Getting enough sleep every night is kind of a big deal.

Lack of sleep is shown to cause numerous health conditions, including heart disease, cognitive impairments, and low testosterone in men. (2)

In fact, just one week of sleep restriction leads to plummeting T levels in young males. (1)

In order to improve their sleep duration, as well as quality, people look for various solutions. Some opt for medications, while others choose natural supplements, such as l-tryptophan.

We won’t talk about medications here since they’ve been shown to actually sedate you, instead of making you fall asleep. And there’s a big difference between the two. Studies show that sedation kills deep (REM) sleep. (3)

Instead, we’ve chosen a natural, and more effective route, which is consuming l-tryptophan.

This article explains why does l-tryptophan help you sleep.

Let’s start off by explaining what tryptophan is and how it works.

What is L-Tryptophan

L-tryptophan is an amino acid. Amino acids are building blocks of protein.

L-tryptophan naturally occurs in many foods, particularly those that contain proteins.

Besides making proteins, amino acids such as tryptophan have other important roles in the body.

One of these roles is to make the neurotransmitter serotonin.

Found in the brain and the gut, serotonin is a chemical messenger that regulates sleep, mood, and appetite.

Serotonin is also a precursor to melatonin, which is the hormone that helps you fall asleep. Do you see where this goes?

How Does it Work?

Okay, you might be wondering how does l-tryptophan convert to melatonin, the sleep hormone?

To start the process, your body converts tryptophan into 5-HTP. This is a molecule which is directly used by the body to create serotonin.

Once 5-HTP converts to serotonin, there’s just one step of conversion left, which is serotonin turning to melatonin.

You may be asking, how does your body know when it’s time to convert serotonin to melatonin?

It’s simple. When the sun is out, your body produces serotonin. When it gets dark, serotonin converts to melatonin – this is how your body tells you it’s time to sleep.

Why L-Tryptophan Does Make You Sleep?

Now that you know how l tryptophan works, it’s easy to see why it makes you sleep.

When you eat food rich in l-tryptophan or take a tryptophan supplement, your levels of serotonin and melatonin raise.

In other words, increased levels of l-tryptophan lead to higher levels of the sleeping hormone. Making you want to hit the sack. (4, 5)

teddy bear by a laptop at night

Can Low L-Tryptophan Levels Cause Insomnia?

Since l-tryptophan is a building block for 5-HTP, and consequently serotonin and melatonin, low levels of this amino acid could give you insomnia.

But that isn’t the only problem with low tryptophan.

Other Side Effects of Low L-Tryptophan

Anxiety and Depression

A number of studies showed that people with depression usually have low tryptophan levels. (6, 7)

To further prove this, experts deliberately altered tryptophan blood levels in volunteers by changing the amino acid contents of their food.

After this, the researchers exposed these volunteers to a stressful event twice. One time, when they had normal tryptophan levels. And later, when their blood tryptophan levels were low.

The study found that volunteers had much higher anxiety and nervousness when their tryptophan levels were low. (8, 9)

Looking at these results, it’s clear that low tryptophan can cause more than just a poor night of sleep. It can also negatively affect your day to day life.

On the other hand, studies show that supplementing with tryptophan reduces anxiety and improves socialization between people. (10)

Cognition and Memory Issues

It turns out, l-tryptophan deficiency also leads to memory and learning impairment.

Studies show that people who had low levels of this amino acid experienced trouble remembering things, or learning new information. (11, 12)

To prevent this from happening to you, here are some of the best l-tryptophan sources:

L-Tryptophan Sources

Perhaps the most famous source of l-tryptophan is turkey, which is one of the symbols of Thanksgiving. But there are other foods that contain tryptophan. These include (13):

  • Poultry
  • Bananas
  • Honey
  • Eggs
  • Elk
  • Crab
  • Salmon
  • Spinach
  • Milk
  • Soy

You can also take tryptophan supplements – up to 3g per day is shown as a safe and effective dosage for most people. However, always start with a lower dosage and go from there. I suggest starting at 1g per day and see how you feel.

turkey thanksgiving

Is L-Tryptophan Safe?

Tryptophan is naturally occurring in many foods. As such, it’s safe to ingest in normal quantities you’d get from food.

An average diet contains 1g of tryptophan a day. However, some people choose to take tryptophan supplements in the 3-5g dosage range. This is also shown to be safe. (14)

Side effects of l-tryptophan are rare. This amino acid has been studied for over 50 years. During this period, it’s been discovered that only a small percentage of people may experience dizziness and nausea when taking high doses of tryptophan (more than 3-5 grams per day). (14)

That said, I don’t think it’s smart to combine tryptophan with certain medications. Particularly, anti-depressants.

Since both antidepressants and tryptophan influence serotonin in the brain, combining them can, in extreme cases, cause serotonin syndrome. This is sometimes a fatal condition where too much serotonin is floating in your brain. (15)

Therefore, make sure to talk with your doctor about tryptophan if you’re on any kind of medication – even if it’s not an antidepressant. Better be safe than sorry.

Wrapping Up

Your body uses l-tryptophan as a building block for proteins, along with other molecules. These include serotonin and melatonin.

While serotonin affects your appetite, mood, and cognition, melatonin affects your sleep-wake cycle. Your body produces serotonin during the daytime and converts it into melatonin (the sleep hormone) when it gets dark.

However, if there’s not enough l-tryptophan to start with, your brain won’t be able to produce optimal levels of serotonin and melatonin. This can lead to a number of problems. Not only insomnia, but also anxiety, depression, and memory impairments.

While tryptophan is naturally occurring in many foods, some people decide to supplement it to improve their sleep quality. Studies show that up to 3g of tryptophan per day is perfectly safe. Side effects like nausea might occur at higher doses in some people.

However, don’t take tryptophan if you are under antidepressants. Both the l-tryptophan and antidepressants affect your serotonin system. Taking them both can potentially cause serotonin syndrome. This is a life-threatening condition.

That said, l-tryptophan itself is a safe and essential amino acid for your health, mood, and sleep. If you have problems with insomnia, increasing your tryptophan intake either through food or supplements might be a good idea.


  1. Effect of 1 Week of Sleep Restriction on Testosterone Levels in Young Healthy Men. (source)
  2. Sleep Deficiency and Deprivation Leading to Cardiovascular Disease. (source)
  3. Medications for the Treatment of Sleep Disorders: An Overview. (source)
  4. The influence of intravenous L-tryptophan on plasma melatonin and sleep in men. (source)
  5. Tryptophan increases nocturnal rest and affects melatonin and serotonin serum levels in old ringdove. (source)
  6. Total and free tryptophan concentration in the plasma of depressive patients. (source)
  7. Decreased plasma tryptophan levels in major depression. (source)
  8. Tryptophan depletion causes a rapid lowering of mood in normal males. (source)
  9. Effects of tryptophan depletion on anxiety and on panic provoked by carbon dioxide challenge. (source)
  10. Tryptophan supplementation modulates social behavior: A review. (source)
  11. Tryptophan depletion in normal volunteers produces selective impairment in memory consolidation. (source)
  12. Effects of acute tryptophan depletion on memory, attention and executive functions: a systematic review. (source)
  13. Self-Nutrition Data, foods highest in tryptophan. (source)
  14. Effects and side effects associated with the non-nutritional use of tryptophan by humans. (source)
  15. Animal models of the serotonin syndrome: a systematic review. (source)

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One Comment

  • Jon July 1, 2020

    Excellent information