 3 oz (85 g) serving of roasted turkey holds about 0.26 g of tryptophan [1], the amino acid your body uses to make serotonin and melatonin. A can of sardines holds 0.25 g, and nobody blames sardines for a nap. Turkey is a good source of tryptophan in the way every protein food is, and no better.
The drowsiness has more likely suspects, and most of them are sitting on the same table: the size of the meal, the carbohydrates, the wine, a short night before, and a dip in alertness that arrives in mid-afternoon whether you ate or not. Here is the tryptophan story step by step, where it breaks, and what the studies say instead.
Does turkey have more tryptophan than other foods?
Tryptophan is an essential amino acid: your body cannot make it, so it has to come from protein. Turkey has plenty. The chart ranks foods by what one typical serving holds, using the values on our food pages [3] and the USDA entry for roasted turkey [1].
Drawn to scale. Serving sizes are the ones each food page uses, and chicken is raw weight. Turkey: USDA FoodData Central entry “Turkey, whole, meat only, cooked, roasted”, FDC ID 171481, 0.31 g per 100 g, so 0.26 g in 3 oz (85 g). The raw entry (FDC ID 171480) gives 0.27 g in 4 oz. Other foods: USDA FoodData Central via NutriScrolls.
Turkey lands in the upper middle. A 3 oz serving gives 0.26 g, a little more than a can of sardines and less than a 4 oz piece of raw chicken breast (0.32 g). A cup of soybeans beats them all at 0.42 g. The full ranking is on our tryptophan page.
Serving sizes differ, so a fairer test is how much tryptophan each food carries per gram of protein. If turkey were special, it would stand out here.
Drawn to scale. Our arithmetic: tryptophan divided by protein, both per 100 g, from USDA FoodData Central values (turkey: FDC ID 171481; other foods via NutriScrolls). Raw and roasted turkey give the same ratio, 10.7 mg per gram of protein.
It does not. Turkey carries 10.7 mg per gram of protein, against 12.6 mg for chicken breast, 13.3 mg for eggs and soybeans, and 17.6 mg for pumpkin seeds. If tryptophan alone made people sleepy, a chicken sandwich or a handful of pumpkin seeds would do it faster.
How does tryptophan get from your plate to your brain?
Eating tryptophan is only the first step. Your blood carries it to the blood-brain barrier, where it uses a carrier shared with other large neutral amino acids. What decides how much gets in is its share of that crowd, not its amount alone: raise tryptophan and more enters, raise its rivals and less does (Fernstrom, 2013).
Turkey brings its own crowd. Counting molecules from the USDA amino acid values [1], only about 3 of every 100 large neutral amino acids in roasted turkey are tryptophan. The other 97 compete for the same lane.
Our arithmetic from USDA FoodData Central entry FDC ID 171481: tryptophan, tyrosine, phenylalanine, leucine, isoleucine, valine and methionine, converted from grams to numbers of molecules. The grid shows the amino acids in the food protein, not in blood. The shared carrier is described in Fernstrom 2013.
So what does a meal do to the ratio in your blood? Earlier work had found that protein-rich meals lower the plasma tryptophan ratio and carbohydrate-rich meals raise it, at breakfast and at lunch (Lieberman et al., 1986). The studies below measured it directly. None of them used turkey.
Two ordinary breakfasts, one rich in carbohydrate and one in protein, changed the blood tryptophan ratio by a median of 54% between them
Nine overnight-fasted adults ate a carbohydrate-rich breakfast (69.9 g carbohydrate, 5.2 g protein) and a protein-rich one (15.4 g carbohydrate, 46.8 g protein), 3 to 7 days apart. Among the 8 who ate both, the difference ranged from 36% to 88%. Insulin rose only after the carbohydrate meal. Blood was sampled; brain tryptophan was not measured.
A drink with 40 g of the milk protein α-lactalbumin raised the blood tryptophan ratio by 50%, while gluten and zein lowered it
Six fasting men drank V8 juice containing 40 g of α-lactalbumin, gluten, zein or starch, with blood drawn every 30 minutes for 4 hours. The largest gap, between α-lactalbumin and zein, was about 3-fold. The ratio predicts brain uptake in rats; brain levels were not measured in these men.
In rats, eating carbohydrate raised tryptophan in the blood and then in the brain, followed by serotonin in the brain
A short report in Science. Insulin injections or carbohydrate in the diet produced sequential rises of tryptophan in plasma and brain, then of brain serotonin. It is an animal study, a starting point for the idea that meals can change brain chemistry.
