Reviewed
Reviewed on 2026-09-19 against the evidence rules: every claim carries a grade, every claim and every safety flag carries a source, and every citation was re-resolved against the record it names. The read was delegated by the owner on 2026-09-18 and signed by the Lead on his behalf (D-295) — it is a delegated review, not the owner's own reading of the page. Every claim on it carries an evidence grade and a named weakest link. It is educational and is not medical advice.
Last reviewed
Two dietary decisions have measured effects on sleep: the last caffeine and the last meal. Both make it worse. Nothing cited in this section makes it better, and the entry says so rather than filling the gap.
Safety
Adverse effects
Moving the last coffee earlier can produce caffeine withdrawal: headache in about half of experimental cases, beginning 12 to 24 hours after the last dose and lasting two to nine days. Expect that week; do not read it as a result.
No data in your group
The late-eating finding rests on 52 people measured at a single point. It is the weakest study cited in this section and is included because the alternative — leaving the question out — would read as if nothing were known.
What the evidence says, and how strong it is
A grade belongs to one claim, in one population, for one preparation — never to a compound, a food or a page. Open a grade to see the four links between the evidence and the thing you would actually do, and which of them is doing the least work.
A randomised trial found that caffeine taken six hours before bed still disrupted measured sleep — not only the dose at bedtime, and not only the one three hours before.
Evidence grade B: May supportIn whom: Adults sleeping at home at their habitual bedtimes
What form: 400 mg of caffeine six hours before bed
Measured as: Objectively measured sleep disruption the same night
Why this grade
- Weakest link
- Study quality — design, size, blinding or replication. One randomised trial supports the six-hour figure, and nobody has repeated it at that timing.
- What was actually studied
- Adults sleeping at home at habitual bedtimes, given 400 mg caffeine
- Detail worth knowing
- Concludes that caffeine taken 6 hours before bedtime has important disruptive effects on sleep, supporting advice to avoid substantial caffeine for a minimum of 6 hours before sleep.
In a cross-sectional study of 52 healthy volunteers, eating during the nocturnal period correlated with poorer sleep quality. Fifty-two people, measured once: it cannot say which way the arrow points.
Evidence grade C: Early research suggestsIn whom: 52 healthy volunteers
What form: Food eaten during the night-time period
Measured as: Self-reported sleep quality
Why this grade
- Weakest link
- Study quality — design, size, blinding or replication. Fifty-two people measured once cannot say which way the arrow points: people who sleep badly may simply be the people awake to eat.
- What was actually studied
- 52 healthy volunteers (27 women, 25 men) — cross-sectional, not followed over time (n = 52)
- Detail worth knowing
- Food intake during the nocturnal period correlated with poorer sleep quality. Cross-sectional and small: it cannot say which way the arrow points, and is recorded here as `cohort` only because the contract's design vocabulary has no cross-sectional value.
None of the sources cited across this section identifies a food or drink that improves measured sleep. Every sleep finding here is a cost. The absence is published rather than filled.
Evidence grade D: Human evidence insufficientIn whom: Healthy adults
What form: Any food or drink cited anywhere in these Brain Diet entries
Measured as: Any improvement in measured sleep
Evidence does not support
Why this grade
- Weakest link
- Outcome — what was measured is not what you would notice. None of these sources set out to find a food or drink that improves measured sleep, so this is an absence in a literature that was not looking rather than a tested negative.
- What was actually studied
- Adults sleeping at home at habitual bedtimes, given 400 mg caffeine; 52 healthy volunteers (27 women, 25 men) — cross-sectional, not followed over time (n = 52)
- Detail worth knowing
- Concludes that caffeine taken 6 hours before bedtime has important disruptive effects on sleep, supporting advice to avoid substantial caffeine for a minimum of 6 hours before sleep.
- Food intake during the nocturnal period correlated with poorer sleep quality. Cross-sectional and small: it cannot say which way the arrow points, and is recorded here as `cohort` only because the contract's design vocabulary has no cross-sectional value.
Everything above, and where it comes from
- Drake C, Roehrs T, Shambroom J, Roth T (2013). Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. Journal of Clinical Sleep Medicine 9(11):1195–1200
- Crispim CA, Zimberg IZ, dos Reis BG, Diniz RM, Tufik S, de Mello MT (2011). Relationship between food intake and sleep pattern in healthy individuals. Journal of Clinical Sleep Medicine 7(6):659–664
- Juliano LM, Griffiths RR (2004). A critical review of caffeine withdrawal: empirical validation of symptoms and signs, incidence, severity, and associated features. Psychopharmacology (Berl) 176(1):1–29
The one thing worth doing
Change the clock before you change the food: move the last caffeine to six hours before bed. It is free, and it shows up within a week.