The thing is, everyone tolerates caffeine differently. Some people will have no problem drinking four cups of coffee, about 400 milligrams of caffeine daily, whereas others get jittery after one cup or less. So, if your brain is feeling a bit sluggish, foggy, or flat-out running on empty, what can you do? Well, caffeine may help a bit with alertness, but there’s another ingredient that’s even better for boosting brain energy.*