Tea and coffee is the backbone of the British workforce — but caffeine is a double-edged sword.
It can be the afternoon antidote if you're feeling fatigued and demotivated, but it can also rob you of a quality night's sleep.
In a 2013 study, scientists found people who consumed coffee, tea or energy drinks six hours before bedtime slept for an hour less.
咖啡因定时
咖啡和茶是英国劳动力的支柱，但咖啡因是一把双刃剑。
如果你感到疲劳和缺乏动力，它可能是下午的解药，但它也会剥夺你晚上的优质睡眠。
在2013年的一项研究中，科学家发现，睡前六小时喝咖啡、茶或能量饮料的人睡眠时间少于一小时。
The study was done on 16 'good sleepers', all of whom got six to eight hours sleep a night and typically fell asleep within 30 minutes of getting into bed.
Caffeine makes you more alert by blocking sleep-promoting receptors in your brain called adenosine receptors.
But research in 2015 indicated that caffeine can also delay the timing of your internal body clock.
这项研究是对16名“好睡眠者”进行的，他们每晚睡6到8个小时，通常在上床后30分钟内就睡着了。
咖啡因通过阻断大脑中促进睡眠的腺苷受体使你更加警觉。
但2015年的研究表明，咖啡因也会延迟人体内部生物钟的时间。
Five people were kept under highly controlled conditions for 49 days. Before bedtime, they were given various treatments: either a double-espresso caffeine dose, exposure to bright or dim light, or a placebo. The caffeine delayed their circadian rhythm by 40 minutes.
What many people still don't know is that caffeine can stay in the body for up to 10 hours.
That means people planning on going to bed at 10pm should cut their intake off at 12pm if they want to get the best sleep possible.
5人在49天的高度控制情况中。睡前，他们接受了各种治疗：双倍剂量的浓缩咖啡咖啡因，暴露在明亮或昏暗的光线下，或安慰剂。咖啡因使他们的昼夜节律延迟了40分钟。
许多人仍然不知道的是，咖啡因可以在体内停留长达10个小时。
这意味着计划在晚上10点上床睡觉的人如果想获得最好的睡眠，就应该在中午12点停止摄入。
Caffeine can also make you more tired in other ways.
Once its effect wears off, your body may experience a buildup of adenosine that hits you all at once.
If you're drinking coffee with added sweeteners, they might be adding to your sleep woes. Sweeteners like sugar, syrup, or honey might actually be causing a sugar crash, according to new research.
If your body isn't used to sweeteners in your coffee, it may produce additional insulin as a response. This may cause your blood glucose levels to drop, leading to a good old-fashioned sugar crash.
咖啡因在其他方面也会让你更累。
一旦它的作用消失，你的身体可能会经历腺苷的累积，这会一下子打击你。
如果你喝的是添加了甜味剂的咖啡，它们可能会加重你的睡眠问题。根据一项新的研究，糖、糖浆或蜂蜜等甜味剂实际上可能会导致糖崩溃。
如果你的身体不习惯咖啡中的甜味剂，它可能会产生额外的胰岛素作为反应。这可能会导致你的血糖水平下降，导致老式的血糖崩溃。
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