Everyone knows that a good night’s sleep prepares you to face the day.

What’s more, several nutrients promote good sleep quality and support your mood.

Tryptophan, an amino acid found in many foods and supplements, is one of them.

It’s necessary for making proteins and other important molecules in your body, including some that are essential for optimal sleep and mood.

This article discusses the effects of tryptophan on these fundamental parts of your life.

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Tryptophan is one of many amino acids found in foods that contain protein.

In your body, amino acids are used to make proteins but also serve other functions (1).

For example, they are necessary to produce several important molecules that help transmit signals.

In particular, tryptophan can be converted into a molecule called 5-HTP (5-hydroxytryptophan), which is used to make serotonin and melatonin (2, 3).

Serotonin affects several organs, including the brain and intestines. In the brain specifically, it influences sleep, cognition and mood (4, 5).

Meanwhile, melatonin is a hormone that’s most notably involved in your sleep-wake cycle (6).

Overall, tryptophan and the molecules it produces are essential to the optimal functioning of your body.

Summary Tryptophan is an amino acid that can be converted into several important molecules, including serotonin and melatonin. Tryptophan and the molecules it produces influence many functions in the body, including sleep, mood and behavior.

Although tryptophan has many functions, its impact on the brain is particularly notable.

Low Levels Are Associated With Mood Disorders

Several studies have shown that those experiencing depression may have tryptophan levels that are lower than normal (7, 8).

Other research has examined the effects of altering blood levels of tryptophan.

By lowering tryptophan levels, researchers can learn about its functions. To do so, study participants consume large amounts of amino acids, with or without tryptophan (9).

One such study exposed 15 healthy adults to a stressful environment twice — once when they had normal tryptophan blood levels and once when they had low levels (10).

The researchers found that anxiety, tension and feelings of nervousness were higher when the participants had low tryptophan levels.

Based on these results, low levels of tryptophan could contribute to anxiety (11).

They may also increase aggression and impulsiveness in aggressive individuals (12).

On the other hand, supplementing with tryptophan may promote good social behavior (13).

Summary Research has shown that low levels of tryptophan may contribute to mood disorders, including depression and anxiety.

Low Levels May Impair Memory and Learning

Altering levels of tryptophan can influence several aspects of cognition.

One study found that when tryptophan levels were lowered, long-term memory performance was worse than when levels were normal (14).

These effects were seen regardless of whether the participants had a family history of depression.

Additionally, a large review found that lower tryptophan levels negatively impacted cognition and memory (15).

Memory linked to events and experiences may be particularly impaired.

These effects are likely due to the fact that as tryptophan levels are lowered, serotonin production decreases (15).

Summary Tryptophan is important for cognitive processes because of its role in serotonin production. Low levels of this amino acid can impair your cognition, including your memory of events or experiences.

Serotonin Is Responsible for Many of Its Effects

In the body, tryptophan can be converted into the molecule 5-HTP, which then forms serotonin (14, 16).

Based on numerous experiments, researchers agree that many of the effects of high or low tryptophan levels are due to its effects on serotonin or 5-HTP (15).

In other words, increasing its levels can lead to increased 5-HTP and serotonin (17, 18).

Serotonin and 5-HTP affect many processes in the brain, and interference with their normal actions may impact depression and anxiety (5).

In fact, many drugs designed to treat depression modify the action of serotonin in the brain to increase its activity (19).

What’s more, serotonin influences processes in the brain that are involved in learning (20).

Treatment with 5-HTP can also help increase serotonin and improve mood and panic disorders, as well as insomnia (5, 21).

Overall, the conversion of tryptophan to serotonin is responsible for many of its observed effects on mood and cognition (15).

Summary The importance of tryptophan is likely due to its role in serotonin production. Serotonin is essential for the proper functioning of the brain, and low tryptophan levels reduce the amount of serotonin in the body.

Once serotonin has been produced from tryptophan in the body, it can be converted into another important molecule — melatonin.

In fact, research has shown that increasing tryptophan in the blood directly increases both serotonin and melatonin (17).

In addition to being found naturally in the body, melatonin is a popular supplement and found in several foods, including tomatoes, strawberries and grapes (22).

Melatonin influences the sleep-wake cycle of the body. This cycle impacts many other functions, including the metabolism of nutrients and your immune system (23).

