第二篇Late-night Drinking Coffee lovers, be careful. Having a quick"pick-me-up"
第二篇 Late-night Drinking
Coffee lovers, be careful. Having a quick"pick-me-up" cup of coffee late in the day will interrupt your sleep.As well as being a stimulant(剂 ), caffeine interrupts the flow of melatonin(褪黑激素) ,the brain hormone that sends people into a sleep.
Melatonin levels normally start to riseabout two hours before bedtime. Levels then peak between 2 am and 4 am, before falling again. "It's theneurohormone (神经激素) thatcontrols our sleep and tells our body when to sleep and when to wake,"says Maurice Ohayon of the Stanford Sleep Epidemi-ology Research Centerat Stanford University in California. But researchers inIsraelhavefound thatcaffeinated coffee halves the body's levels of this sleep hormone.
Lotan Shilo and a team at the SapirMedical Center in Tel Aviv University found that six volun-teers slept less well after a cup of caffeinated coffeethan after drinking the same amount of decaf (脱咖啡因咖啡). On average, subjects slept 336 minutes per night after drinkingcaffeinated coffee, com-pared with 415 minutes after decaf. They also took halfan hour to drop off, twice as long as usual
In the second phase of the experiment,the researchers woke the volunteers every three hours andasked them to give aurine (尿) sample. Shilo measured concentrations of abreakdown product of me-latonin. The results suggest that melatoninconcentrations in caffeine drinkers were half those in decafdrinkers. In apaper accepted for publication in Sleep Medicine, the researchers suggest thatcaffeineblocks production of the enzyme(酶)that drives melatonin production.
Because it can take many hours toeliminate caffeine from the body. Ohayon recommends that cof-fee lovers switchto decaf after lunch.
The author mentions"pick-me-up" to indicate that
A.melatonin levels need to be raised.
B.coffee is a stimulant.
C.neurohormone can wake us up.
D.caffeine can balance our brain hormone.