How Caffeine Affects Your Body, From Your Brain to Your Bladder

There are both positive and negative side effects of drinking coffee and other caffeinated beverages.
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Whether it's a morning cup of joe, afternoon Diet Coke or pre-gym energy drink, many of us look to caffeinated beverages for a little extra boost.

Indeed, according to a January 2014 study published in ​Food and Chemical Toxicology,​ a whopping 85 percent of Americans down at least one caffeinated drink per day.


But have you ever wondered ​how​ caffeine works its magic? From your brain to your bowels, caffeine can have a number of effect on your body — from first sip to after-effects.

We'll examine the effects of caffeine on the body, as well as any potential downsides to coffee and other caffeinated food and drinks.

The Effects of Caffeine on Your Body

Caffeine — coffee and beyond — can affect the body in many different ways. Below are five ways caffeine may impact your system.


1. You Feel More Alert

The short-term effects of caffeine are the reason so many people around the world enjoy it first thing in the morning.

As a stimulant, caffeine affects your central nervous system, including dilating the blood vessels in your brain, which makes you feel more awake and alert. "The effect can be fairly immediate," says registered dietitian Laura Burak, RD. That near-instant effect is why so many coffee-lovers count on a cup of brew to perk them up in the morning.


Drinking coffee may affect how well you perform at work or school, as caffeine and short-term memory seem to have a positive relationship. A January 2014 study published in ​Nature Neuroscience​ found that caffeine can improve memory consolidation — the process of committing what we've learned to long-term memory — for up to 24 hours after it's consumed.

2. Your Heart Rate and Blood Pressure Increase

Temporarily upping blood pressure is one of the many ways caffeine can affect your body.
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Caffeine may cause a temporary spike in your heart rate and blood pressure, according to the Mayo Clinic. This short-lived boost is likely linked to an increase in adrenaline and other hormonal reactions triggered by the stimulant.


But caffeine affects everyone differently. "While some may feel their blood pressure and heart rate rise immediately, others with a higher tolerance will not feel any effect," Burak says.

Fortunately, for coffee-lovers, 400 milligrams of caffeine a day (that's four to five cups), doesn't appear to create any serious health problems, per the USDA. That said, Burak recommends that people with a history of heart disease limit their caffeine intake.

3. Your Workouts May Get a Boost

In addition to your central nervous system and heart, caffeine stimulates your muscles. In fact, it may do wonders for your workouts. Caffeine has been shown to improve endurance, Burak says. While some effect can be felt right away, caffeine's impact on your muscles tends to peak around the 45-minute mark, when it has reached full concentration in your bloodstream.

Plus, caffeine can enhance strength training and performance, per the American Council of Exercise. A March 2018 meta-analysis of 20 studies, published in the ​Journal of the International Society of Sports Nutrition​, found that caffeine consumption improved both muscle strength and power when ingested before exercise, and especially upper body strength. However, the researchers noted that additional studies need to be done to determine which forms of caffeine are most effective.

Are you on track to achieve your fitness goals? Download the MyPlate app to keep tabs on the number of calories you burn during your workouts and stay motivated.

Finally, Burak says caffeine has been shown to decrease muscle soreness after exercise, an effect that may be related to its antioxidant properties, which help decrease inflammation in the body.

4. You May Need to Pee

Caffeine is a natural diuretic, which means it may increase your number of trips to the restroom.
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Caffeine is a natural diuretic, which means, in layman's terms, that it makes you pee. "Caffeine creates blood flow to the kidneys, where liquid is processed," explains Burak, adding that drinking a large mug or thermos of coffee or tea every morning may be the culprit behind frequent trips to the bathroom.

So, when will the urge to go strike? That depends on your size, metabolism and caffeine intake. Typically, though, your bladder will need emptying within one to two hours of ingesting a caffeinated drink, according to Burak.

5. And You'll Probably Need to Poo, Too

Ever notice the impulse to poop after sipping your morning brew? That's because "caffeine, especially that in coffee, stimulates your gastrointestinal tract and creates peristalsis, or that wave-like pattern that moves contents through your intestines and to your bowel," says Burak.

