Coffee & your body
Coffee and your body: what the science says
What happens in your brain, nerves, stomach and gut after a cup, how your liver enzymes break caffeine down, how much is too much and when to drink it. Every claim links to the study behind it.
Guides
Coffee & your bodyWhat Coffee Does to Your Body: A Joyful Minute-by-Minute TourCaffeine is absorbed almost completely and peaks in your blood within about 30 to 60 minutes.
Coffee & your bodyHow Caffeine Works: The Friendly Science of Your Morning LiftCaffeine works mainly by blocking adenosine receptors in the brain.
Coffee & your bodyWhy Does Coffee Make You Poop? A Joyful Tour of Coffee and DigestionWhy does coffee make you poop? It switches on muscle activity in the colon, in some people within about 4 minutes of drinking.
Coffee & your bodyCaffeine Metabolism: How CYP1A2 Decides How Long Your Coffee LastsCaffeine metabolism happens mainly in the liver, where the enzyme CYP1A2 handles about 95% of caffeine, turning most of it into paraxanthine.
Coffee & your bodyIs Coffee Good for You? A Friendly, Evidence-Based Look at the Benefits and RisksFor most healthy adults, yes: moderate coffee drinking (about 3-4 cups a day) is linked with lower risk of early death, type 2 diabetes, liver disease and heart disease in large observational studies.
Coffee & your bodyHow Much Caffeine Is Too Much? Safe Limits, Cup by CupFor healthy adults, EFSA considers up to 400 mg of caffeine a day and single doses up to 200 mg to raise no safety concerns; 400 mg is roughly four 8-oz cups of brewed coffee, and individual tolerance may be lower.
Coffee & your bodyHow Long Does Caffeine Stay in Your System? Your Coffee Clock ExplainedCaffeine peaks in your blood about 30-60 minutes after a coffee and has an average half-life of about 4-5 hours, ranging from roughly 3 to 10 hours between healthy adults.
Coffee & your bodyThe Best Time to Drink Coffee: Your Happy, Sleep-Friendly Coffee DayThe best time to drink coffee for most people is morning to early afternoon, with the last caffeinated cup at least about 9 hours before bed to protect sleep.
Coffee & your bodyCoffee and Blood Pressure: A Calm Look at Coffee and Heart HealthCoffee raises blood pressure for a few hours, most in people who rarely drink it or have hypertension, but daily drinkers develop near-complete tolerance within days.
Coffee & your bodyCoffee and Acid Reflux: Keep Your Cup and Calm the BurnCoffee and acid reflux are linked mostly at the level of symptoms: coffee stimulates stomach acid and can trigger heartburn in sensitive people.Coffee and your body: a practical guide
Coffee is one of the most studied drinks in the world. Large reviews link moderate coffee drinking with several good outcomes, but most of that evidence is observational, so it shows associations, not cause and effect. Coffee is a pleasure, not a medicine. Here is how to enjoy it in a way that suits your body.
How caffeine works and how long it lasts
Caffeine is absorbed quickly and works mainly by blocking adenosine receptors, the signals that build up sleep pressure during the day. How caffeine works explains the brain side. Your liver enzyme CYP1A2 breaks down about 95% of it, and the typical half-life is about 4 to 5 hours, though it varies widely between people. Read how long caffeine stays in your system and caffeine metabolism and CYP1A2 for the details.
How much and when
- EFSA considers up to 400 mg of caffeine a day safe for healthy adults, and up to 200 mg a day in pregnancy and while breastfeeding.
- A meta-analysis of 24 studies suggests finishing a regular coffee at least 8.8 hours before bed to protect sleep.
- People with heart rhythm problems, anxiety or panic disorder, or who take medicines that interact with caffeine may need less. Ask your doctor or pharmacist.
More in how much caffeine is too much and the best time to drink coffee.
Plan your own coffee day
The caffeine planner draws your caffeine curve from your drinks, wake time and bedtime, adjusts for factors that change caffeine half-life, and suggests a last-cup time. It is an educational model, not medical advice.
Frequently asked questions
Is coffee good for you?
For most healthy adults, moderate coffee drinking is linked with several good outcomes in large reviews, including lower risk of type 2 diabetes and liver disease. Most of this evidence is observational, so it cannot prove cause and effect. Pregnancy, heart rhythm problems and some medicines call for more care, so check with your doctor.
How many cups of coffee a day is safe?
EFSA considers up to 400 mg of caffeine a day safe for healthy adults. An 8 oz cup of filter coffee has about 95 mg, but real cups vary widely, so 400 mg is roughly four regular 8 oz cups, or fewer large mugs. In pregnancy the guide is up to 200 mg a day. This is general information, not medical advice.
Why does caffeine affect people differently?
Mostly because people clear it at different speeds. The liver enzyme CYP1A2 handles about 95% of caffeine, and its activity depends on genes, smoking, hormones, pregnancy and some medicines. In one study of healthy young men, the half-life ranged from 2.7 to 9.9 hours. Sensitivity in the brain also differs between people.