Put together, these studies say that what you eat with protein, and which protein it is, shifts the ratio a lot. They do not say that a turkey dinner raises it. A protein-heavy meal would be expected to push the other way.
What does tryptophan turn into?
Even the tryptophan that gets in has other jobs. Most of it never becomes serotonin. About 95% of the tryptophan the body breaks down goes down the kynurenine route, which makes niacin (vitamin B3) among other products (Badawy, 2017). Only a minor fraction goes to serotonin, and brain serotonin production depends on tryptophan supply only in some nerve cells, in the hindbrain (Höglund et al., 2019).
Not to scale. The 95% figure is the share of the tryptophan that is broken down (Badawy 2017); serotonin as a small share (Höglund 2019); melatonin made from tryptophan with serotonin as an intermediate, in the pineal gland at night (Claustrat and Gronfier 2026).
Serotonin is then the raw material for melatonin, which the pineal gland releases at night, peaking around 3 a.m., depending on your chronotype. Melatonin is often called the sleep hormone, but one review says it is not that: it is a messenger of nighttime that sharpens the contrast between day and night (Claustrat and Gronfier, 2026).
Sleepiness is a tangle of clocks and signals. A single amino acid on a long pathway is a thin thread to hang a nap on.
Could a turkey dinner deliver a sleepy dose of tryptophan?
Sleep researchers have tested tryptophan itself, as a supplement. The amounts they used are the clue.
Tryptophan supplements of 1 g or more a day cut time awake after falling asleep to 28.9 minutes, against 56.6 minutes below 1 g
Systematic review and meta-analysis. The authors found 18 articles and could pool 4. The pooled effect on wake after sleep onset was a standardized mean difference of -1.08 (95% CI -1.89 to -0.28). Other sleep measures did not change, and with only four studies the result is fragile.
1 g of L-tryptophan at bedtime significantly shortened the time to fall asleep in people with mild insomnia
Laboratory study of 15 people who reported taking over 30 minutes to fall asleep. Doses of 0.25, 0.5 and 1 g were compared with placebo. Only 1 g reached significance; the lower doses showed a trend. The authors note that normal dietary intake is 0.5 to 2 g a day.
Drawn to scale. Turkey: FDC ID 171481, our arithmetic (0.31 g per 100 g). Daily need: 280 mg, WHO’s 4 mg per kg for a 70 kg adult, and average intake from US survey data, as reported on our tryptophan page [2]. Sleep trial: Hartmann and Spinweber, 1979.
Our 3 oz serving gives 0.26 g, and a big 6 oz helping 0.53 g. The average American already eats about 0.9 g a day [2], from everyday food, most of it on days with no turkey. The dose that helped in the trials was 1 g of purified L-tryptophan, taken at bedtime by people who had trouble falling asleep. A big helping of turkey gives about half of that dose, and the supplement evidence is itself modest.
If you are thinking of trying tryptophan for sleep, that is a conversation for your doctor. Our tryptophan page covers supplement doses and safety.
So what actually makes you sleepy after a big dinner?
Several suspects have been tested. Most of the studies below are small and each looked at a single meal or night, so treat each as a clue. Together they point away from the bird.
A big meal
Size matters. In one study, a high-fat, low-carbohydrate morning meal left 18 volunteers more fatigued three hours later than a low-fat, high-carbohydrate one, and the results fit with a role for the gut hormone cholecystokinin (Wells et al., 1997). A holiday plate is both large and rich.
After a 922-calorie lunch, sleep-deprived drivers showed more lane drifting and more sleepy brain activity than after a 305-calorie lunch
Double-blind crossover study in 12 young men who had slept 5 hours, driving a 2-hour monotonous afternoon drive in a simulator. The heavy lunch worsened lane incidents and EEG sleepiness; subjective sleepiness showed only a trend. The authors say the post-lunch dip is largely unrelated to lunch.
A carbohydrate-heavy plate
Stuffing, potatoes, rolls and pie bring a lot of carbohydrate, and carbohydrate has a more complicated record than turkey. It helped sleep onset at bedtime in one trial and made some people sleepier at midday in another.
Women, but not men, reported more sleepiness after a carbohydrate meal than after a protein meal
In 184 adults who ate a high-protein or a high-carbohydrate meal and were tested two hours later, men felt calmer after the carbohydrate meal. People aged 40 and over did worse on an attention test after a high-carbohydrate lunch, mostly from lapses of attention.
