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Does Tryptophan Make You Sleep?

21 November 2022

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After the platters are empty and the dishes are stacked high in the sink this Thanksgiving, take a look around the room at your annual family gathering. Chances are you’ll find family and friends scattered throughout the house relaxing in a food coma bliss. 

There is a longstanding myth that this fatigue, drowsiness and overall lethargy can only be the culprit of one thing – the turkey. For years, tryptophan, an amino acid in turkey, garnered headlines in the media for making you sleepy. However, there is another more plausible explanation that helps give context to this common occurrence around the holidays. 

What is tryptophan?

Amino acids are molecules that join together to form proteins. Most of the foods we eat contain a combination of different amino acids. In total, 20 amino acids exist in foods – nine essential and 11 non-essential. 

L-Tryptophan, referred to more commonly as just tryptophan, is an essential amino acid, meaning your body doesn’t produce it. Most sources of tryptophan come from plants or animals. 

Whenever your body digests tryptophan, it travels through the blood to the brain where it’s used to synthesize the neurotransmitter serotonin. This chemical messenger serves many roles, including regulating your mood, sleep, digestion and sexual arousal. It’s also considered one of the happy chemicals in your brain. At night, the brain converts serotonin into melatonin, a hormone that helps regulate your circadian rhythm to help you sleep 

The digestion process also converts tryptophan to niacin, a B vitamin that plays an important role in converting food into energy. 

Tryptophan in turkey

Most turkey consumed on Thanksgiving comes in the form of white meat (turkey breast) or dark meat (turkey legs, wings or thighs). A 1-cup (100 grams) serving of roasted turkey breast contains 318 mg of tryptophan, while roasted dark meat has 275 mg. 

Tryptophan is one of the many amino acids in poultry. Histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine are also present. 

Here is a closer look at the makeup of amino acids in a serving of roasted turkey breast. 

  • Lysine: 2.63 g 
  • Leucine: 2.24 g 
  • Arginine: 2.02 g 
  • Alanine: 1.82 g 
  • Valine: 1.5 g 
  • Isoleucine: 1.45 g 
  • Threonine: 1.26 g 
  • Phenylalanine: 1.13 g 
  • Tyrosine: 1.1 g 
  • Histidine: 0.868 g 
  • Methionine: 0.811 g 
  • Tryptophan: 0.318 
  • Cystine: 0.313 g 

As you can see, tryptophan is one of the scarcest amino acids found in turkey – there are other amino acids in turkey competing with tryptophan once it enters the body. In other words, it’s unlikely to be enough tryptophan to increase serotonin levels to make you sleepy. 

Foods highest in tryptophan

Chicken, pork and ham, not turkey, all have higher amounts of tryptophan per serving. Other foods, such as sunflower seeds and soybeans, are also high in tryptophan but people don’t typically eat a large quantity in one sitting. Edamame is one of the few exceptions – a cup contains 195 mg. 

The following is a list of foods highest in tryptophan, according to data from the U.S. Department of Agriculture.  

  • 1 cup chicken breast, roasted: 507 mg 
  • 1 cup of diced ham, roasted: 505 mg 
  • 1 skin-on chicken thigh: 359 mg 
  • 1 cup sockeye salmon: 335 mg 
  • 1 center loin pork chop, broiled (170 g serving): 420 mg 
  • 1 cup duck breast, roasted : 337 mg 
  • 1 cup turkey breast, roasted: 318 mg 
  • 1 cup ground turkey: 312 mg 
  • 1 cup skirt steak, broiled: 288 mg 
  • 1 cup lamb shoulder, braised : 286 mg 
  • 1 cup dark turkey meat, roasted: 275 mg 
  • 1 cup pork tenderloin, roasted: 274 mg 
  • 1 skin-on chicken drumstick: 246 mg 

Other than meat and seafood, dairy, grains and nuts also contain moderate levels of tryptophan. Examples include a cup of oatmeal (147 mg), a 1-ounce serving of mozzarella cheese (146 mg), a cup of black beans (105 mg), a cup of whole milk (98 mg) and an ounce of cashews (81 mg). Additionally, a slice of bacon has 47 mg of tryptophan, which can add up considering most people eat two to three slices of bacon in a sitting. 

Why does Thanksgiving dinner make you sleepy?

Postprandial somnolence is the medical term for fatigue or sleepiness after eating a meal. Sometimes, you’ll hear this referred to as a food coma. There are several factors that can contribute to fatigue after eating a meal, especially a heavy one. 

Do carbs make you tired?

There’s a reason why a perceived association exists between Thanksgiving dinner and fatigue.  For starters, as much focus as turkey receives, many of the fats and calories consumed come from carb-laden meals – think rolls, pies, mashed potatoes, casseroles, stuffing or dressing. 

Eating meals rich in refined carbohydrates causes a spike in insulin, a hormone produced by the pancreas to regulate glucose (blood sugar) levels. White potatoes, white bread and foods with added sugars are all high-glycemic foods, meaning your body digests them faster and causes a quick spike in your blood sugar. In turn, the pancreas makes insulin to lower glucose levels.

This process of quickly spiking and then lowering blood sugar levels is a vicious cycle and can cause hypoglycemia. Symptoms of hypoglycemia include fatigue, headaches and hunger. A sugar rush is a classic example of this phenomenon. 

Compounding the issue, insulin can make it easier for tryptophan to travel to your brain by reducing the amount of other amino acids in the blood. In other words, insulin frees up a path for tryptophan to boost serotonin levels. However, this process only leads to a slight increase in tryptophan. 

In either case, the protein from turkey and the carbs that cause insulin spikes serve as a double whammy of sorts since both impact serotonin production. 

The digestive system working overtime

Some Thanksgiving dinners – from the rolls at the start of the meal to the desserts at the end of the meal – can contain as many 3,000 to 4,000 calories.  

Consuming that much food in a short amount of time is no easy task for your body to handle. In general, heavy meals – especially those high in fat and loaded with sugar or other refined foods – take a toll on your body since it takes more energy to digest. 

A typical meal can take more than a day to fully digest. Imagine eating a full meal the day before, then loading up your stomach with apple pie, pumpkin pie, green bean casserole and mash potatoes? That’s where the fatigue comes in. 

How to avoid Thanksgiving drowsiness

Limiting foods high on the glycemic index is one of the easiest ways to avoid feeling sluggish and fatigued after your meal. 

High-fat foods also take longer to digest, which can lead to fatigue. While it’s important to treat yourself and indulge in a few of your favorite items, be mindful of balancing your plate. Opt for a salad or vegetables to help offset the macaroni and cheese and other fattening side dishes. 

Once you eat, consider going for a walk around the neighborhood. This is an ideal excuse to walk your dog or spend time outdoors with your family and friends. A brisk walk will help move food in your stomach to the small intestines to speed up digestion. 

Visit the INTEGRIS Health For You blog for more lifestyle, wellness and food content. 

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