Sleep
L-Tryptophanand Sleep
All three sources here measured higher sleep.
How sure anyone can be
Low certainty, level 2 of 4Further research is likely to change this.
The most certain of the three findings here; each record carries its own.
The numbers reported
- -1.08 standardised effect size
- standardised effect size wake after sleep onset
- -5.188
- minutes objective wake-after-sleep-onset regression coefficient
- -50
- approximate percent sleep-latency reduction
None of these sources gave a likely range — the band the real answer probably sits in — so how precise these numbers are is still an open question here.
Three sources, newest first
What we read is the published abstract, not the full paper, so a blank below may still be printed in the paper itself. A person went through the criteria and recorded which brought the rating down. Their reasons are not on record here.
Systematic review, 2022
Low certainty, level 2 of 4The impact of tryptophan supplementation on sleep quality: a systematic review, meta-analysis, and meta-regression.
Sutanto CN, Loh WW, Kim JE. The impact of tryptophan supplementation on sleep quality: a systematic review, meta-analysis, and meta-regression. Nutr Rev. 2022. doi:10.1093/nutrit/nuab027. PMID:33942088.
- Number reported
- -1.08 standardised effect size
- Which way it went
- Higher
- Likely range
- Not in the abstract
- Source’s own words
- standardised effect size wake after sleep onset
- Who was studied
- Adult
- Compared with
- placebo or control
- Amount taken
- 1 to 2 g/d
- For how long
- Not in the abstract
- Disagreement between studies
- Not in the abstract
- Kind of record
- Systematic review and meta-analysis
How this rating was reachedstarts at High, 2 steps down: risk of bias and imprecision
- Starts at High
- Risk of bias brought it down to ModerateThe reason for this step is not on record here.
- Imprecision brought it down to LowThe reason for this step is not on record here.
- Ends at Low2 steps down.
- Not written down for this rating
- indirectness and inconsistency
Imprecision stops at the first check that applies; others may apply too.
Published before the signing gate; not yet re-verified.
Randomised trial, 2019
Low certainty, level 2 of 4The serotonin transporter gene-linked polymorphic region (5-HTTLPR) and the sleep-promoting effects of tryptophan: A randomized placebo-controlled crossover study.
van Dalfsen JH, Markus CR. The serotonin transporter gene-linked polymorphic region (5-HTTLPR) and the sleep-promoting effects of tryptophan: A randomized placebo-controlled crossover study. J Psychopharmacol. 2019;33(8):948-954. doi:10.1177/0269881119855978. PMID:31237183.
- Number reported
- -5.188
- Which way it went
- Higher
- Likely range
- Not in the abstract
- Source’s own words
- minutes objective wake-after-sleep-onset regression coefficient
- Who was studied
- Adult
- Compared with
- placebo
- Amount taken
- 1 g/d
- For how long
- Not in the abstract
- Disagreement between studies
- Not in the abstract
- Kind of record
- Randomised controlled trial
How this rating was reachedstarts at High, 2 steps down: risk of bias and imprecision
- Starts at High
- Risk of bias brought it down to ModerateThe reason for this step is not on record here.
- Imprecision brought it down to LowThe reason for this step is not on record here.
- Ends at Low2 steps down.
- Not written down for this rating
- indirectness and inconsistency
Imprecision stops at the first check that applies; others may apply too.
Published before the signing gate; not yet re-verified.
Randomised trial, 1974
Low certainty, level 2 of 4Hypnotic effects of L-tryptophan.
Hartmann E, Cravens J, List S. Hypnotic effects of L-tryptophan. Arch Gen Psychiatry. 1974;31(3):394-397. doi:10.1001/archpsyc.1974.01760150098014. PMID:4370080.
- Number reported
- -50
- Which way it went
- Higher
- Likely range
- Not in the abstract
- Source’s own words
- approximate percent sleep-latency reduction
- Who was studied
- Adult
- Compared with
- placebo or control
- Amount taken
- 1 to 15 g/d
- For how long
- Not in the abstract
- Disagreement between studies
- Not in the abstract
- Kind of record
- Randomised controlled trial
How this rating was reachedstarts at High, 2 steps down: risk of bias and imprecision
- Starts at High
- Risk of bias brought it down to ModerateThe reason for this step is not on record here.
- Imprecision brought it down to LowThe reason for this step is not on record here.
- Ends at Low2 steps down.
- Not written down for this rating
- indirectness and inconsistency
Imprecision stops at the first check that applies; others may apply too.
Published before the signing gate; not yet re-verified.
What is still missing from these readings
- Three give no likely range, so how precise those numbers are is unknown.
- Three do not say how many people took part.
- For how long — Not in the abstract.
Something nobody wrote down is never a zero and never a guess.
L-Tryptophan is not on our to-read list
L-Tryptophan is not on our to-read list, so nothing here is set out to read next for it.
Still to read means nobody here has got to it, not that it was tried and did nothing or that no research exists. A pairing on no list is not a gap: we never set out to read it.
Read next
L-Tryptophan
No other questions read for it
Sleep
28 questions read under it
Sleep
Two other ingredients read against it
Alphabetical, and by nothing else.
This is a library, not advice. No recommendation, no dose, no diagnosis, no ranking. We never ask about your symptoms, and nothing here is tailored to you.