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

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

admin2012-07-29  84
问题                             Late-night Drinking
    Coffee lovers beware. Having a quick "pick-me-up" cup of coffeel 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 a. m. and 4 a. m. , before falling again. "It’s the neurohormone that controls our sleep and 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 caffeinated 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.
The author of this passage probably agrees that______.
选项 A、coffee lovers sleep less than those who do not drink coffee
B、we should not drink coffee after supper
C、people sleep more soundly at midnight than at 3 a. m.
D、if we feel sleepy at night, we should go to bed immediately
答案B
解析 文章的结尾谈到，“Ohayon建议爱喝咖啡的人午饭后应该换喝脱咖啡因咖啡”。另外，整个文章都在探讨咖啡因影响睡眠的机理，所以，作者大概会同意“晚饭后不应该喝咖啡”的说法。选项A是一个全称判断，这等于说“所有喜欢喝咖啡的人都比不喝咖啡的人睡觉少”。这不一定，因为如果咖啡适量，喝咖啡的时间适当，咖啡不会影响睡眠。所以，作者可能不会同意这种说法。根据文章第二段第二个句子，选项C是错的。根据文章第二段的第一个句子，我们体内褪黑激素(睡眠激素)的深度在我们上床时间前两个小时开始上升，而这个时候我们会开始有困意。反过来说就是，人们并非一有困意就睡觉。所以，选项D不是答案。
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