Sleep quality can decline even for people who avoid coffee after 2 p.m., according to a new study. Caffeine consumed in the morning may still affect sleep at night, prompting advice to manage both the amount and the timing of intake.
Why Long Sleep Doesn't Always Mean Deep Sleep
A study published in a journal of the academic publisher MDPI analyzed 32 earlier studies that used electroencephalography (EEG) and found that people who consumed caffeine tended to sleep more lightly even when they slept more than eight hours, U.S. health outlet Prevention reported. The pattern was especially pronounced in non-REM (NREM) sleep, which is important for physical recovery.
Drinking caffeine immediately after waking is no guarantee of safety either. In earlier research cited by the authors, changes were observed in brain waves at the usual bedtime even when 200 milligrams of caffeine was consumed just 10 minutes after waking.
Caffeine blocks the action of adenosine, which builds up in the brain and induces drowsiness. It works by occupying the receptors that adenosine would otherwise bind to, reducing the sensation of fatigue. But that can also keep the body in a state of arousal when it should be winding down. Caffeine can raise the heart rate and constrict blood vessels in the brain, which can also affect blood pressure.
Avoid Caffeine 8 to 10 Hours Before Bedtime
Rather than setting a uniform cutoff at 2 p.m., it is better to calculate the time to stop caffeine based on when you go to bed. Caffeine typically takes four to 10 hours to break down in the body, but that can vary with an individual's metabolic rate, medications and whether they have eaten. Even someone who stops drinking coffee at 2 p.m. may still see effects on sleep if they go to bed at 9 p.m.
Experts recommended halting caffeine intake at least eight to 10 hours before falling asleep. For someone who goes to bed at 10 p.m., that means avoiding coffee from around noon. Daily intake is recommended to stay below 400 milligrams, and one suggested approach is to have the first coffee about 90 minutes after waking rather than immediately.
Because levels of the stress hormone cortisol rise in the morning, delaying caffeine intake may help reduce reliance on its stimulant effect, according to the explanation. Concerns have also been raised that prolonged high cortisol levels can lead to anxiety, fatigue and brain fog.
Switching to teas with relatively lower caffeine content, such as green tea, is another way to cut coffee consumption. A cup of green tea contains about 29 milligrams of caffeine. L-theanine, an amino acid found in green tea, is known as a compound that can help ease tension and improve concentration.
"Coffee Investing" Instead of Gold
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