Topic

Sleep

How long people slept, how quickly they fell asleep and how they rated it.

This page is not a ranking. Ingredients appear in order of how much we have read here.

The 11 things measured here · ingredients read against each

Read here so far: 28 questions across 11 ingredients

Melatonin

Melatonin and SleepThree sources, all measured higherModerate certainty, level 3 of 4
Melatonin and Total sleep timeTwo sources, all measured higherLow certainty, level 2 of 4
Melatonin and Sleep efficiencyOne source, found no clear differenceModerate certainty, level 3 of 4
Melatonin and Circadian phase (dim light melatonin onset, DLMO)One source, measured lowerLow certainty, level 2 of 4
Melatonin and Sleep onset latencyOne source, measured lowerLow certainty, level 2 of 4
Melatonin and Sleep quality (subjective)One source, measured higherLow certainty, level 2 of 4

Caffeine

Caffeine and Sleep efficiencyTwo sources, all measured lowerModerate certainty, level 3 of 4
Caffeine and Total sleep timeTwo sources, saying different thingsModerate certainty, level 3 of 4
Caffeine and Sleep onset latencyOne source, measured higherLow certainty, level 2 of 4
Caffeine and Deep (slow-wave) sleepOne source, measured lowerVery low certainty, level 1 of 4
Caffeine and REM sleepOne source, found no clear differenceVery low certainty, level 1 of 4

Ashwagandha

Ashwagandha and Sleep onset latencyOne source, measured lowerLow certainty, level 2 of 4
Ashwagandha and Total sleep timeOne source, measured higherLow certainty, level 2 of 4
Ashwagandha and Wake after sleep onset (WASO)One source, measured lowerLow certainty, level 2 of 4
Ashwagandha and Sleep quality (subjective)One source, measured lowerVery low certainty, level 1 of 4

L-theanine

L-theanine and Pittsburgh Sleep Quality Index (PSQI)One source, measured lowerLow certainty, level 2 of 4
L-theanine and Sleep efficiencyOne source, measured higherLow certainty, level 2 of 4
L-theanine and Sleep quality (subjective)One source, measured higherLow certainty, level 2 of 4
L-theanine and Sleep onset latencyOne source, measured lowerVery low certainty, level 1 of 4

Magnesium

Magnesium and Sleep onset latencyOne source, measured lower, and one source carries a noticeLow certainty, level 2 of 4
Magnesium and Total sleep timeOne source, measured higher, and one source carries a noticeLow certainty, level 2 of 4

Potassium

Potassium and Sleep efficiencyOne source, measured higherVery low certainty, level 1 of 4
Potassium and Wake after sleep onset (WASO)One source, measured lowerVery low certainty, level 1 of 4

5-HTP

5-HTP and Pittsburgh Sleep Quality Index (PSQI)One source, measured lowerLow certainty, level 2 of 4

Glycine

Glycine and Sleep quality (subjective)One source, measured higherModerate certainty, level 3 of 4

Iron

Iron and Restless Legs Syndrome SeverityOne source, measured lower, and one source carries a noticeLow certainty, level 2 of 4

L-Tryptophan

L-Tryptophan and SleepThree sources, all measured higherLow certainty, level 2 of 4

Magnesium Glycinate

Magnesium Glycinate and SleepThree sources, all measured higher, and one source carries a noticeVery low certainty, level 1 of 4

Where the sources say different things

Every side in full, because one line would have to pick one of them.

Each bar is one source’s range, drawn against the line of no difference: left of the line is lower, right is higher. Widths are not comparable between rows.

Caffeine and total sleep time
Two sources here, and they say different things: one measured lower total sleep time and one found no clear difference.
Moderate certainty, level 3 of 4The sources say different things
One source’s range, crossing no difference: these numbers fit no effect too. The sources here say different things. Systematic review, 2025

How much of this is one source

Read from 22 sources. 22 of the 28 questions here rest on a single source with nothing yet to check them against, and on 1 question the sources say different things.

What is still to read is kept per ingredient, not per topic, so every ingredient named above carries its own list.

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.

The other 14 topics

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.