Everyone knows that a good night's sleep prepares you for the day.

In addition, 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 is necessary to make proteins and other important molecules in your body, including those needed for optimal sleep and mood.

This article describes the effects of tryptophan on these fundamental areas of your life.

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

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

For example, they are necessary to make several important molecules that aid in signaling.

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 multiple organs including the brain and gut. In the brain, it specifically influences sleep, perception and mood ( 4 , 5 ).

Melatonin is now a hormone that is primarily involved in your sleep-wake cycle ( 6 ).

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

Although tryptophan has many functions, its influence on the brain is particularly noteworthy.

Several studies have shown that lower than normal levels of tryptophan can occur in depression ( 7 , 8 ).

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

By lowering tryptophan levels, researchers can learn about their functions. To do this, the study participants ingest large amounts of amino acids with or without tryptophan (9).

In one such study, 15 healthy adults were exposed twice to a stressful environment - once with normal tryptophan blood levels and once with low levels ( 10 ).

Researchers found that anxiety, tension, and nervousness were higher when participants had low levels of tryptophan.

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

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

On the other hand, taking tryptophan can promote good social behavior ( 13 )

The change in tryptophan can affect different aspects of cognition.

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

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

An extensive study also found that lower levels of tryptophan negatively affected cognition and memory ( 15 ).

Memory associated with events and experiences can be particularly impaired.

These effects are probably due to the fact that serotonin production decreases with decreasing tryptophan levels ( 15 ).

Tryptophan can be converted in the body 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 serotonin or 5-HTP ( 15 ).

In other words: an increase in levels can lead to increased 5-HTP and serotonin ( 17 , 18 ).

Serotonin and 5-HTP affect many processes in the brain, and disruption to their normal actions can affect depression and anxiety ( 5 ).

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

In addition, serotonin influences the learning processes in the brain ( 20 ).

Treatment with 5-HTP may also help increase serotonin and improve mood and panic 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 ).

Once serotonin has been produced in the body from tryptophan, 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 ).

Melatonin is not only naturally present in the body, it is also a popular dietary supplement found in various foods such as tomatoes, strawberries and grapes ( 22 ).

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

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

One study found that eating tryptophan-enriched muesli for breakfast and dinner helped adults fall asleep and sleep longer compared to standard muesli (25).

Anxiety and depression symptoms were also reduced, and it is likely that tryptophan helped increase serotonin and melatonin.

Other studies have also shown that taking melatonin can improve the amount and quality of sleep ( 26 , 27 ).

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

Because of this, you're getting some tryptophan every time you eat high-protein foods.

Your intake will depend on how much protein you consume and what protein sources you consume.

Some foods are particularly rich in tryptophan, including poultry, shrimp, eggs, and crab ( 28 ).

A typical diet has been estimated to provide approximately 1 gram per day ( 29 ).

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

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

It is estimated that a typical diet contains 1 gram per day, but some individuals choose to dose up to 5 grams per day ( 29 ).

Its possible side effects have been studied for over 50 years and very few have been reported.

However, side effects such as nausea and dizziness have occasionally been reported at doses above 50 mg per kilogram body weight or 3.4 grams in a 68 kg adult ( 29 ).

Side effects may be more pronounced when tryptophan or 5-HTP is taken along with medications that affect serotonin levels, such as antidepressants.

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

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

If you are taking any medications that affect your serotonin levels, you should consult your doctor before taking tryptophan or 5-HTP supplements.

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

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

Therefore, low levels of tryptophan can lower serotonin and melatonin levels, which is detrimental.

Although tryptophan is found in protein foods, it is often taken as a supplement. At moderate doses, it's probably safe. However, side effects may occasionally occur.

These side effects can become more serious if you are also taking medicines that affect your serotonin levels, such as antidepressants.

Some of the molecules that 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 an increased intake of this amino acid or the molecules it produces.