Once again, a host of factors affect how quickly this happens. So some people may feel the effects immediately, while others may have a delayed urge to hit the restroom.

The Downsides of Drinking Caffeine

For some, it can be hard to imagine any disadvantages of coffee. And yet, there are some potentially bad side effects of drinking coffee.

While drinking coffee isn't bad for you, some people can experience negative effects from caffeine. Although caffeine is widely consumed, it still is considered a drug and it comes with some potential disadvantages.

While you may not be especially sensitive to caffeine, there are some telltale signs that you've had too much, according to the Cleveland Clinic. These include:

  • Headache
  • Nervousness
  • Dizziness
  • Experiencing "the jitters" or feeling shaky
  • Insomnia
  • Racing heart or abnormal heartbeat
  • Increase in blood pressure
  • Dehydration

In the long term, drinking a lot of caffeine throughout the day might lead to a vicious cycle of insomnia and fatigue, wherein you consistently lose sleep because of caffeine's effects, but then you need to drink caffeine to be alert during the day.

Some studies have found a link between coffee and increased cholesterol. Coffee itself does not contain cholesterol, but the culprit here may be cafestol, an oil that is naturally present in coffee beans. One early February 2001 study in ​Epidemiology​ found that coffee oils may decrease bile acids and neutral sterols, a process that may lead to higher cholesterol levels.

Still, more research is needed to understand the link between coffee and cholesterol. Some research has found that different brewing methods can filter out amounts of cafestol. While some people say that K-cups by Keurig filter out cafestol, more research is needed.

Filtered vs. Unfiltered Coffee

Is unfiltered coffee bad for you?

An April 2020 study in the ​European Journal of Preventive Cardiology​ in April examined the coffee habits of 508,747 men and women between the ages of 20 and 79, finding that drinking unfiltered coffee was associated with higher rates of heart disease and death than drinking filtered coffee.

Over half of participants (59 percent) preferred filtered coffee, 20 percent drank unfiltered coffee, 9 percent consumed both brews and 12p percent drank no coffee at all.

According to the researchers, coffee drinkers who consumed between one and cups of filtered coffee daily had the lowest mortality, while those that drank nine cups of unfiltered coffee per day had the highest mortality.

More research is needed to fully understand the health effects of unfiltered coffee. Something we do know? Excess cream and sugar won't do your health any favors.

Caffeine Sensitivity

Some people are more sensitive to caffeine — and there can be many different explanations as to why that might be. The National Institutes of Health (NIH) recommends limiting your caffeine intake if:

  • You are prone to stress, anxiety or sleep problems
  • You are a woman with painful, lumpy breasts
  • You have acid reflux or stomach ulcers
  • You have high blood pressure that drops with medicine
  • You have problems with fast or irregular heart rhythms
  • You have chronic headaches

If you are extra-sensitive to caffeine, even a single cup of coffee could prompt undesirable effects, such as restlessness.


Caffeine can raise your body temperature, along with your heart rate and blood pressure.

Although sweating is not a common effect of caffeine, it does occur in some individuals, per the U.S. National Library of Medicine. Sweating from caffeine is more likely when someone consumes a large amount of caffeine.

If you tend to gravitate toward the maximum recommendation of 400 milligrams of caffeine a day, you may experience side effects like sweating, according to the Mayo Clinic.

The sweating is generally not a cause for concern and should go away on its own when the caffeine is metabolized and excreted from the body. However, if you are concerned about your sweating, call your doctor.


Moderate amounts of caffeine are not likely to cause uncontrollable sweating. But if you have any health issues that are triggered by caffeine, you may experience an increase in sweat production.

Certain medical conditions may interact negatively with caffeine. Menopausal women may want to take note in particular if they find themselves sweating from caffeine.

A July 2014 study in the journal Menopause found an association between caffeine intake and an increase in hot flashes and night sweats in postmenopausal women. Based on these preliminary findings, the researchers suggest that limiting caffeine may help reduce the severity of both night sweats and hot flashes.

While sweating uncontrollably is not typically a side effect of caffeine use, if you have a medical condition called hyperhidrosis, you may experience an increase in sweating triggered by stimulants such as caffeine.

