研究表明：每天上午10:30喝咖啡最佳时间
Why 10.30am is the ideal time for a coffee: Our body clocks are most receptive to the effects of caffeine a few hours after wakingFor many of us, it is the rocket fuel that gets us going first thing in the morning.
But one expert has argued that to get the maximum effect of caffeine, it's better to hold on a few hours - because coffee is most effective if consumed between 9.30am and 11.30am.
Steven Miller, a neuroscientist from the Uniformed Services University of the Health Sciences in Maryland, says it is best to drink coffee when the body’s levels of the hormonecortisol are low because caffeine interacts with the hormone.
He explained that people who drink coffee when their cortisol levels are high – namely, between 8am and 9am – develop a tolerance to caffeine, meaning it becomes less effective.
Cortisol controls the body clock and causes people to feel wide awake, The Telegraph reports.
The body’s levels of the hormone are usually high just after a person wakes up but start to fall about an hour afterwards.
Mr Miller argues that it is during this drop in cortisol levels that people get the most benefit from the caffeine in coffee – it gives them a boost as it encourages cortisol production when their cortisol levels start to drop and they do not become resistant to its benefits.
He explained that cortisol levels also peak at lunchtime and between 5.30pm and 6.30pm, meaning that these would also not be good times to drink coffee.
Writing on his blog he said: ‘If we are drinking caffeine at a time when your cortisol concentration in the blood is at its peak, you probably should not be drinking it.
‘This is because cortisol production is strongly related to your level of alertness and cortisol peaks for your 24 hour rhythm between 8 and 9am on average.
‘One of the key principles of pharmacology is use a drug when it is needed. Otherwise, we can develop tolerance to a drug administered at the same dose.’
He added that people who drink a coffee first thing in the morning, when their cortisol levels are naturally high, will soon find themselves needing to make their coffee stronger and stronger to get the desired effect.
However, he did accept that cortisol levels at different times of day vary from person to person meaning that the best time of day to drink a coffee also differs between people.
For example, people who get up very early may find their cortisol levels drop earlier than those of people who get up late.
The PhD student explained that cortisol levels in the body vary throughout the day.
He says it helps turn energy into sugar to be utilised by cells in the body and that it also plays a role in controlling the body clock.
很多人早晨起床第一件事就是喝一杯咖啡，解困去乏，补充动力。但专家称，要想发挥咖啡因的最佳作用，最好等到9:30到11:30再喝，因为这个时间段人体内皮质醇含量较低，喝咖啡效果最好。
美国健康科学统一服务大学（Uniformed Services University of the Health Sciences）神经学教授史蒂文?米勒认为，由于咖啡因会与荷尔蒙皮质醇（hormonecortisol）发生反应，而早晨8点到9点之间，皮质醇含量高，会对咖啡因产生抵抗，因此等体内皮质醇含量较低时喝咖啡最好。
皮质醇控制人体的生物钟，可以使人保持敏锐清醒。通常，人每天睡醒之后体内荷尔蒙含量较高，一般一小时之后荷尔蒙含量开始下降。米勒教授表示，当荷尔蒙皮质醇含量下降时，咖啡因开始发挥作用促进皮质醇产生，起到提神的作用。
另外，午餐时间和下午5:30到6:30之间，皮质醇含量达到最高，这两个时间段也不适宜喝咖啡。米勒教授说：“药理学上有一条关键原则，就是要择机施药。时机不对只会适得其反。”在皮质醇含量高的时间段内喝咖啡，需要越来越浓的咖啡才能起到理想的效果。
然而，米勒教授认为，不同人在不同时间段体内皮质醇含量也不同，因此喝咖啡最佳时间也可能因人而异。
(编辑：何莹莹）
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