Coffee and tea are very healthy drinks.

Most types contain caffeine, a substance that can improve your mood, metabolism, and mental and physical performance.

Research also shows that it is safe for most people when consumed in small to moderate amounts.

However, high doses of caffeine can have unpleasant or even dangerous side effects.

Research shows that your genes have a significant impact on your tolerance. Some people can consume more caffeine than others without negative effects .

Additionally, people who are not accustomed to caffeine may experience symptoms after consuming what is typically considered a moderate dose of caffeine .


Caffeine is known to increase alertness.

It works by blocking the effects of adenosine, a brain chemical that makes you feel tired. At the same time, it triggers the release of adrenaline, the "fight or flight" hormone associated with increased energy.

However, at higher doses, these effects may become more pronounced, causing anxiety and nervousness.

In fact, caffeine-induced anxiety is one of four caffeine-related syndromes listed in the Diagnostic and Statistical Manual of Mental Disorders (DSM), published by the American Psychiatric Association.

Extremely high doses of 1,000 mg or more per day have been reported to cause jitteriness, restlessness and similar symptoms in most people, while even moderate intakes may cause similar effects in caffeine-sensitive people.

Additionally, moderate doses have been shown to cause shortness of breath and increase stress levels when consumed in one sitting.

One study of 25 healthy men found that those who consumed about 300 milligrams of caffeine experienced more than twice as much stress as those who took a placebo.

Interestingly, cortisol levels were similar between regular and infrequent caffeine drinkers, suggesting that this compound may have the same impact on stress levels whether you're a habitual caffeine drinker or not.

However, these results are preliminary.

The caffeine content of coffee varies widely. For reference, a "grande" cup of coffee from Starbucks contains about 330 milligrams of caffeine.

If you find that you often feel jittery or jittery, it's a good idea to check your caffeine intake and cut back.


Caffeine's ability to help people stay awake is one of its most prized qualities.

On the other hand, too much caffeine can make it difficult to get enough restorative sleep.

Studies have found that higher caffeine intake appears to increase the time it takes to fall asleep. It may also reduce total sleep time, especially in older adults.

In contrast, low or moderate amounts of caffeine do not appear to have much of an impact on the sleep of those who are considered "good sleepers" or even those who self-report insomnia.

If you underestimate how much caffeine you consume, you may not realize that too much caffeine can disrupt your sleep.

While coffee and tea are the most concentrated sources of caffeine, caffeine is also found in soda, cocoa, energy drinks, and several medications.

For example, a cup of energy drink may contain up to 350 mg of caffeine, and some energy drinks contain up to 505 mg of caffeine per can.

Importantly, the amount of caffeine you can consume without disrupting your sleep depends on your genetics and other factors.

Additionally, caffeine consumed later in the day may interfere with sleep, as its effects may take several hours to wear off.

Research shows that while caffeine remains in your system for an average of five hours, that time period can vary from one and a half to nine hours, depending on the individual.

One study examined how the timing of caffeine intake affects sleep. Researchers asked 12 healthy adults to take 400 milligrams of caffeine 6 hours before bed, 3 hours before bed, or just before bed.

The time it took for all three groups to fall asleep and the amount of time they were awake during the night increased significantly.

These results suggest that paying attention to the amount and timing of caffeine intake is important to optimize sleep.

digestive problems

Many people find that drinking a cup of coffee in the morning helps with bowel movement.

The laxative effect of coffee is attributed to the release of gastrin, a hormone produced by the stomach that speeds up the activity of the colon. Additionally, decaf coffee has been shown to produce a similar response.

Given this effect, it's not surprising that large doses of caffeine may cause loose stools or even diarrhea in some people.

Although coffee has been thought to cause stomach ulcers for years, a large study of more than 8,000 people found no link.

On the other hand, some studies suggest that caffeinated drinks may worsen gastroesophageal reflux (GERD) in some people. This seems to be especially true with coffee.

In one small study, when five healthy adults drank caffeinated water, they experienced muscle relaxation that prevents stomach contents from moving up into the throat—a sign of gastroesophageal reflux.

Since coffee can have a significant impact on digestion, you may want to cut back on the amount you drink or switch to tea if you experience any problems.

muscle breakdown

Rhabdomyolysis is a very serious disease in which damaged muscle fibers can enter the bloodstream, causing kidney failure and other problems.

Common causes of rhabdomyolysis include trauma, infection, drug abuse, muscle strain, and snake or insect bites.

Additionally, there have been several reports of rhabdomyolysis associated with excessive caffeine ingestion, although this is relatively rare.

