With its stimulating effects, it's easy to understand why coffee is the second most traded commodity on Earth after oil. For many, it keeps us awake and moving through our busy days.
But how does it work? What exactly does coffee do to your brain? Whenever you're awake, a chemical called adenosine slowly accumulates in your brain. And this adenosine binds to receptors which slow down brain activity-ultimately, the more adenosine there is, the more tired your brain feels. Which makes sense, as the longer you're awake, the more fatigued you become.
Conversely, while you sleep, the concentration of adenosine declines, gradually promoting wakefulness. But it turns out that the caffeine in your coffee is incredibly similar to adenosine in structure. The caffeine works its way through your bloodstream and into the brain where it starts to compete and binds with adenosine receptors.
相反 当你睡眠时 腺甘酸的浓度下降，逐渐使你清醒。不过 咖啡中的咖啡因在结构上和腺甘酸很相似。咖啡因随着血液流动 进入大脑，它在此参与竞争 与腺甘酸受体结合。
But because it's not adenosine, the "sleepiness" effect isn't felt. Adenosine can no longer bind, meaning its calming properties are diminished which is great for you when you're feeling tired! However, with long term use of caffeine, your brain responds by creating more adenosine receptors-which means more caffeine is required to elicit the same response.
It also means that when you try to quit drinking coffee or miss your daily intake. You might experience some withdrawal symptoms and feel more tired than you would have before you ever drank coffee! But the caffeine doesn't stop there! It also stimulates the production of adrenaline--you know, the Fight or Flight hormone? This increases your heart rate, gets your blood pumping and even opens up your airways.
这也说明, 当你想戒除咖啡或忘记喝时，就可能会经历某些断瘾症状，感觉比未开始喝咖啡前疲倦的多，不过 咖啡因的作用不止于此！它也会促进肾上腺素分泌，对 就是“或打或逃“的荷尔蒙？它可导致心跳加速 血流加快，甚至使导气管扩张。
Furthermore, it affects Dopamine levels by preventing its reabsorption in the brain which makes you feel happy! In fact, this is the exact same thing that cocaine does, just to a lesser degree. It's a drug, after all! This dopamine stimulation is also the aspect of coffee that makes it moderately addictive.
So can you drink too much coffee? It turns out there is a lethal dose of caffeine which is somewhere around 150mg of caffeine per kilogram of your body. This means if you weigh 70kg you would require 14,000mg of caffeine to overdose. Put into perspective an average cup of coffee contains roughly 150mg of caffeine, meaning if you are 70kg, approximately 70 cups of coffee would kill you. However, you'd have to drink those cups all at once making it effectively impossible to overdose on caffeine from coffee, since you wouldn't be able to physically fit that much in your stomach.
那么 喝咖啡可能过量吗？其实 咖啡因存在致死剂量，大约为每千克体重150毫克咖啡因。也就是说 如果你体重70千克 则需要14克咖啡因才会过量。形象点说 平均每杯咖啡含量有150毫克咖啡因。若你的体重为70千克 喝下70杯咖啡会致死。但是 你得一次喝下这么多咖啡，单单喝咖啡导致咖啡因过量几乎不可能，因为你根本无法将这么多东西装进胃里。
You'd also start experiencing mania and hallucinations before getting to this point. Caffeine also has a halflife of around 6 hours-so if you drank a standard coffee with around 150mg of caffeine, after about 6 hours there will only be 75mg left in your system and you'll be feeling half of the effect.
And 6 hours after that, you'll have 37.5mg-Leaving more room for adenosine to jump back into action which is why you may reach for another cup throughout the day to maintain that glorious, alert and energetic feeling.
So drink up! And enjoy the buzz while it lasts:)