L-tryptophan and 5-HTP for sleep: trend versus evidence

L-tryptophan is an essential amino acid that we normally take in with protein in our diet, the CDC notes; some people use it as a supplement, for example for insomnia. (CDC — Eosinophilia-Myalgia Syndrome, MMWR 1989) The body can turn it — like its relative 5-hydroxytryptophan (5-HTP) — into melatonin. According to the US NCCIH, both supplements have sedative effects, but it is unclear how they work, and there is very little data on their effect on insomnia. (NCCIH — Sleep Disorders and Complementary Health Approaches)

This article summarises what research has shown so far; it is not a diagnosis or a treatment.

What studies show

• In its 2017 guideline the American Academy of Sleep Medicine (AASM) suggests that clinicians not use tryptophan to treat trouble falling or staying asleep in adults (a weak recommendation). Only one study had usable data, and it showed no clinically significant benefit; the authors judged that possible harms may outweigh the benefits. (AASM guideline, J Clin Sleep Med 2017)
• A pooled analysis that its authors presented in 2021 as a conference abstract found less time awake after falling asleep with tryptophan, but no effect on total sleep time, time to fall asleep or sleep efficiency. Only four studies could be combined in the calculation. (Sutanto et al., Curr Dev Nutr 2021)
• For 5-HTP and sleep, none of the sources we cite offers convincing evidence; NCCIH describes the data as very limited. (NCCIH — Sleep Disorders and Complementary Health Approaches)

Safety

• In 1989 the CDC described the first patients in the US with a newly recognised illness — eosinophilia and severe muscle pain — who had been taking L-tryptophan; the US FDA then advised consumers to stop using products containing it. (CDC — Eosinophilia-Myalgia Syndrome, MMWR 1989)
• According to NCCIH, the outbreak of eosinophilia-myalgia syndrome (EMS) was traced to contaminated synthetic L-tryptophan from a single manufacturer. EMS is rare but can cause severe, disabling complications and even death. Because the two are related, 5-HTP has been under close watch too; analyses of several sources found no similar contaminants. (NCCIH — Sleep Disorders and Complementary Health Approaches)
• NCCIH warns that L-tryptophan taken with medicines that affect serotonin may cause life-threatening serotonin toxicity. If you take any medicines, talk to a doctor or pharmacist before trying a supplement. (NCCIH — Sleep Disorders and Complementary Health Approaches)
• The US FDA points out that in the US it does not approve dietary supplements for safety or effectiveness before they are sold, that calling a product "natural" does not ensure it is safe, and that some supplements can interact with medicines. (FDA — FDA 101: Dietary Supplements)

What works for insomnia

• According to the AASM, the standard treatment for chronic insomnia is cognitive behavioural therapy for insomnia (CBT-I). (AASM guideline, J Clin Sleep Med 2017)
• A GP may offer you CBT, the NHS says — with a therapist or as an online programme. (NHS — Insomnia)

When to see a doctor

• The NHS advises seeing a GP if changing your sleep habits hasn't helped, you have had trouble sleeping for months, or insomnia is affecting your daily life. (NHS — Insomnia)
• Tell your doctor about any supplements you take — they can look after you better. (NCCIH — Sleep Disorders and Complementary Health Approaches)
• If you have a bad reaction after taking a supplement, stop using it and seek medical advice. (FDA — FDA 101: Dietary Supplements)
• An AI health check is not a medical review. This article is not medical advice.

Takeaways

1. L-tryptophan and 5-HTP are substances the body can turn into melatonin; as supplements they are offered for sleep.
2. There is very little evidence that they help with insomnia; the AASM advises against tryptophan for insomnia.
3. The 1989 EMS outbreak and the risk of serotonin toxicity with some medicines are reasons for caution.
4. "Natural" does not mean safe — talk to a doctor or pharmacist before taking a supplement, especially if you take medicines.
5. Insomnia lasting months → GP; the standard treatment is CBT-I.

We take in tryptophan from ordinary food every day — as a sleep supplement, though, it has not yet convinced.