A high-glycemic rice meal four hours before bed cut the time to fall asleep to 9.0 minutes, against 17.5 minutes for a low-glycemic one
Twelve healthy men ate identical rice meals on separate nights: high-glycemic (jasmine) or low-glycemic (Mahatma). The high-glycemic meal given one hour before bed gave 14.6 minutes, slower than at four hours. No other sleep measure changed. This is about falling asleep at night, not about afternoon drowsiness.
A drink or two
Alcohol is a sedative, and it interacts with tiredness. Low and high doses can both help people fall asleep, and high doses disturb the second half of the night (Roehrs and Roth, 2001).
Alcohol at about half the UK legal driving limit worsened sleepiness-related lane drifting after a short night
Twelve healthy young men drove for two hours on an afternoon simulator, with alcohol or placebo, after normal sleep or restricted sleep. Alcohol and sleep restriction each worsened every measure, and together they worsened lane drifting more. The drivers did not feel sleepier than with sleep loss alone.
The clock, and the night before
Then there is the time of day. A dip in performance in the midafternoon is linked to a rise in sleep propensity and can occur even when the person has had no lunch (Monk, 2005). A big carbohydrate lunch makes it worse, according to the same review. And the Reyner study above shows how a short night amplifies the effect. Thanksgiving dinner often lands right in the dip, after an early start.
Evidence, not a score: each filled dot rests on a study named in this section (Reyner 2012, Spring 1982, Horne 2003, Monk 2005). The studies are small, of 12 to 184 people, and the turkey line records the absence of a trial.
How do you stay alert after the feast?
The studies suggest a few plain moves, none of which involves giving up turkey:
- Keep the plate moderate. In drivers who had slept 5 hours, the 922-calorie lunch made sleepy driving worse than the 305-calorie one.
- Go easy on the wine before a drive. Even low alcohol worsened sleepy driving after a short night.
- Sleep the night before. Sleep loss and alcohol each worsened sleepy driving, and together they worsened it more.
- Plan around the dip. Mid-afternoon drowsiness happens with or without lunch, so save the quiet part of the day for it.
- See a doctor if the sleepiness is constant. Strong drowsiness after most meals, or most of the day, is worth a medical check.
Turkey is a fine, ordinary protein food with a famous reputation. The nap is more likely to come from the size of the meal, the glass of wine and the clock.
Frequently asked questions
Does turkey have more tryptophan than chicken?
No. Roasted turkey holds 0.26 g of tryptophan in 3 oz (USDA FDC ID 171481), and raw chicken breast 0.32 g in 4 oz on our food page. Per gram of protein, turkey carries 10.7 mg and chicken breast 12.6 mg, so turkey is no richer in tryptophan than chicken.
Does tryptophan make you sleepy?
Supplements of 1 g or more a day shortened time awake after falling asleep in a meta-analysis of 4 studies, but other sleep measures did not change. A serving of turkey gives about 0.26 g. We found no trial that links a turkey dinner to sleepiness.
Why do I feel tired after Thanksgiving dinner?
The likely causes are a big, rich meal, a lot of carbohydrate, alcohol, a short night and the mid-afternoon dip in alertness. In a driving simulator study, a 922-calorie lunch worsened sleepiness signs compared with a 305-calorie one. The dip also occurs when no lunch is eaten.
Which foods have the most tryptophan?
By serving, soybeans lead on our tryptophan page: 0.42 g in a cup, ahead of chicken breast (0.32 g in 4 oz), sardines and mackerel. By weight, seeds lead: chia seeds hold 0.44 g per 100 g, and pumpkin seeds 0.33 g. See the full ranking.
Is it safe to take tryptophan to sleep better?
The evidence for supplements is modest: a meta-analysis of 4 studies found fewer awake minutes at night at 1 g or more a day. Whether a supplement suits you is a medical question, especially if you take other medicines. Ask your doctor first. Our tryptophan page covers supplement safety.
Sources
- U.S. Department of Agriculture, Agricultural Research Service. FoodData Central, SR Legacy entries: Turkey, whole, meat only, cooked, roasted (FDC ID 171481, fdc.nal.usda.gov/food-details/171481/nutrients); Turkey, whole, meat only, raw (FDC ID 171480). Accessed 24 Oct 2026.
- NutriScrolls. Tryptophan: needs (WHO, FAO and UNU, 2007: 4 mg per kg a day), average intake (Institute of Medicine, 2005), and foods high in tryptophan. nutriscrolls.com/proteins/amino-acids/tryptophan/. Accessed 24 Oct 2026.
