阅读材料，回答题： Late-Night Drinking Coffee lovers beware. Having aquick" pick-me-up" cup of coffee late in the day will playhavocwith your sleep. As well as being astimulant, caffeine interrupts the flow of melatonin, theB．rain hormone that sends people into asleep. Melatonin levels normally start to rise about two hours before bedtime. Levels then peak be-tween 2 am and 4 am, before failing again. "It&39;s the neurohormone that controls our sleep tells ourB．ody when to sleep and when to wake, "says Maurice Ohayon of the Stanford Sleep EpidemiologyResearch Center at Stanford University in California. but researchers in Israel have found that caf-feinated coffee halves the body&39;s levels of this sleep hormone. Lotan Shilo and ateam at the Sapir Medical Center in Tel Aviv University found that six vol-unteers slept less well after acup of caffeinated coffee than after drinking the same amount of de-caf. On average, subjects slept 336 minutes per night after drinking caffeinated coffee, comparedwith 415 minutes after decaf. They also took half an hour to drop off--twice as long as usual--andjigged around in bed twice as much. In the second phase of the experiment, the researchers woke the volunteers every three hoursand asked them to give aurine sample. Shilo measured concentrations of abreakdown product ofmelatonin. The results suggest that melatonin concentrations in caffeine drinkers were half those indecaf drinkers. In apaper accepted for publication in Sleep Medicine, the researchers suggest thatcaffeine blocks production of the enzyme that drives tnelatonin production. because it can take many hours to eliminate caffeine from the body, Ohayon recommends thatcoffee lovers switch to decaf after lunch. The author mentions" pick-me-up" to indicate that__________. 查看材料