Coffee is actually a seed which is plucked from the berry of the Coffea plant. It is then grown, dried and roasted, into what we can buy in the supermarket.
Coffee contains caffeine, as most people know but what a lot of people don't know is that caffeine is actually classed as a drug because of the way it stimulates the central nervous system or CNS.
It blocks the sleep chemical adenosine and activates the 'fight or flight' hormone epinephrine, more commonly known as adrenaline.
This means that your neurons fire quicker which leads to that buzzed or on edge feeling you get when you drink it.
In moderation coffee is beneficial. It has a high level of antioxidants, can improve vascular function, boost your mood and may even prevent pernicious diseases such as Parkinsons and Alzheimer's.
On the flip side however, if you drink too much, eg. 4+ cups a day, you run the risk of encountering the downsides. These include an increase in cortisol (the stress hormone), an imbalance in your serotonin levels (which regulates sleep) and an elevation of the heart rate, which is linked to anxiety.
My rules are...
No caffeine after 7pm.
No more than 3 cups a day to avoid developing a dependancy.
One before training can help you to focus.
Grind your own if you're feeling fancy to avoid excess sugar.