Tryptophan

Tryptophan is an amino acid that has several important functions in the human body. It comes in two types, L-tryptophan and D-tryptophan, which are differentiated by the orientation of the molecule. It is primarily a biosynthesizer of proteins and is used by animals and plants to carry out various biological functions. It also plays a role in a person’s sleep cycle by creating niacin, a precursor to the neurotransmitter serotonin, which impacts sleep, mood, and cognition. Tryptophan also helps make melatonin, which also influences a person’s sleep. Tryptophan cannot be naturally produced in the body and must be supplied in the diet of humans. For this reason, it is considered an essential amino acid. The National Academy of Medicine recommends a daily intake of five milligrams per kilogram of body weight for tryptophan. People sometimes take tryptophan in supplement form to help with certain mental disorders. It is also used to help a person quit smoking or to enhance athletic performance. Scientific evidence supporting the use of tryptophan for these issues is scarce, however. Some experts worry that tryptophan supplementation can have adverse effects on a person.

Background

Tryptophan is an amino acid and is important in the development and functioning of multiple organs throughout the body. An amino acid is a building block of proteins. Tryptophan is one of twenty-two amino acids and is the least plentiful in the body. It cannot be naturally produced in the body and therefore requires ingestion of protein-based plant or animal foods, such as eggs, milk, poultry, fish, red meat, peanuts, almonds, and buckwheat. It is found in high amounts in chocolate and oats. Many people think there is a high amount of tryptophan in turkey and that is why they feel sleepy after eating a large turkey dinner. This is not the case, however, and tryptophan levels in turkey are similar to those found in other poultry. Tryptophan is considered a natural sedative, but this is more in regards to its role in serotonin production.

Tryptophan plays an important biological role in the body. Alongside the amino acid tyrosine, it helps anchor proteins to the membranes of cells. Tryptophan is also converted into an amino acid called 5-hydroxy-tryptophan (5-HTP), which acts as a chemical precursor and metabolite in the biosynthesis of the neurotransmitter called serotonin. A neurotransmitter is a chemical messenger that sends signals from one neuron to another, creating a biological reaction in the body. Serotonin is a complex neurotransmitter that has many functions throughout the body, influencing physiological and behavioral tasks. A certain amount of serotonin in the body is necessary for consistent normal bodily function. The benefits of increased serotonin levels include healthier and better-quality sleep, relief from anxiety and depression, better moods, and a better threshold for pain. Metabolization of the nutrients iron, riboflavin, vitamin B6, niacin, and glutathione by tryptophan is also necessary to produce serotonin. Niacin is an especially important metabolite of tryptophan, and is synthesized via products of tryptophan degradation.

Tryptophan is also a precursor to the hormone melatonin. Hormones are chemicals found in the body that regulate various biological functions. They often act as neurotransmitters. In humans, the pineal gland is the center of melatonin production. Melatonin is synthesized from serotonin and helps regulates a person’s sleep cycle and wakefulness. Tryptophan’s metabolization of vitamin B6 also contributes to the body’s wakefulness and is important to a person’s energy metabolism.

Overview

Tryptophan is essential for normal growth in infants and serves as a blood nitrogen balancer in adults. Deficiencies in tryptophan levels can cause health issues, and a number of conditions and diseases are characterized by low levels of tryptophan. Low levels are usually the result of an imbalanced diet but can also be caused by internal malfunctions. When the body does not absorb fructose properly, it can cause tryptophan absorption problems in the intestine. If tryptophan cannot be absorbed properly, it cannot enter the bloodstream and carry out its functions. Low levels of tryptophan in the blood can lead to depression. Ensuring you get enough tryptophan in your diet is important to your overall health. Tryptophan-deficient diets can cause diseases such as pellagra, a deficiency disease caused by a lack of niacin, which is biosynthesized from tryptophan. This disease is characterized by symptoms such as dermatitis, diarrhea, and dementia. Improper tryptophan absorption can also cause a condition known as Hartnup’s disease, which causes skin rashes, movement coordination problems, and psychological symptoms such as psychosis and depression.

Some people take tryptophan as a dietary supplement, mainly as a means of increasing serotonin production in the body. Increased levels of serotonin can ease symptoms of anxiety and depression and help a person sleep better. Studies have also shown that taking tryptophan supplements can help a person quit smoking when taken in tandem with conventional treatments. Some people also take the supplement to improve their athletic ability, mental functions, and overall focus. Studies show that tryptophan levels are often lower in children with attention deficit-hyperactivity disorder (ADHD), but tryptophan supplementation has not proven to affect change in such cases thus far. Insufficient evidence also exists linking tryptophan intake to improved athletic ability. Although some research has shown that taking the supplement several days in advance can improve power during exercise, taking the supplement during exercise did not improve endurance. Research has also suggested tryptophan supplementation may help ease symptoms of depression and can be used to treat sleep disorders. The US Food and Drug Administration (FDA) has warned that tryptophan supplementation should be considered with caution as it may be unsafe and cause health issues.

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