What you put in your body, and when, quietly makes or breaks the night. Three things matter most — caffeine, alcohol, and late food — and the timing matters more than most people think.
Caffeine has a half-life of about 5–6 hours, so an afternoon coffee is still half-active at bedtime; a controlled study found caffeine taken even 6 hours before bed measurably cut sleep. Practical rule: none within ~8–10 hours of sleep (for many, a cut-off around early afternoon). It works by blocking adenosine — the 'sleep pressure' that should build all day — so late caffeine steals from the very drive that puts you under. Evidence ●●●●○
Alcohol helps you fall asleep and then wrecks the second half of the night: it fragments sleep, suppresses REM, and worsens snoring and apnea. A nightcap is one of the most reliable ways to feel unrested despite technically 'sleeping.' If you drink, leave several hours before bed and keep it moderate. Evidence ●●●●○
A large meal close to bedtime raises core temperature, spikes glucose, and can cause reflux — all working against sleep. Aim to finish eating about 3 hours before bed (though don't go to bed starving either — a small, boring snack is fine). Nicotine, like caffeine, is a stimulant best kept out of the evening. Evidence ●●●○○
The simplest wins
Last coffee by early afternoon, last drink well before bed, last big meal ~3 hours before. None of these costs a penny, and together they fix more bad nights than any supplement.
The Sleep Guide