Why the worst time to drink coffee is actually in the morning

Our bodies produce a hormone called cortisol, which has been branded the "stress hormone," because it tends to appear when we are either stressed or fearful. But that same hormone is also a key component of our natural, day-long hormonal cycle, known as the circadian clock, which helps wake us up in the morning and wind us down at night. The gist is that when our body releases cortisol, we feel more awake.

我们的身体会产生一种叫做皮质醇的激素，通常被称为“应激激素”，因为当我们感到压力或恐惧时，这种激素就会产生。还有一种激素，是我们人体每天荷尔蒙周期的重要组成部分，即生物钟，每天在早晨提醒我们起床，晚上催促我们睡觉。最关键的是我们的身体释放皮质醇时，我们会更清醒。

As the above video, which was put together by the popular science explainer Youtube channel ASAP Science, shows, there is such thing as a less than ideal time to drink coffee. And that time is first thing in the morning, when cortisol levels are highest.

根据Youtube 尽快科学（ASAP Science）栏目的著名科学解说员收集的视频显示，一天当中存在不适宜喝咖啡的时间，即早晨一起来就喝咖啡，因为那时皮质醇指数最高。

There are two basic problems with consuming caffeine when cortisol production is high. First, caffeine tends to interfere with the production of cortisol. The body then produces less of the hormone and relies more on the caffeine.

在皮质醇达到最高时摄取咖啡因，会造成两个问题。首先，咖啡因会妨碍皮质醇的产生。皮质醇水平下降，会使人体更加依赖咖啡因。

Second, drinking coffee while cortisol is high leads us to develop long-term tolerances for caffeine, which is why so many habitual coffee drinkers say it has less of an effect on them. In effect, caffeine replaces the boost we would ordinarily get from cortisol rather than supplementing it.

第二，这时饮用咖啡，会使人体长期适应咖啡因，这也是为什么很多咖啡饮用者说咖啡对他们没有丝毫影响。事实上，咖啡因不是补充体力，而是会取代我们本应从皮质醇获得的动力。

Three times throughout the day—in the early morning, around mid-day, and in the evening–cortisol levels rise. It’s highest between 6 a.m. and 10 a.m. (particularly so between 8 a.m. and 9 a.m.).

一天中三个时间段——清早、正午和晚上，皮质醇会升高。早上六点和十点之间达到最高（尤其是八九点时）。

It’s during the troughs above — between roughly 10 a.m. and noon, and 2 p.m. and 5 p.m.—when people should drink coffee if they want to get the most out of their caffeine. Between those hours, the coffee is actually most needed, and, perhaps most importantly, will not interfere with our body’s own essential mechanism for keeping us alert.

在皮质醇指数达到最低时——大约十点到正午，下午两点到五点——人们可以饮用咖啡，这时可以很好的利用咖啡因来提精。这段时间内，人们才真正需要喝咖啡，最重要的是，不会干扰到人体自身使我们保持清醒的内在机理。

Studies have shown that when people talk about developing a "tolerance" for coffee, they are often talking—albeit unknowingly—about the reality that their coffee consumption has fostered a decrease in the amount of cortisol their body produces during the day.

研究显示，人们经常所说的对咖啡“免疫”，其实是指咖啡的摄入使每天人体内产生的皮质醇数量降低。

Coffee drinkers who are exhausted in the morning without their coffee have likely altered their circadian rhythm in such a way that they need the caffeine boost in order to reach the level of wakefulness they used to achieve without it.

那些早上不喝咖啡就会感觉困乏的人，已经改变了他们的生理节律，不得不借助咖啡因达到之前不用喝咖啡就能很精神的状态。

Maybe it’s time to reconsider when you drink your first cup.

是时候想想什么时候才是喝第一杯咖啡的正确时间。

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来源:华盛顿邮报爱语吧作者:刘瑞洁