研究发现：早上是最不适宜喝咖啡的时段

    科学研究经常证明，人类的某些根深蒂固的习惯其实是错误的。这一次遭遇挑战的习惯是：在清晨喝咖啡。

    据YouTube科学频道ASAP Science披露，早晨是最不适合喝咖啡的几个时间段之一。原因在于，人体在清晨的皮质醇水平较高。

    皮质醇水平较高时喝咖啡会产生两个问题。首先，咖啡因会干扰身体皮质醇的产生——每当承受压力和出现低血糖时，人体就会释放这种荷尔蒙。喝咖啡导致身体产生的皮质醇减少，更加依赖作为替代物的咖啡因。

    另外一种影响，在习惯早上喝咖啡的人群中较为常见：这种习惯会提高人体对咖啡因的耐受性，因为咖啡因会取代皮质醇自然诱发的能量促进，而不是增添能量。

    我们要记住，2009年的一项研究显示，除了清晨外，人体在三个时间段的皮质醇水平较高。所以喝咖啡或摄入咖啡因的最佳时间是在上午10点至中午，以及下午2点至5点。

    习惯清晨喝咖啡的人应该考虑调整一下时间，以进一步优化咖啡因的摄入。早上醒来第一件事或许是美美地喝上一杯咖啡，但事实证明，这种做法是不管用的。（财富中文网）

    译者：刘进龙/汪皓

    审校：任文科

    Every so often, science disproves the thinking behind a deeply embedded habit we have. The latest: drinking coffee in the morning.

    It turns out, the morning is actually one of the worst times of the day to drink coffee, according to YouTube science channel ASAP Science. The reason? The high levels of cortisol in our bodies early in the morning.

    You see, consuming caffeine when cortisol levels are high creates two problems. One is that caffeine interferes with the body’s production of cortisol, a hormone that’s released in response to stress and low blood glucose. The body ends up producing less cortisol, and relying more on caffeine to compensate.

    The other effect of drinking coffee in the morning is well-known to habitual morning drinkers: It increases the person’s tolerance to caffeine because it replaces the natural cortisol-induced boost instead of adding to it.

    Bear in mind that cortisol levels are high at three times of the day, not just early in the morning, according to a 2009 study. So the best times to drink coffee — or caffeine in general — is between 10 a.m. and noon, and between 2 p.m. and 5 p.m.

    Early morning coffee drinkers should consider adjusting their schedule to better optimize their caffeine intake. As pleasant as a cup o’ joe may be first thing in the morning, turns out it’s quite ineffective.