Sweating also may be a response to strong emotions, such as nervousness, anger, embarrassment or fear. Hormonal changes, illness, low blood sugar, an overactive thyroid, spicy foods, warm temperatures, cancer, alcohol and certain medications may also trigger sweating. Eliminating caffeine completely can help you determine if the sweating is due to caffeine or because of one of these other conditions.

Caffeine and Medications

If you're taking certain medications or supplements, you'll want to be mindful about your caffeine consumption. The following medications may interact negatively with caffeine, per the Mayo Clinic, but they're not the only kinds to do so. For this reason, it is recommended to talk with your doctor or pharmacist about the potential adverse effects of mixing your prescriptions with caffeine.

  • Ephedrine:​ Mixing caffeine with ephedrine, an ingredient in decongestants, may increase your risk of high blood pressure, heart attack, stroke or seizure.
  • Theophylline:​ This medication, used to open up bronchial airways, tends to have some caffeine-like effects. Taking it with caffeine might increase the adverse effects of caffeine, such as nausea and heart palpitations.
  • Echinacea:​ This herbal supplement, which is sometimes used to prevent colds or other infections, may increase the concentration of caffeine in your blood and may increase caffeine's undesirable side effects.

Caffeine is sometimes used as an ingredient in certain medications — both over-the-counter and prescriptions, per the Cleveland Clinic. Caffeine's effects on the central nervous system can help some drugs work more effectively, particularly pain relievers.

Caffeine and Pregnancy

People are often advised to keep their caffeine intake to a minimum while pregnant — the NIH says drinking one to two small cups of caffeinated coffee or tea a day (240 to 480 milliliters) is considered safe.

Just like alcohol, caffeine travels through your bloodstream to the placenta. Drinking too much caffeine can have a negative effect on a developing baby.

Even coffee can pose health risks. Because caffeine is a stimulant, it increases your heart rate and metabolism, both of which can affect the baby.

Caffeine Dependency

Caffeine is the most widely used drug in the world, and while is generally considered safe, an increasing amount of research shows that some people can become dependent on it.

Many people develop a tolerance for caffeine, and some people may show signs of a dependency through certain behaviors, according to a September 2013 review in the ​Journal of Caffeine Research.​ These behaviors include a persistent desire or unsuccessful efforts to cut down or control caffeine use, continued use despite harm, and a characteristic withdrawal syndrome.

One of the clearest signs of caffeine dependency is an inability to perform routine activities without caffeine. Early September 2004 research in ​Psychopharmacology​ highlights some common withdrawal symptoms, which include:

  • Headache
  • Low energy
  • Decreased alertness
  • Difficulty concentrating
  • Irritability
  • Feeling foggy

How to Cut Back on Your Caffeine Intake

The recommended amount of caffeine per day is up to 400 milligrams, which is considered safe for most adults, according to the Mayo Clinic.

While that sounds like a lot of caffeine, if you're accustomed to drinking several cups of coffee a day, you might be surprised to learn that four cups of brewed coffee is approximately 400 milligrams.

When you add that to the other sources of caffeine such as energy drinks, soda, tea, chocolate, coffee-flavored ice cream, energy bars and smoothies, it's easy to see how quickly the amount can add up.

You may want to cut back your caffeine for a host of different reasons, one being to reduce any bad side effects of drinking coffee.

In most cases, it's not recommended to go cold turkey, as doing so can trigger some of the adverse effects associated with withdrawal — especially headaches.

Instead of cutting out caffeine all at once, work to gradually reduce the amount of coffee, tea, soda and energy drinks you consume each day, advises the Cleveland Clinic.

You might try substituting some of your typical caffeinated drinks with water, which can help flush caffeine from your body while keeping you hydrated.

If you're a coffee-drinker, make a gradual switch from regular to decaf coffee. If you're having several cups a day, start by switching at least one of those cups to decaf, and continue to increase your decaf intake over the next few weeks.

Cutting back on your caffeine consumption over a two-to-three week period can help you change your habit without the negative effects of withdrawal.