Overview

L-tryptophan is found in foods that contain protein and is also available over the counter as a dietary supplement. It is used for many different reasons, but its benefits are not well defined. Common side effects may include dizziness, sleepiness, dry mouth, nausea, and tremors. Before taking L-tryptophan, make sure to tell your health care provider about any health conditions you have or medicines you are taking.

Uses

What is L-tryptophan used for?

L-tryptophan is used for many different reasons. However, its benefits are not well defined. Some common reasons that people use L-tryptophan include the following.

• Anxiety
• Depression, including seasonal affective disorder (SAD)
• Sleep problems

Note: The FDA has not reviewed L-tryptophan for safety and effectiveness. Learn more about dietary supplements here.

How does L-tryptophan work (mechanism of action)?

L-tryptophan is an amino acid, which is a building block for protein. Your body uses L-tryptophan to make protein and produce important chemicals and hormones, such as serotonin, melatonin, and niacin.

Although your body needs L-tryptophan to function, it cannot make L-tryptophan on its own. As a result, you must get it from your diet. L-tryptophan is naturally found in protein-rich foods, including meat, cheese, eggs, fish, tofu, and yogurt. Most people in the United States get enough L-tryptophan from the proteins in their diet.

Your body makes the brain chemical serotonin from L-tryptophan. Serotonin plays an important role in brain function, behavior, and mood. But taking L-tryptophan does not always seem to increase serotonin levels in the brain. The benefits of L-tryptophan for reducing symptoms of anxiety or depression are not well defined.

Your body also uses L-tryptophan to make melatonin. Melatonin is a hormone that helps your body set its circadian rhythm, which is like its internal clock. Your brain releases more melatonin when it is dark out, which signals your body to sleep. Taking high doses of L-tryptophan may make some people feel sleepy. But it is not clear what dose of L-tryptophan is needed, or whether it helps with sleep problems.

How should I store L-tryptophan?

You should store L-tryptophan according to the product label. Most dietary supplements should be kept in a cool, dry location that is out of the reach of children and pets and not in direct sunlight.

Side Effects

What are the most common side effects of L-tryptophan?

The most common side effects of L-tryptophan are listed below. These side effects may vary depending on the dose you are taking or the specific product you are using. Tell your health care provider if you have any of these side effects that bother you.

• Dizziness
• Dry mouth
• Nausea
• Sleepiness
• Tremors

There may be other side effects of L-tryptophan that are not listed here. Contact your health care provider if you think you are having a side effect of a supplement. In the U.S., you can report side effects to the FDA at www.safetyreporting.hhs.gov or by calling 888-SAFEFOOD (888-723-3366). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of L-tryptophan?

While less common, the most serious side effects of L-tryptophan are described below, along with what to do if they happen.

Severe Allergic Reactions. L-tryptophan may cause allergic reactions, which can be serious. Stop taking L-tryptophan and get help right away if you have any of the following symptoms of a serious allergic reaction.

• Breathing problems or wheezing
• Racing heart
• Fever or general ill feeling
• Swollen lymph nodes
• Swelling of the face, lips, mouth, tongue, or throat
• Trouble swallowing or throat tightness
• Itching or skin rash
• Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
• Nausea or vomiting
• Dizziness, feeling lightheaded, or fainting
• Stomach cramps
• Joint pain

Precautions

Who should not use L-tryptophan?

Allergies to Ingredients. People who are allergic to any of the following should not take L-tryptophan.

• L-tryptophan
• Tryptophan
• Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific L-tryptophan products they stock.

What should I know about L-tryptophan before using it?

L-tryptophan is a dietary supplement. It cannot be marketed to treat or cure a disease.

Read and follow the directions on the specific product you are taking, or take it as recommended by your health care provider.

Keep L-tryptophan out of the reach of children.

L-tryptophan can affect your alertness or coordination. Do not drive or do other activities that require alertness or coordination until you know how L-tryptophan affects you.

Some people use L-tryptophan for sleep problems. If you have sleep problems, it is important to make sure that you have the right sleeping conditions and good sleep-related habits. This is known as good sleep hygiene. Learn more about sleep hygiene here.

In the late 1980s, some people who took L-tryptophan supplements had a serious condition called eosinophilia myalgia syndrome (EMS). This seems to have been caused by harmful chemicals found in certain L-tryptophan products. These serious cases led the FDA to ban L-tryptophan products that were made outside of the United States. L-tryptophan itself did not cause this serious condition. But the FDA has not tested L-tryptophan products to confirm that they contain the ingredients stated on their labels. Some dietary supplements have been tested by third-party organizations to confirm that they contain the ingredients listed on their labels and do not contain any harmful chemicals. Learn more about how to choose a safe dietary supplement product here.

What should I tell my health care provider before using L-tryptophan?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if L-tryptophan is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions.Tell your health care provider if you have any of the following.

• Mental health problems, including depression
• Kidney problems

Other Medicines and Supplements.L-tryptophan may interact with other medicines and supplements. Before taking L-tryptophan, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how L-tryptophan could affect pregnancy or harm an unborn baby. Tell your health care provider if you are pregnant or plan to become pregnant.

Breastfeeding. It is not known if L-tryptophan passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does L-tryptophan interact with foods or drinks?

There are no known interactions between L-tryptophan and foods or drinks.

It is unknown if drinking alcohol will affect L-tryptophan, but drinking alcohol while taking L-tryptophan may increase your risk for sleepiness or dizziness.

Does L-tryptophan interact with medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking L-tryptophan.

• A monoamine oxidase inhibitor (MAOI) within the past two weeks, which is a medicine usually used for depression or Parkinson’s disease
• A selective serotonin reuptake inhibitor (SSRI), such as fluoxetine, paroxetine, or sertraline, which is a medicine commonly used for anxiety and depression
• A serotonin and norepinephrine reuptake inhibitor (SNRI), such as duloxetine or venlafaxine, which is a medicine commonly used for anxiety and depression
• A tricyclic antidepressant, such as amitriptyline, nortriptyline, or protriptyline, even if it is not used for depression

The interactions between L-tryptophan and medicines are not fully understood. As with most dietary supplements, the research on drug interactions with L-tryptophan is incomplete. Always check with your health care provider before taking L-tryptophan with any medicines.

Dosing

What should I do if I accidentally use too much L-tryptophan?

If you or someone else has used too much L-tryptophan, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

L-tryptophan is available in a wide range of doses. Read the product label closely and speak with a health care provider about how to use L-tryptophan safely. Do not take double or extra doses, even if you miss a dose.