Caffeine is currently the world’s most commonly used drug. And because caffeine is present in so many common foods and drinks, it is easy to forget that it is a drug. It is even an ingredient in beverages and foods that are marketed to kids. But caffeine has significant effects of caffeine on the body and physical health.
Coffee, tea, cola, energy drinks—all of these beverages contain caffeine. And if you’re like many people, you consume one or more of these drinks every day.
Many of us rely on a morning cup of coffee or a jolt of caffeine in the afternoon to help us get through the day. Caffeine is so widely available that the U.S. Food and Drug Administration (FDA), says about 80 percent of U.S. adults take some form of caffeine every day. But caffeine does so much more than just keeping you awake. It’s a central nervous system stimulant that affects your body in numerous ways.
Caffeine is a stimulant drug—it may surprise you to realize that this is the same type of drug as cocaine and meth, substances we think of as hard drugs. Stimulant drugs work partly by stimulating the sympathetic nervous system, which causes the same physical effects as the “fight or flight response”—speeding up the heart and breathing, making you feel more alert, and increasing muscle tension. And when caffeine is consumed in large quantities, the side effects of caffeine can range from unpleasant to severe, sometimes even resulting in caffeine overdose.
Effects of Caffeine on the Body
Most people can consume up to 400 mg of caffeine in a day without any negative effects. If your caffeine intake is higher, you may experience one or more of the following health problems:
- Restlessness
- Shakiness
- Dizziness
- Rapid heart rate
- Anxiety
- Headache
- Dehydration
- Insomnia
Caffeine can also interfere with your body’s absorption of calcium, and excessive consumption may increase your blood pressure..
Central Nervous System
Caffeine acts as a central nervous system stimulant. When it reaches your brain, the most noticeable effect is alertness. You’ll feel more awake and less tired, so it’s a common ingredient in medications to treat or manage drowsiness, headaches, and migraines.
Studies have also found that people who drink coffee regularly have a lower risk of developing Alzheimer’s and dementia, and cut suicide risk by 45 percent. These benefits are limited to people who drink high-octane coffee, not decaf. Some people consider coffee to be a health drink, but like most foods, over indulging can cause side effects.
For example, too much caffeine can give you headaches. This is primarily linked to caffeine withdrawal. The blood vessels in your brain become used to caffeine’s effects so if you suddenly stop consuming caffeine, it can cause a headache.
Other symptoms of caffeine withdrawal include:
- anxiety
- irritability
- drowsiness
In some people, sudden withdrawal may cause tremors.
Although it’s extremely rare, it’s also possible to overdose on caffeine. Symptoms of an overdose include:
- confusion
- hallucinations
- vomiting
An overdose can result in death due to convulsions. Overdosing happens by consuming large amounts of caffeine, most often in energy drinks or diet pills. Up to 400 milligrams of caffeine is considered to be safe, according to the Mayo Clinic. This equals about 4 cups of coffee, although the amount of caffeine in beverages varies widely.
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.
For example, an energy shot may contain up to 350 mg of caffeine, while some energy drinks provide as much as a whopping 500 mg per can.
Importantly, the amount of caffeine you can consume without affecting your sleep will depend on your genetics and other factors.
In addition, caffeine consumed later in the day may interfere with sleep because its effects can take several hours to wear off.
Research has shown that while caffeine remains in your system for an average of five hours, the time period may range from one and a half hours to nine hours, depending on the individual.
One study investigated how the timing of caffeine ingestion affects sleep. Researchers gave 12 healthy adults 400 mg of caffeine either six hours before bedtime, three hours before bedtime or immediately prior to bedtime.
Both the time it took all three groups to fall asleep and the time they spent awake at night increased significantly.
These results suggest that it’s important to pay attention to both the amount and timing of caffeine to optimize your sleep.
Effects on the Heart
In simple terms, the stimulant effect of caffeine speeds up the heart rate. Research shows that the level of caffeine at which the heart rate is significantly affected is 400 milligrams, the equivalent of about four cups of brewed coffee.1
For most people who drink caffeine in moderation, this isn’t necessarily harmful—but for people who are prone to anxiety, this may increase the likelihood of panic reactions, because caffeine also increases anxiety, and people experiencing panic reactions often worry they are having a heart attack.