Several studies have shown that increasing tryptophan in the diet can improve sleep by increasing melatonin (24, 25).

One study found that eating tryptophan-enriched cereal at breakfast and dinner helped adults fall asleep faster and sleep longer, compared to when they ate standard cereals (25).

Symptoms of anxiety and depression were also reduced, and it is likely that the tryptophan helped increase both serotonin and melatonin.

Other studies have also shown that taking melatonin as a supplement can improve sleep quantity and quality (26, 27).

Summary Melatonin is important to the body’s sleep-wake cycle. Increasing tryptophan intake can lead to higher levels of melatonin and may improve sleep quantity and quality.

Many different protein-containing foods are good sources of tryptophan (28).

Because of this, you get some of this amino acid almost any time you eat protein.

Your intake depends on how much protein you consume and which protein sources you eat.

Some foods are particularly high in tryptophan, including poultry, shrimp, eggs, elk and crab, among others (28).

It has been estimated that a typical diet provides approximately 1 gram per day (29).

You can also supplement with tryptophan or one of the molecules it produces, such as 5-HTP and melatonin.

Summary Tryptophan is found in foods that contain protein or supplements. The specific amount of it in your diet varies on the amount and types of protein you eat, but it has been estimated that a typical diet provides about 1 gram per day.

If you want to improve your sleep quality and well-being, tryptophan supplements are worth considering. However, you also have other options.

You may choose to supplement with molecules that are derived from tryptophan. These include 5-HTP and melatonin.

If you take tryptophan itself, it may be used in other bodily processes besides making serotonin and melatonin, such as protein or niacin production. That’s why supplementing with 5-HTP or melatonin may be a better choice for some people (5).

Those who want to improve their mood or cognition may choose to take tryptophan or 5-HTP supplements.

Both of these can increase serotonin, although 5-HTP can be converted to serotonin more quickly (5).

What's more, 5-HTP can have other effects, such as decreasing food consumption and body weight (30, 31).

Doses of 5-HTP may range from 100–900 mg per day (31).

For those who are most interested in promoting sleep, supplementing with melatonin may be the best choice (27).

Doses of 0.5–5 mg per day have been used, with 2 mg being the most common dose (32).

For those who take tryptophan itself, doses of up to 5 grams per day have been reported (29).

Summary Tryptophan or its products (5-HTP and melatonin) can be taken individually as dietary supplements. If you choose to take one of these supplements, the best choice depends on the symptoms you are targeting.

Since tryptophan is an amino acid found in many foods, it is assumed to be safe in normal quantities.

It's estimated that a typical diet contains 1 gram per day, but some individuals choose to supplement with doses of up to 5 grams per day (29).

Its possible side effects have been examined for over 50 years, and very few of them have been reported.

However, occasional side effects like nausea and dizziness have been reported at doses above 50 mg per kilogram of body weight, or 3.4 grams for a 150-pound (68-kg) adult (29).

Side effects may be more prominent when tryptophan or 5-HTP is taken along with drugs that influence serotonin levels, such as antidepressants.

When the activity of serotonin is excessively increased, a condition called serotonin syndrome can result (33).

It can cause several symptoms, including sweating, tremors, agitation and delirium (29).

If you are taking any medications that affect your serotonin levels, consider consulting your physician before taking tryptophan or 5-HTP supplements.

Summary Studies on tryptophan supplements report minimal effects. However, occasional nausea and dizziness have been observed at higher doses. Side effects can become more severe when taking medications that influence serotonin levels.

Your body uses tryptophan to make several important molecules, including serotonin and melatonin.

Serotonin influences your mood, cognition and behavior, while melatonin influences your sleep-wake cycle.

Thus, low tryptophan levels may decrease serotonin and melatonin levels, leading to detrimental effects.

Although tryptophan is found in protein-containing foods, it’s often taken as a supplement. It is likely safe at moderate doses. However, occasional side effects may occur.

These side effects could become more serious if you're also taking medication that influences your serotonin levels, such as antidepressants.

Several of the molecules tryptophan produces in the body, including melatonin, are also sold as supplements.

Overall, tryptophan is a crucial amino acid for your health and well-being. Certain individuals may benefit from increasing their intake of this amino acid or the molecules it produces.