Product Reviews
L-Tryptophan and 5-Hydroxytryptophan (5-HTP) Supplements

Reviewed and edited by Tod Cooperman, M.D. Tod Cooperman, M.D.
Initial Posting: 7/27/2018 Last update: 1/19/2019
L-Tryptophan and 5-HTP (5-Hydroxy-L-tryptophan) Supplements Reviewed By
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  • What do they do? L-tryptophan is an essential amino acid naturally found in meats and other foods. It is converted in the body to 5-HTP (which is not found in foods), which is then converted to serotonin and melatonin (see What It Is). L-tryptophan can promote sleep, while 5-HTP has been used as an antidepressant, although this effect has not been well-established. Both have been proposed for other uses based on preliminary evidence (see What It Does).
  • Are they safe? L-tryptophan from a specific manufacturer caused hundreds of cases of a serious immune disorder, eosinophilia-myalgia syndrome (EMS), in the late 1980s. A more pure form is now sold that seems to be much safer. However, there is still some risk with even pure L-tryptophan, particularly at high doses. 5-HTP in supplements is generally safe, but rare cases of EMS have also been reported. (See Concerns and Cautions).
  • Best choice? CL tested all supplements for a range of impurities. Among those that passed testing and provided the best value, CL selected a Top Pick for L-Tryptophan and a Top Pick for 5-HTP.
  • How to take them? L-tryptophan is taken for sleep at a dose of about 1 gram (1,000 mg) shortly before bedtime, while other uses have involved higher doses. 5-HTP is taken at a daily dose of about 300 mg to 900 mg depending on the use, and divided during the day. (See What to Consider When Using).
  • Cautions: In addition to the potential risk of EMS and some mild side effects, these supplements should be used with caution in people taking medications that affect serotonin, such as some antidepressants and migraine medications (see Concerns and Cautions).
What It Is:
L-Tryptophan is an essential amino acid, meaning that it must be obtained from foods, because the body is unable to make it. L-Tryptophan is found in many protein-rich foods, including cheese, chicken, eggs, fish, milk, nuts, soy, tofu, and turkey. The amount of L-tryptophan generally obtained from a 100 gram (3.5 ounce) serving of these foods ranges from about 100 mg to 500 mg (see Tryptophan in Foods table below). In foods, the L-tryptophan is bound to other amino acids. Most supplements currently on the market provide L-tryptophan as a single amino acid, typically at 500 mg per serving.

5-hydroxytryptophan (L-5-hydroxytryptophan or oxitriptan) is also an amino acid, but is not essential and is not found in appreciable amounts in the diet. 5-HTP is created in the body from tryptophan. In supplements, 5-HTP is typically extracted from seeds of Griffonia simplicifolia.

What It Does:
Through a series of steps, the body uses L-tryptophan to first make 5-HTP and then serotonin and melatonin, neurotransmitters that promote good mood and sleep.

As a supplement, L-tryptophan can increase sleepiness and decrease the time needed to fall asleep — although it has not been shown to increase sleep time. Best results have been found in people with mild insomnia or needing longer-than-average times to fall asleep. Results have been mixed or negative in entirely normal subjects, severe insomniacs, and people with serious medical or psychiatric illness (Hartmann, J Psychiatr Res. 1982).

Some human research finds that L-tryptophan might help reduce feelings of unhappiness, irritability and mood swings in women with premenstrual dysphoric disorder (PMDD). Limited human research suggests that it might be useful for treating depression, seasonal affective disorder (SAD), and sleep apnea. For example, improvements in symptoms were reported in two of three people with treatment-resistant unipolar depression and borderline personality disorder who were given 1 to 2 grams of L-tryptophan daily (Thomas, Adv Integ Med 2015). Other human research indicates that L-tryptophan might help reduce cigarette cravings in people who are quitting smoking. Well-designed and conducted human studies are needed to determine if L-tryptophan is effective or ineffective for all of these conditions.

For Depression:
5-HTP is a direct pre-cursor to serotonin and is able to cross the blood-brain barrier, permitting it access to the central nervous system where the conversion to serotonin occurs. Due to its ability to raise serotonin levels, like antidepressant drugs, the primary use of 5-HTP is for depression. Several small studies have compared 5-HTP to standard antidepressants. One 6-week study found 5-HTP of equal benefit to fluvoxamine (Luvox) at 50 mg three times daily, and 5-HTP caused fewer side effects than fluvoxamine. However a drug comparison study like this does not rule-out a placebo effect. As there are no published, placebo-controlled studies of 5-HTP for treating depression, its role remains unproven.

Other Uses:
Some, but not all, studies have found that 5-HTP may help prevent migraines (See Encyclopedia article on 5-HTP), although not tension headaches (See What to Consider When Using below for dosage). Small studies of just several weeks in duration have also indicated that 5-HTP may help with weight loss by causing people to consume fewer calories and feel full after eating. A study also found that 5-HTP can help people with fibromyalgia, a condition characterized by tender muscles, fatigue, and sleep disturbances and which is often treated with antidepressants. In people suffering from anxiety disorders, 5-HTP was found to be effective, but not as effective as the drug clomipramine.

See the article about 5-hydroxytryptophan in the Encyclopedia on this site for more information about clinical studies with 5-HTP.

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