Caffeine is a stimulant derived from plants. Many beverages -- and even some foods -- contain caffeine, and many people swear by the energetic effects it has on the body. Sometimes, however, too much caffeine can have unpleasant side effects. How much is too much? It depends on one's tolerance level. Keeping alert is critical for most of us, but if you notice unpleasant effects, it may be time to minimize the amount of caffeine you ingest.


Caffeine's most notable property is alertness, although too much can cross the line into nervous. Anxiety is a common side effect of too much caffeine, and many people experience jitteriness, rapid speaking, and feelings of unease. One thousand milligrams of caffeine is considered high for daily intake and can result in both physical and mental manifestations of anxiety. Psychologists have a name for this effect: caffeine-induced anxiety disorder. To mitigate these effects, reduce caffeine intake and drink lots of water to help move the caffeine out of your system. Brisk walking can also help release some nervous energy.

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While caffeine might be just the ticket to help you wake up in the morning, too much can affect restful sleep at night. Many nutritional experts recommend avoiding caffeine after four pm to allow your body to purge it from your system completely. Caffeine may not just prevent people from falling asleep easily, it may also impact the restorative REM sleep, and its effects often increase as people age. Therefore, experts even more strongly recommend older people limit caffeine.

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Digestive Upset

Caffeine stimulates the nervous system and clears your thoughts -- but it also stimulates and clears the G.I. tract. Many people report excess caffeine results in frequent bowel movements or loose stools within an hour of ingestion. Those with Crohn's disease or irritable bowel syndrome find limiting caffeine can help ease symptoms of their condition. However, if you have a hard time producing bowel movements or experience constipation, a cup of coffee might help you get moving.

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Alertness and Sharper Thinking

Several studies note that compared to placebos, caffeine can improve memory. For students cramming for an exam -- or even those in the workplace trying to improve their performance -- the memory and cognition-boosting effects of caffeine can be beneficial. Caffeine dilates your blood vessels, making more blood available to the brain and boosting cognition. It can even increase oxygen saturation in the blood, making the blood delivered to the brain richer and more useful.

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Faster Glycogen Replenishment

Caffeine mixed with healthy carbohydrates can replenish the glycogen in your muscles as much as 66 percent faster after exercise. This is especially important for endurance athletes, as glycogen gives their bodies the energy to continue running, biking, or swimming. Caffeine can also mitigate oxidative stress on the joints and muscles and diminish inflammatory responses during endurance runs. It allows for better movement of the joints and faster recovery time.

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Improve Liver Health

Caffeine may help reduce fatty liver tissue for those with non-alcoholic fatty liver disease caused by conditions such as obesity. The stimulant works in part by increasing fat metabolism in the liver, and by reducing fatty tissue build up. Caffeine also reduces liver fibrosis risk in those with hepatitis C -- as little as 100 mg of caffeine per day can help reduce this side effect. For those who enjoy cleanses, a caffeine enema (administered under the direction of a health professional) may help cleanse and detoxify the liver.

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Fast Pulse and Elevated Blood Pressure

As caffeine stimulates the body, it also increases the resting and active heart rates. A fast pulse or fluttery feeling is a common effect of too much caffeine. Excess caffeine can also alter the rhythm of the heart, a condition known as atrial fibrillation. High-caffeine energy drinks are a common cause, especially when those drinking them don't typically consume much caffeine. However, those who lift heavy swear by the added boost; these "pre-workout" drinks and supplements can give them the energy and extra blood flow necessary for lifting heavy weights.

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Sudden Fatigue

Caffeine is powerful enough to provide a big boost to energy levels and clear the cobwebs from the brain, but it also can result in a sudden crash, especially for individuals who are dehydrated or not well-rested. Sudden fatigue from excess caffeine can be especially dangerous when on the road. Choosing to "rebound" the fatigue can lead to insomnia and poor sleep -- to avoid this cycle, reduce the amount of caffeine consumed at one time.

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Reduce Kidney Stone Risk

The liver isn't the only excretory organ that benefits from caffeine. Studies link moderate caffeine consumption to fewer incidences of kidney stones. Caffeine dilutes urine, reducing the concentration of toxins that cause kidney stones. This can lead to those compounds being safely removed from the body instead of remaining in the kidneys and turning into painful deposits. Studies also indicate a link between the progression of kidney disease and caffeine consumption. Caffeine-consuming people with kidney disease show a slower progression, as well as a lower mortality rate.

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High Caffeine Foods and Beverages

Coffee is high in caffeine. Even decaf coffee has about the same amount of caffeine as green tea. Some stronger teas, such as black or Earl Grey, have higher amounts of caffeine, while herbal teas are caffeine-free and can serve as a substitute. Almost all sodas have caffeine, as well -- furthermore, the high sugar content can exacerbate some of caffeine's effects. Chocolate also has plenty of caffeine, with dark chocolate (which contains less sugar and milk) having the highest concentration. Caffeine supplements are available over the counter, as well -- be sure to read the package to determine the correct amount for your body and tolerance.

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