Everything You Need to Know About Caffeine

Caffeine is a chemical compound. It is considered a drug, though it is freely available and not regulated. Caffeine naturally occurs in many plants, including coffee and cocoa beans, and tea leaves. It is also used in over-the-counter (OTC) and prescription medications. 

While the origin of caffeine's medicinal use is not totally known, research shows that the practice of consuming coffee and tea regularly is somewhat recent, from a historical perspective. Coffee use became widespread in the 15th and 16th centuries, and in Europe, during the 18th and 19th centuries.

As for tea, it became popular during the Ming Dynasty in China (14th through 17th centuries) and in the 18th century in Britain.

Caffeine's medicinal purposes go back much further than its modern use as a stimulant. This article will discuss what caffeine is, its potential benefits, side effects, and safety concerns.

Woman holding a cup of coffee

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What Is Caffeine?

In its most basic form, caffeine is a chemical compound. Its scientific name is 1,3,7-Trimethylpurine-2,6-dione. Caffeine is naturally found in more than 60 plants. It is commonly added to other substances like medicines, drinks, and foods (like energy drinks and snacks). 

What Caffeine Does

Caffeine is a stimulant. It acts on the central nervous system. Its role as a stimulant is why you feel alert and a boost of energy when you consume caffeine. 

Although caffeine may be most commonly used for its effect on alertness, it does have other effects on the body. These effects are generally the less desirable ones and act as a reminder that caffeine is a drug. 

In addition to increasing alertness, caffeine also:

  • Acts as a diuretic, which means that it will make your body get rid of more water and salt; this is why you often need to pee more when drinking caffeinated beverages like coffee and tea.
  • Causes more acid to be released in the stomach, which may make you have heartburn.
  • Increases your blood pressure.

Foods and Drinks That Contain Caffeine

As caffeine is naturally occurring in many plants, it can be commonly found in several foods and drinks. The most common is coffee and tea. Tea is a general term these days assigned to several herbal drinks, though tea is really just referring to green and black tea, both of which contain caffeine.

Common caffeine-containing drinks include:

  • Coffee
  • Espresso
  • Tea (green, black, and oolong)
  • Yerba mate
  • Energy and sports drinks, like those that include guarana (a seed from a South American plant)
  • Soda, like cola

Common foods with caffeine include:

  • Chocolate and chocolate-flavored foods (cacao pods being the caffeine source)
  • Foods with coffee in them, like tiramisu, coffee ice cream, and even some pastries
  • Kola nuts, which are native to tropical Africa
  • Energy snacks, like gels for sports activities
  • Gum

Other Uses

Caffeine is also used for its stimulating effects in other forms. Caffeine is commonly added to:

  • OTC medications like cold medicines, to fight off drowsiness
  • Pain medications, since caffeine has been shown to improve their effectiveness
  • Recreational drugs, like meth and cocaine
  • Sports performance drinks and supplements

Health Benefits

Caffeine does have some health benefits on the brain and body including:

Sharper Brain Function

It is no secret that a lot of people use coffee to focus and get work done. This is because the caffeine in coffee has stimulatory effects that can have positive effects on brain function. Research has shown that caffeine can make you more alert and help you concentrate. Too much caffeine, though, and sleep disturbances may decrease the positive benefits of caffeine’s impact on the brain.

Influences Metabolism

Caffeine affects the processes by which fats are generated and broken down in the body. Research has suggested that caffeine may influence certain factors that can help improve fat metabolism, but more research is needed to understand the exact mechanism in humans.

Improved Exercise Performance

Caffeine is commonly known to enhance exercise performance, and it seems that this is the case for trained and untrained individuals. The type of exercise that caffeine seems to have the most beneficial effect on is aerobic exercise, though it differs between individuals.

How much caffeine needs to be taken to benefit from its exercise-enhancing effects depends on body weight. According to the International Society of Sports Nutrition, 3-6 milligrams per kilogram (mg/kg) of bodyweight seems to be the dose at which people see the benefit, and it is generally taken one hour before exercise.

