For many of us, it is the rocket fuel that gets us going first thing in the morning.

對我們許多人來說，早起第一件事就喝咖啡則如同火箭燃料一般，能讓我們清醒起來動起來。

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.

但是有專家認為，要想獲得咖啡因的最佳效果還得再等上些許時間。因為在上午9：30-11：30這個時間段喝咖啡才是最有效的。

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 hormone cortisol are low because caffeine interacts with the hormone.

馬里蘭州健康科學統(tǒng)一服務大學的神經學家史蒂芬·米勒認為，最好在身體中的荷爾蒙皮質醇水平偏低時喝咖啡，因為這時咖啡因和荷爾蒙相互作用。

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.

他解釋道，當人們在上午8-9點中皮質醇水平較高時喝咖啡，身體對咖啡因有耐受性，并不是很有效。

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.

據《每日電訊報》報道，皮質醇控制人體生物鐘，讓人們感覺很清醒。人體內的激素水平在剛剛睡醒后通常較高，但大約一小時后便開始下降。

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.

米勒先生認為，正是因為這種皮質醇水平下降，人們從咖啡中所含的咖啡因獲得了最大益處——因可以振奮精神，在皮質醇激素下降時刺激皮質醇產生，而且人體對咖啡因的吸收不會受到皮質醇的抵制。

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.

他解釋道，皮質醇水平在中午以及下午5：30-6：30之間達到峰值，這也就意味著這兩個時間段也不是喝咖啡的最佳時間。

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.

他在博客中寫道：“如果當我們的皮質醇濃度在血液中達到高峰時喝了咖啡，那么你可能不應該在這個時候喝咖啡了。

‘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.

“這是因為皮質醇激素的生產與人的警醒度緊密相關，在一天24小時的生物鐘里，早上8-9點皮質醇達到頂峰。”

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.

他補充道，人們早起第一件事就是喝咖啡，他們的皮質醇水平自然就高了，很快他們就會發(fā)現自己需要喝咖啡來達到所需的效果。

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.

不過，他確實贊同每個人在一天中的不同時間段所接受的皮質醇水平因人而異這個說法，即每天喝咖啡的最佳時間也因人而異。

For example, people who get up very early may find their cortisol levels drop earlier than those of people who get up late.

例如，起的很早的人可能會發(fā)現他們的皮質醇水平比那些起的晚的人的皮質醇水平下降的早。

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.

他說，這有助于利用體內細胞把能量轉化成糖，并且對控制人體生物鐘也起作用。