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  3. Late-Night Drinking Coffee lovers beware. Having a quick" pick-me-up" cup of coffee late in the day will play havoc with you

Late-Night Drinking Coffee lovers beware. Having a quick" pick-me-up" cup of coffee late in the day will play havoc with you

admin2016-07-17  26
问题                         Late-Night Drinking
    Coffee lovers beware. Having a quick" pick-me-up" cup of coffee late in the day will play havoc with your sleep. As well as being a stimulant, caffeine interrupts the flow of melatonin, the brain hormone that sends people into a sleep.
    Melatonin levels normally start to rise about two hours before bedtime. Levels then peak between 2 am and 4 am, before falling again. "It’s the neurohormone that controls our sleep tells our body when to sleep and when to wake, " says Maurice Ohayon of the Stanford Sleep Epidemiology Research Center at Stanford University in California. But researchers in Israel have found that caf-feinated coffee halves the body’s levels of this sleep hormone.
    Lotan Shilo and a team at the Sapir Medical Center in Tel Aviv University found that six volunteers slept less well after a cup of caffeinated coffee than after drinking the same amount of decaf. On average, subjects slept 336 minutes per night after drinking caffeinated coffee, compared with 415 minutes after decaf. They also took half an hour to drop off—twice as long as usual—and jigged around in bed twice as much.
    In the second phase of the experiment, the researchers woke the volunteers every three hours and asked them to give a urine sample. Shilo measured concentrations of a breakdown product of melatonin. The results suggest that melatonin concentrations in caffeine drinkers were half those in decaf drinkers. In a paper accepted for publication in Sleep Medicine, the researchers suggest that caffeine blocks production of the enzyme that drives melatonin production.
    Because it can take many hours to eliminate caffeine from the body, Ohayon recommends that coffee lovers switch to decaf after lunch.
What does paragraph 3 mainly talk about?
选项 A、Different effects of caffeinated coffee and decaf on sleep.
B、Different findings of Lotan Shilo and a team about caffeine.
C、The fact that the subjects slept 415 minutes per night after drinking decaf.
D、The proof that the subjects took half an hour to fall asleep.
答案A
解析 第三段涉及的是一个实验，这个实验的目的是测试含咖啡因咖啡和脱咖啡因咖啡对睡眠的影响，该段主要谈论的是这个实验的结果。
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本试题收录于： 职称英语理工类C级题库职称英语分类
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