Diabetes and Heart Disease

Coffee and tea consumption has been associated with decreased risk of metabolic syndrome. Metabolic syndrome is a health condition that increases the risk of health issues like diabetes and heart disease.

Researchers note that the benefits are likely due to the antioxidant polyphenols found in coffee and tea rather than the caffeine itself.

Other Benefits

Related to brain function benefits, caffeine may be able to improve mood. Combined with the usual suspects of improved mood like good sleep and exercise, caffeine consumption can be beneficial for mental health. There’s also the fact that caffeine-containing drinks and foods like coffee, tea, and chocolate are tasty and pleasurable to eat and drink, which shouldn’t be discounted in terms of well-being.

Caffeine Side Effects and Safety

Despite its health benefits, caffeine can have negative side effects. This is where it is helpful to remember that caffeine is classified as a drug and should be treated as such when using it outside the recommended doses or uses. 

Some common side effects of too much caffeine include:

  • Shakiness and inability to sit still
  • Insomnia or sleep disturbances 
  • Headache
  • Stomach ache or heartburn
  • Dizziness
  • Increased heart rate
  • Dehydration
  • Anxiety
  • Dependency, which means you need more to get the same effect


Dosing recommendations are tricky, as some people are more sensitive to caffeine than others. Also, some people will metabolize caffeine faster, which means they may feel the effects sooner and therefore won’t need as much to get going. In general, the FDA recommends no more than 400 milligrams of caffeine a day, which is about the equivalent of four of five cups of coffee.

It is important to remember that small doses of caffeine can still contain high concentrations. For example, one teaspoon of pure powdered caffeine contains the same amount of 28 cups of coffee; this can be a toxic amount. Pure and highly concentrated caffeine products are a health risk. 


As with any substance that is consumed, caffeine will interact with other substances in the body. For example, caffeine can make it harder for your body to absorb calcium if they are taken close together. Some medications may make you more sensitive to caffeine, as well as some conditions. Pregnancy is a health condition in which you’d want to consult your healthcare provider about caffeine consumption.


Caffeine is a chemical compound that many people consume every day. It is most commonly consumed in coffee and tea, though it can also be consumed through other foods and drinks, certain medications, and even recreational drugs. Caffeine does have health benefits, but like with any drug, excessively high doses can pose health risks. For most people, the everyday use of caffeine through coffee or tea is just fine.

A Word From Verywell

Caffeine has become an everyday occurrence and perceived necessity for many people who rely on a cup of coffee or tea to start their day. However, there are concerns about too much caffeine with the abundance of energy drinks and other highly caffeinated substances readily available.

Knowing how much caffeine is too much can be tricky. Generally speaking, you can look to negative side effects to tell you when it’s too much. For most, getting caffeine through coffee may have mental and physical benefits, in addition to being one of life’s simple pleasures.

Frequently Asked Questions

  • How much caffeine does coffee have?

    An 8-ounce cup of coffee, which is one cup as measured with a measuring cup, contains 95-200 milligrams of caffeine.

  • How long do caffeine effects last?

    Generally, it takes your body four to six hours to break down half of the caffeine you consumed. This is why you may hear the “half-life” of coffee is around four to six hours. Thus, caffeine's effects, such as alertness, may last at least that long. It varies by individual.

  • Is naturally sourced caffeine bad for you?

    Most of the time, caffeine consumed from natural sources like tea and coffee is fine for your health, when consumed in normal amounts. However, if you drink too much coffee or tea, you may experience negative health effects.

  • How much caffeine can you have if pregnant?

    This is a question for the pregnant person’s healthcare provider. The FDA recommends that anyone who is pregnant, trying to become pregnant, or breastfeeding talks to their healthcare provider about whether they should limit their caffeine intake.

  • Is caffeine a drug?

    Yes. Caffeine is a stimulant drug of the methylxanthine class. Unlike many other drugs, caffeine is readily available, such as in caffeine-containing drinks and foods.

9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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