8. Roasting coffee beans decreases the amount of caffeine
That's why darker roasts generally have lower caffeine levels.
9. Smokers synthesize caffeine more quickly
The same enzyme that breaks down nicotine also breaks down caffeine, so the excess of it allows smokers to metabolize caffeine twice as fast as non-smokers.
10. There is more caffeine in espresso than coffee per milliliter
But since the serving size is so much larger, drip coffee almost always has more caffeine overall than a shot of espresso.
11. Tea leaves have higher caffeine content than coffee beans
But due to the weaker style of brewing, tea is usually much less caffeinated. Tea is also loaded with tannins, a molecular compound that slows the absorption of caffeine.