- NutriScrolls. Food pages for soybeans, chicken breast, sardines, mackerel, tuna, pinto beans, eggs, pumpkin seeds and ground lamb (values from USDA FoodData Central as shown on each page). nutriscrolls.com/food/. Accessed 24 Oct 2026.
- Wurtman RJ, Wurtman JJ, Regan MM, McDermott JM, Tsay RH, Breu JJ. Effects of normal meals rich in carbohydrates or proteins on plasma tryptophan and tyrosine ratios. Am J Clin Nutr. 2003;77(1):128-132. doi:10.1093/ajcn/77.1.128
- Fernstrom JD, Langham KA, Marcelino LM, Irvine ZL, Fernstrom MH, Kaye WH. The ingestion of different dietary proteins by humans induces large changes in the plasma tryptophan ratio, a predictor of brain tryptophan uptake and serotonin synthesis. Clin Nutr. 2013;32(6):1073-1076. doi:10.1016/j.clnu.2012.11.027
- Fernstrom JD. Large neutral amino acids: dietary effects on brain neurochemistry and function. Amino Acids. 2013;45(3):419-430. doi:10.1007/s00726-012-1330-y
- Fernstrom JD, Wurtman RJ. Brain serotonin content: increase following ingestion of carbohydrate diet. Science. 1971;174(4013):1023-1025. doi:10.1126/science.174.4013.1023
- Lieberman HR, Caballero B, Finer N. The composition of lunch determines afternoon plasma tryptophan ratios in humans. J Neural Transm. 1986;65(3-4):211-217. doi:10.1007/BF01249083
- Badawy AA. Kynurenine pathway of tryptophan metabolism: regulatory and functional aspects. Int J Tryptophan Res. 2017;10:1178646917691938. doi:10.1177/1178646917691938
- Höglund E, Øverli Ø, Winberg S. Tryptophan metabolic pathways and brain serotonergic activity: a comparative review. Front Endocrinol (Lausanne). 2019;10:158. doi:10.3389/fendo.2019.00158
- Claustrat B, Gronfier C. Melatonin: some aspects of biochemistry, physiology, and pharmacology. Adv Tech Stand Neurosurg. 2026;54:49-78. doi:10.1007/978-3-032-18608-9_4
- Sutanto CN, Loh WW, Kim JE. The impact of tryptophan supplementation on sleep quality: a systematic review, meta-analysis, and meta-regression. Nutr Rev. 2022;80(2):306-316. doi:10.1093/nutrit/nuab027
- Hartmann E, Spinweber CL. Sleep induced by L-tryptophan. Effect of dosages within the normal dietary intake. J Nerv Ment Dis. 1979;167(8):497-499.
- Wells AS, Read NW, Uvnas-Moberg K, Alster P. Influences of fat and carbohydrate on postprandial sleepiness, mood, and hormones. Physiol Behav. 1997;61(5):679-686. doi:10.1016/s0031-9384(96)00519-7
- Reyner LA, Wells SJ, Mortlock V, Horne JA. ‘Post-lunch’ sleepiness during prolonged, monotonous driving – effects of meal size. Physiol Behav. 2012;105(4):1088-1091. doi:10.1016/j.physbeh.2011.11.025
- Spring B, Maller O, Wurtman J, Digman L, Cozolino L. Effects of protein and carbohydrate meals on mood and performance: interactions with sex and age. J Psychiatr Res. 1982-1983;17(2):155-167. doi:10.1016/0022-3956(82)90017-6
- Afaghi A, O’Connor H, Chow CM. High-glycemic-index carbohydrate meals shorten sleep onset. Am J Clin Nutr. 2007;85(2):426-430. doi:10.1093/ajcn/85.2.426
- Roehrs T, Roth T. Sleep, sleepiness, and alcohol use. Alcohol Res Health. 2001;25(2):101-109.
- Horne JA, Reyner LA, Barrett PR. Driving impairment due to sleepiness is exacerbated by low alcohol intake. Occup Environ Med. 2003;60(9):689-692. doi:10.1136/oem.60.9.689
- Monk TH. The post-lunch dip in performance. Clin Sports Med. 2005;24(2):e15-e23. doi:10.1016/j.csm.2004.12.002
Not medical advice
This article is general information, not a diagnosis or treatment. Talk to a doctor or registered dietitian before changing your diet, especially if you are pregnant, take medication or have a health condition. Read our medical disclaimer.
