Sleep Better

Lesson 5: Caffeine, alcohol, food, water and exercise

Goal: time what you eat, drink and do so it helps sleep rather than quietly sabotaging it.

Caffeine: earlier than you think

Caffeine blocks the sleep-pressure signal (adenosine) rather than removing it. On average about half of it is still in your body 5 hours later, and in some people the half-life is much longer (anywhere from about 2 to 12 hours, depending on genetics, age, pregnancy, some medications and the contraceptive pill).

In a 2013 study, a large dose of caffeine taken 6 hours before bed still cut total sleep by more than an hour, measured objectively, yet the participants didn’t notice. That’s why “coffee doesn’t affect me” is often wrong.

• Stop caffeine at least 6 hours before bed, and earlier if you’re sensitive or sleeping badly. For a 10:30 pm bedtime that means nothing after about 4 pm; many people do better with a midday cut-off.
• Count everything: coffee, tea (including green), cola, energy drinks, pre-workout powders, chocolate and some cold and flu tablets.

Alcohol: a false friend

Alcohol makes you sleepy and can help you fall asleep faster, which is why people use it as a nightcap. But as your body processes it, sleep in the second half of the night becomes lighter and more broken, and REM sleep is delayed and reduced. You wake more, often early, and feel less refreshed. Alcohol also relaxes the throat muscles, making snoring and sleep apnoea worse.

If you drink, have it earlier in the evening with food, and leave at least 3 hours before bed.

Food

• Avoid large or heavy meals in the last 2 to 3 hours before bed; digestion and reflux can keep you up.
• Going to bed hungry isn’t good either. If you need something, a small, light snack is fine.
• Spicy and fatty food late in the evening is a common trigger for heartburn.

Water: front-load it

How much you drink matters less for sleep than when you drink it.

• Drink plenty in the morning. Huberman suggests about half a litre to a litre of water soon after waking. It helps with morning grogginess, and getting most of your fluids in early makes it easier to ease off at night.
• Some people add a small pinch of salt (or an electrolyte drink) to their morning water, another Huberman habit. It may help you feel more awake if you wake up a bit dehydrated. The evidence for sleep is limited, and if you have high blood pressure, heart or kidney problems, or are on a low-salt diet, check with your doctor first.
• Taper off in the evening. Cut back on drinks in the last 2 to 3 hours before bed so you’re not woken by a full bladder (more on this in Lesson 9). Don’t cut fluids overall; just shift them earlier.

Nicotine

Nicotine is a stimulant. Smoking or vaping in the evening makes it harder to fall asleep, and withdrawal overnight can wake you.

Exercise

Regular physical activity is one of the most reliable ways to sleep better. As for timing, a 2019 review of 23 studies found that evening exercise generally does not harm sleep and may even help. The exception was vigorous exercise finishing within an hour of bedtime, which could delay sleep.

• Move every day, ideally outdoors in daylight (a double win with Lesson 4).
• Keep hard sessions at least an hour or two before bed. Gentle stretching or yoga in the evening is fine.

A simple countdown

All of this fits a popular rule of thumb called 10-3-2-1-0, counting back from bedtime: no caffeine 10 hours before bed, no food or alcohol 3 hours before, no work 2 hours before, no screens 1 hour before, and 0 presses of the snooze button. It hasn’t been tested as a package, but each part is backed by the evidence in this course. Lesson 7 turns it into an evening plan.

Watch

• The science of food, hormones, and sleep (Dr Uma Naidoo, nutritional psychiatrist)
• Eat these foods to stop anxiety, depression and insomnia (Dr Uma Naidoo)

Exercise 5

Write down the time of your last caffeine and your last alcoholic drink for three days. Then work out how many hours before bed each one was. Anything under 6 hours for caffeine or 3 hours for alcohol is the first thing to move.

Sources

• Drake et al. (2013), Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed, Journal of Clinical Sleep Medicine
• Sleep Foundation, How long does it take for caffeine to wear off?
• Ebrahim et al. (2013), Alcohol and sleep I: effects on normal sleep, Alcoholism: Clinical and Experimental Research
• Stutz, Eiholzer & Spengler (2019), Effects of evening exercise on sleep in healthy participants, Sports Medicine
• Centers for Disease Control and Prevention, About sleep
• The Diary of a CEO, Andrew Huberman: My Exact Routine To Optimize Brain & Body (podcast, September 2026)

This course is general information, not medical advice. If you have ongoing sleep problems, loud snoring with pauses or gasping, or sleepiness that affects driving or work, see your doctor. In Australia, if you are struggling or feel unsafe, call Lifeline on 13 11 14.