If you've ever reached for a cup of coffee to give yourself a boost during a mid-afternoon slump or downed a double cappuccino to stay up late studying, you know the energizing effects of caffeine. But you may also have noticed that those energizing effects don't last forever; later on, you're likely to experience a "crash," wherein your energy fades and your mood falls. While this is probably unpleasant, it's completely normal and even expected.
Caffeine is extremely popular around the world, in part due to its stimulant capabilities. An ingredient in coffee, tea, soft drinks, chocolate, energy drinks and certain pain medications, caffeine is a natural substance but also a stimulant drug, says the National Institutes of Health. Because it acts upon your central nervous system, it produces a number of physiological and emotional effects. For example, caffeine increases your heart rate, promotes wakefulness and alleviates fatigue, sharpens your focus and concentration, according to the University of Maryland Medical Center.
Despite the appealing effects of caffeine, there are some down sides as well. Brown University's Health Services state that caffeine's effects are most pronounced in the first hour after ingestion. And while some effects may still be detected as long as four to six hours after consumption, you may notice a "crash" as the caffeine leaves your system. That's because caffeine initially stimulates your body to produce more adrenaline and dopamine than usual, two substances in your body that contribute to energy and positive mood; when these chemicals begin to drop again, you can experience fading energy and a drop in mood.
Excessive caffeine consumption can cause even more problems. Besides the up-and-down aspects of mood and energy, ingesting too much caffeine can cause jittery feelings, restlessness, irritability, headaches, tremors and insomnia, according to the University of Utah Health Care Center. Consuming a lot of caffeine can also make you tolerant to its effects, such that you need larger and larger doses to experience the increased energy and alertness you usually feel from caffeine.
Dosage and Safety
These points may make you wonder what is a safe level of caffeine intake, and what dose is considered excessive or harmful. While there is no one right answer for everyone, since some people are more sensitive to caffeine than others, the National Sleep Foundation states that there is no evidence that mild to moderate use of caffeine -- roughly 100 to 250 milligrams per day -- is harmful. If you consume a lot of caffeine and are concerned about energy and mood crashes or other side effects, you may wish to consult your physician for evaluation and recommendations.