Most types contain caffeine, a substance that may boost your mood, metabolism and mental and physical performance. Studies have also shown that it’s safe for most people when consumed in low-to-moderate amounts. However, high doses of caffeine may have unpleasant and even dangerous side effects. Research has shown that your genes have a major influence on your tolerance to it. Some can consume much more caffeine than others without experiencing negative effects.
What’s more, individuals who aren’t used to caffeine may experience symptoms after consuming what is typically considered a moderate dose.
Here are some side effects of too much caffeine.
1. Anxiety
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, leading to anxiety and nervousness.
In fact, caffeine-induced anxiety disorder is one of four caffeine-related syndromes listed in the Diagnostic and Statistical Manual of Mental Disorders (DSM), which is published by the American Psychiatric Association.
Extremely high daily intakes of 1,000 mg or more per day have been reported to cause nervousness, jitteriness and similar symptoms in most people, whereas even a moderate intake may lead to similar effects in caffeine-sensitive individuals.
Additionally, modest doses have been shown to cause rapid breathing and increase stress levels when consumed in one sitting.
2. Insomnia
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 amount of time it takes to fall asleep. It may also decrease total sleeping time, especially in the elderly.
By contrast, low or moderate amounts of caffeine don’t seem to affect sleep very much in people considered “good sleepers,” or even those with self-reported insomnia. You may not realize that too much caffeine is interfering with your sleep if you underestimate the amount of caffeine you’re taking in.
Although coffee and tea are the most concentrated sources of caffeine, it is also found in soda, cocoa, energy drinks and several types of medication.
3. Digestive Issues
Many people find that a morning cup of coffee helps get their bowels moving. Coffee’s laxative effect has been attributed to the release of gastrin, a hormone the stomach produces that speeds up activity in the colon. What’s more, decaffeinated coffee has been shown to produce a similar response.
However, caffeine itself also seems to stimulate bowel movements by increasing peristalsis, the contractions that move food through your digestive tract. Given this effect, it’s not surprising that large doses of caffeine may lead to loose stools or even diarrhea in some people.
Although for many years coffee was believed to cause stomach ulcers, a large study of more than 8,000 people didn’t find any link between the two. On the other hand, some studies suggest that caffeinated beverages may worsen gastroesophageal reflux disease (GERD) in some people. This seems to be especially true of coffee.
4. Muscle Breakdown
Rhabdomyolysis is a very serious condition in which damaged muscle fibers enter the bloodstream, leading to kidney failure and other problems. Common causes of rhabdomyolysis include trauma, infection, drug abuse, muscle strain and bites from poisonous snakes or insects. In addition, there have been several reports of rhabdomyolysis related to excessive caffeine intake, although this is relatively rare.
In one case, a woman developed nausea, vomiting and dark urine after drinking 32 ounces (1 liter) of coffee containing roughly 565 mg of caffeine. Fortunately, she recovered after being treated with medication and fluids.
Importantly, this is a large dosage of caffeine to consume within a short period of time, especially for someone who isn’t used to it or is highly sensitive to its effects.
5. Addiction
Despite all of caffeine’s health benefits, there’s no denying that it may become habit-forming. A detailed review suggests that although caffeine triggers certain brain chemicals similar to the way cocaine and amphetamines do, it does not cause classic addiction the way these drugs do.
However, it may lead to psychological or physical dependency, especially at high dosages.
In one study, 16 people who typically consumed high, moderate or no caffeine took part in a word test after going without caffeine overnight. Only high caffeine users showed a bias for caffeine-related words and had strong caffeine cravings
6. High Blood Pressure
Overall, caffeine doesn’t seem to increase the risk of heart disease or stroke in most people. However, it has been shown to raise blood pressure in several studies due to its stimulatory effect on the nervous system. Elevated blood pressure is a risk factor for heart attack and stroke because it may damage arteries over time, restricting the flow of blood to your heart and brain.
Fortunately, caffeine’s effect on blood pressure seems to be temporary. Also, it seems to have the strongest impact on people who aren’t used to consuming it.
High caffeine intake has also been shown to raise blood pressure during exercise in healthy people, as well as in those with mildly elevated blood pressure.
7. Rapid Heart Rate
The stimulatory effects of high caffeine intake may cause your heart to beat faster. It may also lead to altered heartbeat rhythm, called atrial fibrillation, which has been reported in young people who consumed energy drinks containing extremely high doses of caffeine. In one case study, a woman who took a massive dose of caffeine powder and tablets in an attempted suicide developed a very rapid heart rate, kidney failure, and other serious health issues.
However, this effect doesn’t seem to occur in everyone. Indeed, even some people with heart problems may be able to tolerate large amounts of caffeine without any adverse effects.
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