How Caffeine Affects Your Body

About 75% of adults in the United States drink coffee, which is widely known for its caffeine content. Consuming caffeine can boost your energy levels and enhance your cognition in the short term, but it can also lead to restlessness, anxiety, and dependency when consumed in excess.

Coffee isn’t the only source of naturally occurring caffeine. Caffeine is also found naturally in some tea leaves, kola nuts used in colas, and cacao pods used to make chocolate products. Energy drinks are also high in synthetic forms of caffeine. These sources of caffeine can all affect your body in different ways.

The most common known effect of caffeine is increased energy levels. Through blocking adenosine receptors, it staves off sleepiness and makes you feel more awake. These beneficial effects are seen at doses under 400 mg, which is the suggested daily limit. Consuming too much caffeine, on the other hand, is associated with nervousness, tension, anxiety, and restlessness.

Multiple studies have also found coffee drinkers have lower rates of Alzheimer’s disease and dementia. The same was not found for tea. There may be other compounds in coffee that affect this risk, rather than caffeine itself. This is an area of interest for researchers, and more studies are needed to examine other compounds in caffeinated products that may affect brain health. 

Caffeine has been shown to moderately improve various aspects of athletic performance in the short-term.

Research has shown doses of 3–6 mg of caffeine per kilogram of body weight to have benefits on muscular endurance and strength, movement velocity, sprinting, jumping, and throwing. However, the effects can vary based on the individual.

The researchers found it was usually most helpful to consume caffeine about 60 minutes before exercise. They also noted caffeine can offer benefits to various aerobic exercises, like swimming and biking, and anaerobic exercises, like weight lifting.

Caffeine marketed for athletic performance benefits can be found in many forms including gels, pre-workout supplements, chewing gum, or mouth rinses. 

If you’re a coffee drinker, you may find that it’s key to keeping you regular. That’s partly because caffeine may promote gastrointestinal motility, meaning it helps move food through the intestine and out of the body.

Some studies have found caffeine is just as effective as a meal and much more effective than water or decaffeinated coffee at stimulating colonic motor activity. For this reason, many people rely on coffee for regular bowel movements or to prevent constipation. 

Some research has shown a connection between caffeine consumption and better heart health.

A review of studies on heart health found increased coffee consumption was linked to reduced risk of developing heart failure later in life. Researchers aren’t yet sure if this is a causal (direct) link or what about caffeine may impact heart health.

Another study found higher green tea and coffee consumption was linked to lower risk of cardiovascular disease and stroke.

However, consuming caffeine has also been shown to increase your blood pressure, especially when consumed in high amounts. For example, one study found consuming a 32-ounce energy drink with over 300 mg of caffeine greatly increased blood pressure compared to a placebo in young adult participants.

Lower doses of caffeine don’t seem to have the same effect on raising blood pressure, particularly among habitual users.

Natural sources of caffeine are rich in antioxidants, which are compounds that help reduce the amount of free radicals in your body that cause oxidative stress.

Antioxidants in naturally occurring sources of caffeine also have anti-inflammatory properties that may help reduce the risk of developing certain diseases, like liver disease.

Oxidative stress can also result from ultraviolet (UV) light and cause skin damage. The antioxidants in caffeine may help protect skin cells from UV damage. 

Caffeine may have many potential benefits. Smaller studies have shown caffeine may:

• Increase your pain threshold
• Decrease your risk of depression
• Support immune, digestive, and respiratory health

There are a few potential side effects of caffeine. While these side effects are more likely if you consume caffeine in excess, they may occur even if you consume less than the recommended maximum intake, depending on your sensitivity to caffeine.

Caffeine’s action on adenosine can block you from feeling the depressant effects of alcohol. Since you won’t feel alcohol’s usual effects, having it with caffeine can lead you to consume alcohol in excess. So, you should not pair these two substances together.

Foods and drinks with caffeine, like soda, coffee drinks, bottled tea, or energy drinks, also tend to have added sugars. Added sugars are linked with conditions like type 2 diabetes and heart disease, so it’s recommended you limit your intake of added sugar to no more than 10% of your total caloric intake.

To reduce your added sugar consumption in caffeinated drinks, try brewing coffee or tea at home and adding a splash of cream. You can also consume dark chocolate, which is lower in added sugar than milk or white chocolate. 

