Late-night Drinking Coffee lovers, be careful. Having a quick "pick-me-up" cup of coffee late in the day will interrupt your

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问题                         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(兴奋剂), caffeine interrupts the flow of melatonin(褪黑激素), the brain hormone that sends people into a sleep.
    Melatonin levels normally start to rise about two hours before bedtime. Levels then peak between 2 am and 4 am, before falling again. "It’s the neurohormone(神经激素)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(脱咖啡因咖啡). 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.
    In the second phase of the experiment, the researchers woke the volunteers every three hours and asked them to give a urine(尿)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(酶)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.
Ohayon advises coffee lovers

选项 A、to drink less coffee during the day.
B、to take decaf after lunch.
C、not to go to bed after taking coffee.
D、not to drink coffee after supper.

答案B

解析 题意:奥哈永建议咖啡爱好者午餐之后喝低咖啡因的咖啡。短文最后一段提到“因为将咖啡因从体内排除需要几个小时的时间,奥哈永建议咖啡爱好者午餐之后就改换成低咖啡因咖啡”,故选B。
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