Caffeine is a fascinating drug, one that many of us enjoy via coffee, tea and other products. This video from the American Chemical Society is a quick look on how caffeine actually affects our bodies and how much is a safe dose.
In short, caffeine blocks adenosine receptors in our brains, which makes us groggy and want to sleep. Besides heightening brain activity, increasing heart rate and helping us concentrate, caffeine can also fuel muscle activity (a cup of coffee before exercise can give you a great motivational boost too).
Although the effects of caffeine vary from person to person — and much about caffeine is still being discovered and discussed — the video also points out that 400mg (about three cups of coffee or seven cups of tea) is the recommended safe dose for healthy adults, according to this study. Again, these are just general guidelines that might help you figure out how much coffee is enough for you. 75 cups of coffee, however, is much too much.
While you're at it, you can also time your coffee fix better for maximum impact.