????科學研究經常證明，人類的某些根深蒂固的習慣其實是錯誤的。這一次遭遇挑戰的習慣是：在清晨喝咖啡。

????據YouTube科學頻道ASAP Science披露，早晨是最不適合喝咖啡的幾個時間段之一。原因在于，人體在清晨的皮質醇水平較高。

????皮質醇水平較高時喝咖啡會產生兩個問題。首先，咖啡因會干擾身體皮質醇的產生——每當承受壓力和出現低血糖時，人體就會釋放這種荷爾蒙。喝咖啡導致身體產生的皮質醇減少，更加依賴作為替代物的咖啡因。

????另外一種影響，在習慣早上喝咖啡的人群中較為常見：這種習慣會提高人體對咖啡因的耐受性，因為咖啡因會取代皮質醇自然誘發的能量促進，而不是增添能量。

????我們要記住，2009年的一項研究顯示，除了清晨外，人體在三個時間段的皮質醇水平較高。所以喝咖啡或攝入咖啡因的最佳時間是在上午10點至中午，以及下午2點至5點。

????習慣清晨喝咖啡的人應該考慮調整一下時間，以進一步優化咖啡因的攝入。早上醒來第一件事或許是美美地喝上一杯咖啡，但事實證明，這種做法是不管用的。（財富中文網）

????譯者：劉進龍/汪皓

????審校：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.