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What are the negative effects of caffeine?

The negative effects of caffeine are well documented, but not all research agrees on the results of caffeine. Some is specifically caffeine negative, citing numerous bad effects. Other studies take a more positive approach and cite both benefits and possible problems with caffeine consumption. Most studies correlate the negative effects with high caffeine intake, and with certain physical conditions or groups of people who tend to have more problems with caffeine.

A small amount of caffeine intake by a completely healthy person may have minimal effect. Caffeine is a stimulant and it will elevate heart rate, increase blood flow, and raise body temperature. It increases blood sugar levels and act as a diuretic, meaning you urinate more frequently and reduce water intake. Caffeine makes most users more alert, and some studies have suggested that it may reduce the risk of diseases like Parkinson's. People with certain conditions, or who consume large amounts of caffeine, may suffer more negative effects, however.

One of the negative effects of caffeine is that small amounts taken daily can create a physical dependence. If a regular coffee drinker, for example, fails to drink his daily dose of caffeine, he can end up with headaches, excessive sleepiness, a feeling like he cannot function. Withdrawal from caffeine can take anywhere from a few days to a few weeks depending upon how much caffeine a person customarily consumes.

When caffeine intake is above 300 milligrams a day, about three cups of coffee or three to four sodas, the caffeine may at first make a person feel energized. Yet one of the negative effects of caffeine is its ability to disrupt sleep cycles, causing less deep sleep, particularly when the person drinks caffeinated beverages within a few hours of bedtime. So while a person may be using coffee or other caffeine laced beverages to "get started" in the morning, one reason he might need this extra boost because he is getting inadequate sleep.

In 2006, studies on night shift workers found that those who consume caffeine at night are most prone to this effect. Since night shift work already disrupts normal sleeping patterns, caffeine intake may create more serious issues. Those who drink caffeinated beverages and work the night shift have a far greater likelihood of getting insufficient deep sleep during the day. This can result in a continued cycle of exhaustion and caffeine boosts, a greater dependence on caffeine, and more caffeine consumed, which only exacerbates the problem.

Certain people are also particularly caffeine sensitive and more likely to experience negative effects of caffeine. For example, some people will feel "buzzed" or hyped up from one cup of coffee. Lower body weight tends to translate to higher likelihood of experiencing the negative side effects.

People with panic disorder or generalized anxiety disorder are much more prone to reacting badly from increased heart rate. Caffeine, even in small doses, can create panic attacks and interfere with medications taken to calm the system. Caffeine is an adenosine-receptor antagonist, meaning that it blocks the receptors in the brain that bind with the neuromodulator adenosine, which slows neural activity. It also promotes the release of adrenaline and dopamine.

For people with high blood pressure or high blood sugar levels, the negative effects of caffeine should be understood. Caffeine can raise both these levels. Any type of heart problem can be affected by caffeine. The negative effect of caffeine in increasing heart rate can create problems for people with heart conditions, and in high doses, caffeine can induce irregular heartbeats in healthy people.

People with stomach conditions like irritable bowel syndrome, Crohn's disease, ulcers, and gastro-intestinal reflux, may all suffer from consuming caffeine. Caffeine increases acidic response in the stomach which may lead to excessive bowel movements and is associated with stomach discomfort.

Negative effects of caffeine can be broken down into moderate and serious side effects:

Moderate effects include:

  • Headaches
  • Irritability
  • Increase in breast tenderness
  • Restlessness
  • Mild insomnia
  • Increased heart rate
  • Increased blood sugar
  • Difficulty concentrating
  • Mild stomach upset


Severe effects include:

  • Panic attacks
  • Irregular heartbeat
  • Sleep deprivation
  • Continuous stomach problems
  • Prolonged depression
  • Sleep disorders


Though there are some positive effects of caffeine, the negative should be understood. Anyone in a high-risk group should be aware of the severe negative effects. People with mood disorders, high blood pressure, diabetes, heart disease, kidney disease, chronic intestinal issues, work the night shift or who are pregnant should minimize caffeine intake.



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