Caffeine is the world's most widely used stimulant, and for most people a moderate amount is fine. But it can disturb sleep long after the buzz has worn off.
How it works
Caffeine blocks adenosine, a chemical that builds up during the day and makes you sleepy. It typically peaks in your blood within an hour, and for many adults its half-life is around five to six hours. That means half of the caffeine from a mid-afternoon coffee could still be in your system at bedtime.
How much is too much?
Health authorities such as the U.S. FDA say up to about 400 mg a day, roughly four cups of brewed coffee, is not generally associated with negative effects in most healthy adults. Sensitivity varies a lot, and pregnant women are usually advised to keep to around 200 mg.
Hidden sources
- Tea, including green tea.
- Energy drinks and cola.
- Chocolate, especially dark.
- Some painkillers and pre-workout supplements.
Tips
- Set a caffeine cut-off about 8 hours before bedtime.
- Switch to decaf or herbal tea in the afternoon.
- Reduce gradually to avoid withdrawal headaches.
- Notice how you sleep after days with less caffeine.
General information only, not medical advice. Always talk to a qualified health professional about your own situation.
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