In higher doses, caffeine can cause more significant effects on the heart by changing the speed and regularity of your heartbeat. This is known as tachycardia or cardiac arrhythmia and can be serious. If you think your heartbeat is abnormal, check with your doctor.
It is unclear at the moment whether caffeine increases the risk of cardiovascular problems in the longer term. Several studies have indicated no increased risk for cardiovascular problems in either men or women related to caffeine intake, but current recommendations are that people who already have heart problems should avoid caffeine, as other studies show that these conditions can be exacerbated by caffeine and other stimulants.2 This includes children with cardiovascular problems, who may be exposed to caffeine through soda and energy drinks.
Drinking Large Amounts Of Coffee Can Cause A Spike In Blood Pressure and Heart Rate.
Studies have suggested that coffee increases heart rate, thanks to caffeine’s impact on hormones and neurotransmitters. But drinking coffee in moderation—one to three cups per day–shouldn’t have a noticeable impact on a healthy adult. According to the Mayo Clinic, some habitual drinkers may have a slightly higher blood pressure, while others develop a tolerance and are not affected in the long term. There isn’t a clear explanation as to why caffeine causes this increase in blood pressure, but it’s likely due to increased adrenaline and other hormonal responses brought on by the stimulant.
Digestive and Excretory Systems
Caffeine increases the amount of acid in your stomach and may cause heartburn or upset stomach. Extra caffeine doesn’t get stored in your body either. It’s processed in the liver and exits through your urine. This is why you might have an increase in urination shortly after having caffeine.
If you have experience stomach problems, like acid reflux or ulcers, ask your doctor if it’s okay for you to have caffeine.
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.
In a small study, when five healthy adults drank caffeinated water, they experienced a relaxation of the muscle that keeps stomach contents from moving up into the throat — the hallmark of GERD.
Since coffee can have major effects on digestive function, you may want to cut back on the amount you drink or switch to tea if you experience any issues.
Effects on Blood Pressure
Studies have conclusively shown that caffeine consumption raises blood pressure. This effect of caffeine, known as the “pressor effect,” is evident across age and gender groups, and is particularly pronounced in people with hypertension (high blood pressure).3 If you are unsure of whether this applies to you, it is a simple process to have your blood pressure checked by your physician and to get their advice on moderating your caffeine intake.
Effects on Bone Density
High coffee consumption has been linked to osteoporosis in men and women. Consumption of soft drinks in children is associated with lower bone mass, although this seems to be at least partially accounted for by those children who drink a lot of soft drinks also have a lower intake of milk.4 In older women, several studies have shown a link between high caffeine intake and lower bone density, while in younger women, this seems of particular concern when the women use progesterone-only contraceptives such as depot medroxyprogesterone acetate, or Depo Provera.
Coffee May Suppress Appetite And Boost Calorie Burn, But It’s Not A Magic Weight-Loss Bullet
Coffee is a known appetite suppressant and may stimulate thermogenesis, or the process our bodies use to create heat, which theoretically leads us to burn more calories. But there’s not much evidence that these effects are large enough to result in significant or long-term weight loss, the Mayo Clinic says. Black coffee is a good low-cal way to get your fix, but choking it down for its supposed weight-loss benefits probably won’t bring any noticeable changes.
Circulatory and Respiratory Systems
Caffeine is absorbed from your stomach. It reaches its highest levels in your bloodstream within an hour or two.
Caffeine can make your blood pressure go up for a short time. This effect is thought to be attributed to either an increase in adrenaline or a temporary block on the hormones that naturally widen your arteries. In most people, there is no long-term effect on blood pressure, but if you have irregular heart rhythms, caffeine may make your heart work harder. If you have high blood pressure (hypertension) or heart-related problems, ask your doctor if caffeine is safe for you to consume.
An overdose of caffeine may cause rapid or irregular heartbeat and breathing trouble. In rare cases, caffeine overdose can result in death due to convulsions or irregular heartbeat.
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.
In order to reduce the risk of rhabdomyolysis, it’s best to limit your intake to about 250 mg of caffeine per day, unless you’re used to consuming more.