In one case, a woman experienced nausea, vomiting, and dark urine after drinking 32 ounces (1 liter) of coffee containing approximately 565 mg of caffeine. Fortunately, she recovered with medication and fluids.

Importantly, this is a reason to consume large amounts of caffeine in a short period of time, especially for those who are not used to it or are highly sensitive to its effects.

To reduce the risk of rhabdomyolysis, it's best to limit your daily caffeine intake to around 400 milligrams, unless you're used to consuming more.


Although caffeine has many health benefits, there is no denying that it can be addictive.

A detailed review suggests that although caffeine triggers certain brain chemicals like cocaine and amphetamines, it does not cause classic addiction like these drugs.

However, it may cause psychological or physical dependence, especially at high doses.

In one study, 16 people who usually consumed high, moderate or no caffeine took a single-word test after going caffeine-free overnight. Only high caffeine users showed a bias toward caffeine-related words and had a strong craving for caffeine.

Additionally, the frequency of caffeine intake appears to have an impact on dependence.

In another study, 213 caffeine users completed questionnaires after 16 hours without coffee. Daily users experienced greater increases in headaches, fatigue, and other withdrawal symptoms than non-daily users.

Although this compound does not appear to cause true addiction, if you regularly drink large amounts of coffee or other caffeinated beverages, there is a good chance that you may become dependent on its effects.


Overall, caffeine does not appear to increase the risk of heart disease or stroke in most people.

However, multiple studies have shown that it can increase blood pressure due to its stimulating effects on the nervous system.

Elevated blood pressure is a risk factor for heart attacks and strokes because, over time, it can damage arteries and restrict blood flow to the heart and brain.

Fortunately, caffeine's effects on blood pressure appear to be temporary. Additionally, it seems to have the greatest impact on people who are not used to eating it.

Studies have also shown that high amounts of caffeine consumed during exercise can increase blood pressure in both healthy people and people with mildly elevated blood pressure.

Therefore, it's important to pay attention to your caffeine dosage and timing, especially if you already have high blood pressure.

Heart rate too fast

The stimulating effects of high caffeine intake may cause your heart to beat faster.

It can also cause a change in heart rate called atrial fibrillation, which has been reported in young people who drink energy drinks containing extremely high doses of caffeine.

In one case study, a woman developed a rapid heart rate, kidney failure and other serious health problems after taking large amounts of caffeine powder and pills in an attempted suicide.

However, this effect doesn't seem to happen to everyone. In fact, even some people with heart disease may be able to tolerate large amounts of caffeine without any side effects.

In a controlled study, when 51 heart failure patients took 100 mg of caffeine every hour for 5 hours, their heart rates and rhythms remained normal.

Regardless of study results, if you notice any changes in your heart rate or rhythm after drinking caffeinated beverages, consider reducing your intake.


Coffee, tea, and other caffeinated beverages are known to increase energy levels.

However, they can also have the opposite effect, causing fatigue to rebound after the caffeine leaves your system.

A review of 41 studies found that although caffeinated energy drinks increased alertness and improved mood for several hours, participants tended to be more tired than usual the next day.

To maximize the energy benefits of caffeine and avoid a fatigue rebound, consume it in moderation rather than large amounts.

Frequent urination and urgency

Increased urination is a common side effect of high caffeine intake because of the irritating effects of this compound on the bladder.

You may have noticed that when you drink more coffee or tea than usual, you need to urinate more often.

Most studies examining the compound's effects on frequent urination have focused on older adults and people with overactive bladders or urinary incontinence.

In one study, 12 young to middle-aged people with overactive bladder who consumed 2 mg of caffeine per pound of body weight per day (4.5 mg/kg) experienced significant increases in frequency and urgency of urination.

For a person weighing 150 pounds (68 kg), this is equivalent to about 300 milligrams of caffeine per day.

Additionally, high intake may increase the likelihood of urinary incontinence in people with healthy bladders.

One large study examined the effects of high amounts of caffeine on incontinence in more than 65,000 women who were not incontinent.

People who consumed more than 450 mg per day had a significantly increased risk of incontinence compared with those who consumed less than 150 mg per day.

If you drink a lot of caffeinated drinks and feel like you're urinating more frequently or more urgently than you should, it might be a good idea to reduce your intake and see if your symptoms improve.


Low to moderate caffeine intake appears to be beneficial to the health of many people.

On the other hand, very high doses may cause side effects, interfere with daily life, and may even lead to serious health problems.

Although responses vary from person to person, the effects of high intakes suggest that more is not necessarily better.

To get the benefits of caffeine without the adverse effects, make an honest assessment of your sleep, energy levels, and other factors that may be affected, and reduce your intake if needed.


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