You've probably heard that it's the tryptophan in your Thanksgiving turkey that has you craving a nap after you eat. Turkey is a good source of tryptophan, and tryptophan does play a role in helping you sleep. But the connection between eating turkey and a good night's sleep isn't as straightforward as you might have heard.
What is tryptophan?
L-tryptophan is the official name of one of nine essential amino acids. They're essential because your body needs them to function but can't make them on its own. You must get them from your diet. Your body turns tryptophan into vitamin B3, also called niacin. Niacin helps your body create serotonin, which is a neurotransmitter. A neurotransmitter is a chemical substance in your body that carries a message. Serotonin is associated with your body's production of melatonin, which is a hormone that controls your sleeping and waking cycles.
Why doesn't eating turkey make you sleepy?
Eating turkey — or any other food high in tryptophan — doesn't make you sleepy because of the way tryptophan gets into your brain. In addition to tryptophan, turkey contains protein, which your body breaks down into other amino acids. The amount of tryptophan in turkey is small compared with the amount of other amino acids.
Tryptophan must use special transport proteins to get to your brain because of your blood-brain barrier (BBB). Your body is particular about what it lets into your brain and spinal cord, which make up your central nervous system. Your BBB is a line of cells that prevent viruses, fungi, bacteria, and parasites that might be in your blood from getting into your central nervous system. Since tryptophan can't freely circulate into your brain, it has to hitch a ride on a transport protein to cross the blood-brain barrier.
Other amino acids also use these transport proteins, so after you eat turkey, there are a lot of them competing to get to your brain. Because there isn't as much tryptophan as other amino acids, its chance of getting to your brain is pretty small. So after you eat a turkey, you may have more tryptophan in your body, but not much of it is getting to your brain, where it can help you produce melatonin.
Role of carbohydrates in using tryptophan
So how does your brain ever use tryptophan if it always has to compete with other amino acids? Carbohydrates play a key role in getting tryptophan into your brain. When you eat carbohydrates, your body releases insulin, which removes all amino acids except tryptophan from your blood. This gives the tryptophan that's stored in your body free access to the transport proteins and your brain.
The bottom line is that foods high in tryptophan provide your body with tryptophan, but they don't directly make you sleepy. Instead, when you eat foods high in carbohydrates, your body is able to use previously stored tryptophan. In the case of your Thanksgiving meal, it's the apple pie making you sleepy, not the turkey.
Foods high in tryptophan
Even though they won't make you sleepy right away, foods high in tryptophan provide your body with an essential amino acid. This ensures that you have it when you need it. Tryptophan doesn't just help you sleep better. The serotonin that tryptophan produces plays a role in stabilizing your mood and your feeling of wellbeing and happiness. It also helps reduce anxiety.
Foods that are high in tryptophan include:
- Red meat
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Other ways to boost your serotonin
If you're hoping for a better night's sleep, less anxiety, or a happiness boost from serotonin, here are some other ways you increase it naturally.
In addition to being good for your body, exercise is good for your mind. The muscle activation that happens when you exercise may allow more tryptophan to cross the blood-brain barrier. Exercising to fatigue may reduce the levels of other amino acids in your blood, which gives tryptophan greater access.
Although the evidence is indirect, exposure to bright light may help boost your serotonin level. In one study of healthy volunteers, there was a correlation between the level of serotonin and the number of hours of daylight, regardless of the season.
One study of people who practice meditation found that they have higher levels of serotonin than people who don't. They were also found to have higher levels of serotonin after meditating than before meditating.
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Ancient Science: "Meditation and Yoga can Modulate Brain Mechanisms that affect Behavior and Anxiety-A Modern Scientific Perspective."
Hormone Health Network: "Serotonin."
International Journal of Tryptophan Research: "L-Tryptophan: Basic Metabolic Functions, Behavioral Research and Therapeutic Indications."
Journal of Psychiatry and Neuroscience: "How to increase serotonin in the human brain without drugs."
MyFoodData.com: "Top 10 Foods Highest in Tryptophan."
?Nutrition and Health: "Recent research on the behavioral effects of tryptophan and carbohydrate."
Scientific American: "Does Turkey Make You Sleepy?"
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