Skeletal and Muscular Systems
Caffeine in large amounts may interfere with absorption and metabolism of calcium. This can contribute to bone thinning (osteoporosis).If you consume too much, caffeine may cause also your muscles to twitch.
If experiencing caffeine withdrawal, a symptom may include achy muscles.
Reproductive System
Caffeine travels within the bloodstream and crosses into the placenta. Since it’s a stimulant, it can cause your baby’s heart rate and metabolism to increase. Too much caffeine can also cause slowed fetal growth and increased risk of miscarriage. In most cases, a little caffeine is safe during pregnancy.
According to the Mayo Clinic, you should limit caffeine consumption between 200 and 300 milligrams per day if you’re trying to get pregnant. There’s some evidence that large amounts of caffeine can interfere with the estrogen production and metabolism needed to conceive.
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 similarly 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.
Additionally, the frequency of caffeine intake seems to play a role in dependency.
In another study, 213 caffeine users completed questionnaires after going 16 hours without consuming it. Daily users had greater increases in headaches, fatigue and other withdrawal symptoms than non-daily users).
Even though the compound does not seem to cause true addiction, if you regularly drink a lot of coffee or other caffeinated beverages, there’s a very good chance you may become dependent on its effects.
Fatigue
Coffee, tea and other caffeinated beverages are known to boost energy levels.
However, they can also have the opposite effect by leading to rebound fatigue after the caffeine leaves your system.
One review of 41 studies found that although caffeinated energy drinks increased alertness and improved mood for several hours, participants were often more tired than usual the following day.
Of course, if you continue to drink lots of caffeine throughout the day, you can avoid the rebound effect. On the other hand, this may affect your ability to sleep.
To maximize caffeine’s benefits on energy and avoid rebound fatigue, consume it in moderate rather than high doses.
Frequent Urination and Urgency
Increased urination is a common side effect of high caffeine intake due to the compound’s stimulatory effects on the bladder.
You may have noticed that you need to urinate frequently when you drink more coffee or tea than usual.
Most research looking at the compound’s effects on urinary frequency has focused on older people and those with overactive bladders or incontinence.
In one study, 12 young to middle-aged people with overactive bladders who consumed 2 mg of caffeine per pound (4.5 mg per kilogram) of body weight daily experienced significant increases in urinary frequency and urgency.
For someone weighing 150 pounds (68 kg), this would equate to about 300 mg of caffeine per day.
In addition, high intake may increase the likelihood of developing incontinence in people with healthy bladders.
One large study looked at the effects of high caffeine intake on incontinence in more than 65,000 women without incontinence.
Those who consumed more than 450 mg daily had a significantly increased risk of incontinence, compared to those who consumed less than 150 mg per day.
If you drink a lot of caffeinated beverages and feel that your urination is more frequent or urgent than it should be, it may be a good idea to cut back on your intake to see if your symptoms improve.
Other Claims Against Caffeine
You may have heard or read about other negative health effects from caffeine consumption, but as of now, there just isn’t enough evidence to fully endorse those as legitimate health concerns.
Some of those negatives include:
- Adrenal fatigue
- Irregular heartbeat
- Hallucinations
- Accelerates bone loss. Src.
- Tremors
Caffeine is a drug and can affect people differently just like any other substance. It’s important that consumers understand how caffeine interacts with their bodies in regard to their personal health histories. For some consumers, swapping morning coffee for a shot of ginger or another naturally energizing beverage could be a better alternative. Sprint Kitchen has some good recommendations.
The food and beverage industry spends millions, if not billions, of dollars worldwide to fund studies and promote caffeinated products as safe or even healthy.
Fortunately, caffeine is one of the most researched substances on the planet and there does exist some unbiased data from which to glean some reliable information from.
While much of the research published does allude to the safety and even potential benefits of caffeine (in moderation), there are a handful of research studies that highlight the potentially harmful effects of caffeine.
The risks of suffering from any of the harmful effects of caffeine are diminished by being aware of how much is personally being consumed daily.
It is also important to be aware of any pre-existing medical conditions that may contribute to caffeine’s negative effects.