Caffeine’s stimulating effects can also cause short-term appetite suppression. As a result, it can be misused by people with disordered eating or an eating disorder to avoid eating an adequate amount of food. Even if you aren’t doing it intentionally, if you rely heavily on caffeine-rich foods and drinks, you may have an insufficient food intake. 

Other potential side effects of caffeine, particularly too much caffeine, include:

• Restlessness
• Dizziness
• Insomnia
• Headaches
• Rapid heart rate
• Dehydration
• Anxiety

Caffeine is a bitter-tasting stimulant substance found naturally in over 60 plants including coffee beans, tea leaves, kola nuts, and cacao pods. It can also be made synthetically. The synthetic form is added to energy drinks and certain drugs, like pain relievers and cold medications. 

You may use caffeine to help wake yourself up in the morning or to counter an afternoon slump. Caffeine is effective at reducing grogginess because it blocks adenosine receptors. Adenosine is a chemical that builds up in our bodies throughout the day to ultimately promote sleepiness at night, but caffeine blocks it from working on your brain cells.

Over time, your body produces more adenosine to counter these effects, so you may notice that if you’ve been drinking coffee for a while, you need more to feel the same energizing effect.

Most people can consume up to 400 milligrams (mg) of caffeine per day without issue. For reference, an eight-ounce cup of coffee typically contains 80–100 mg of caffeine, but the caffeine content can vary based on how it’s brewed. If you’re consuming other caffeine-containing foods and beverages, like energy drinks, the manufacturer may include the caffeine content on the label. 

A 12-ounce can of caffeinated soda usually contains 30–40 mg of caffeine, and an eight-ounce cup of green or black tea typically has 30–50 mg. Even decaffeinated coffee has some caffeine—about two to 15 mg in an eight-ounce cup—but it’s far less than regular coffee. Energy drinks are higher in caffeine, with 100–300 mg of caffeine per serving depending on the drink. 

If you consume more than 400 mg of caffeine per day, it’s more likely you’ll experience health issues like restlessness, insomnia, and anxiety. It’s also more likely you’ll become dependent on caffeine and experience withdrawal symptoms like headaches, drowsiness, and irritability if you start cutting back on your caffeine intake.

It’s always best to consult with your healthcare providers about your caffeine consumption and whether you need to take special precautions around caffeine. However, certain groups are at higher risk of experiencing negative effects from caffeine intake and should consume minimal or no caffeine. These include:

• People with acid reflux or gastroesophageal reflux disease (GERD). Caffeine increases the release of acid in your stomach, which can cause heartburn. People who have preexisting reflux issues may find caffeine to be a trigger for their symptoms.
• Pregnant individuals. It’s safe to consume up to 200 mg of caffeine per day during pregnancy. However, some studies have found consuming over 400 mg per day is associated with lower birth weights and an increased risk of miscarriage.
• People who are breastfeeding. A small amount of the caffeine you consume is passed on to your infant while breastfeeding, so consult with your healthcare provider as to whether you should limit caffeine while breastfeeding. 
• People taking certain medications. Caffeine may interact with certain stimulants, some antibiotics, asthma medications, and heart medications. 
• Children or teens. Regular caffeine consumption can have a negative impact on growth and development in children and adolescents. Young people can also be especially sensitive to the effects of caffeine.

Because of the potential side effects of caffeine, people with preexisting health issues that cause symptoms similar to those of excessive caffeine intake may need to limit their caffeine to prevent worsening their symptoms. These conditions include:

• Migraines or chronic headaches. When consumed in excess, caffeine can cause headaches. Caffeine withdrawal can also lead to headaches; however, caffeine is also found in some migraine medications.  
• Sleeping issues. Since caffeine is a stimulant, consuming it in excess can cause sleep issues. Those with preexisting sleep issues may find consuming caffeine, particularly within a few hours of going to bed, worsens sleep troubles. 
• Severe anxiety. Excess caffeine can cause jitters, restlessness, and anxiety. People with anxiety may find drinking caffeine heightens their symptoms.
• Heart issues. While caffeine may help with heart health, it can also cause rapid heart rate and increase blood pressure in the short term. Talk to your cardiologist about appropriate caffeine use if you have a heart condition.

That morning cup of joe may be doing more for your health than you realize. Moderate caffeine consumption is linked with a variety of health benefits including better brain health, reduced risk of heart failure, and anti-inflammatory effects.

However, consuming too much caffeine can lead to anxiety, restlessness, headaches, among other side effects. Speak with a trusted healthcare provider if you’re unsure about how much caffeine is safe for you.