Caffeine boosts energy, fights fatigue and steps up your heart rate. The answer is, all may be true. Caffeine acts as a diuretic, and if your only fluid intake is caffeine-based, you may notice you're always thirsty.
Caffeine can also upset some peoples' stomachs.
If you enjoy caffeine, keep intake in balance and try to include plenty of more nutritious beverages, like milk or juice. To cut back on caffeine, start gradually to avoid withdrawal headaches. Mix half decaf and half regular or try every other cup decaf.