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What Is Caffeine? What You Should Know

What Is Caffeine What You Should Know

Each day, billions of people rely on caffeine to wake up, or to get through that night shift or an afternoon slump.

In fact, this natural stimulant is one of the most commonly used ingredients in the world.

Caffeine is a chemical found in coffee, tea, cola, guarana, mate, and other products.

Caffeine is most commonly used to improve mental alertness, but it has many other uses. Caffeine is used by mouth or rectally in combination with painkillers (such as aspirin and acetaminophen) and a chemical called ergotamine for treating migraine headaches. It is also used with painkillers for simple headaches and preventing and treating headaches after epidural anesthesia.

Some people use caffeine by mouth for asthma, gallbladder disease, attention deficit-hyperactivity disorder (ADHD), and many other conditions, but there is no good scientific evidence to support most of these uses.

Caffeine is one of the most commonly used stimulants among athletes. Taking caffeine, within limits, is allowed by the National Collegiate Athletic Association (NCAA). Urine concentrations over 15 mcg/mL are prohibited. It takes most people about 8 cups of coffee providing 100 mg/cup to reach this urine concentration.

Some caffeine products are sold in very concentrated or pure forms. These products are a health concern. People can easily use these products in doses that are much too high by mistake. This can lead to death. As of 2018, the U.S. Food and Drug Administration (FDA) considers it unlawful for these products to be sold to consumers in bulk. 

After you consume caffeine, it’s absorbed into your bloodstream, where levels peak in as little as 15 minutes; later, the liver takes over in eliminating caffeine.

What Is Caffeine?

There are few people who are not aware of the stimulating effect that caffeine provides. We have a choice and choose caffeinated beverages for a reason. Caffeine is considered the most commonly used psychoactive drug in the world. A majority of adults consume it on a daily basis, and research is being done on its health benefits and consequences.

We may love our caffeine, but what exactly is it? Caffeine is the common name for 1,3,7-trimethylxanthine. When purified, caffeine produces an intensely bitter white powder that provides a distinctive taste in soft drinks. The word “caffeine” came from the German word kaffee and the French word café, each meaning coffee.

After ingesting caffeine, it is completely absorbed within 30 to 45 minutes, and its effects substantially diminish within about three hours. It is eventually excreted so there is no accumulation in the body. Caffeine has been shown to affect mood, stamina, the cerebral vascular system, and gastric and colonic activity. But caffeine may not be for everyone. This article will discuss the health benefits and consequences of caffeine.

While you may pour yourself endless cups of coffee to survive the morning, the Mayo Clinic notes that drinking 400 milligrams (mg) of caffeine a day is safe for healthy adults. They note that this is the equivalent to four cups of coffee per day, but that all depends on where your coffee comes from. For instance:

  • Standard brewed 8-ounce (oz) cup of coffee: 95 mg caffeine
  • Standard instant 8-oz cup of coffee: 62 mg caffeine
  • Starbucks blonde roast, 8 oz (short): 180 mg caffeine
  • Starbucks blonde roast, 16 oz (grande): 360 mg caffeine
  • Starbucks iced coffee, 16 oz (grande): 190 mg caffeine
  • Coffee brewed from Keurig, 8-oz cup: between 75 and 150 mg caffeine, depending in part on roasting strength

As you can see, to stay within the safe limit, you should investigate just how much caffeine your specific brew contains. And, if you’re looking to cut down on caffeine, the first step is to reduce your coffee intake, as it’s the most widely consumed source of caffeine, research shows.

Where Caffeine Is Found

Though the chatter is always on coffee, caffeine is found in many other sources, including:

Tea While most herbal teas (like chamomile) are caffeine-free, others contain varying amounts. For instance, green contains 25 to 29 mg per cup, while black racks up more, with 25 to 48 mg per cup.

Decaf Decaf coffees and teas will have minimal amounts of caffeine, about 2 to 5 mg.

Chocolate Cocoa naturally contains caffeine. One oz of dark chocolate offers 12 mg.

Chocolate Ice Cream This treat also has minimal amounts of caffeine, about 4 mg per 1-cup serving.

Energy Drinks A 8.4-oz can of Red Bull contains 80 mg, while a 16-oz can of Monster contains 160 mg.

Cola One 16-oz can has 44 mg.

Caffeinated Water In this instance, caffeine is added to the mix. One variety, the apple-pear flavor by Hint, contains 60 mg of caffeine per 16-oz bottle.

Migraine Medication Some over-the-counter migraine drugs contain a combo of pain relievers acetaminophen, aspirin, and caffeine (65 mg per tablet). That said, too much caffeine can actually causeheadaches, so watch the amount you consume from other sources.


The Food and Drug Administration (FDA) consider caffeine to be both a drug and a food additive. They recommend a maximum intake of 400 mg a day.

In prescription and over-the-counter (OTC) medicines, caffeine is used to treat tiredness and drowsiness, and to improve the effect of some pain relievers.

It belongs to a group of medicines called central nervous system (CNS) stimulants.

Foods containing caffeine can help restore mental alertness.

Caffeine’s use as an alertness aid should only be occasional. It is not intended to replace sleep and should not regularly be used for this purpose.

In the United States (U.S.), more than 90 percent of adults use caffeine regularly, with an average consumption of more than 200 milligrams of caffeine per day. This is more caffeine than in two 6-ounce cups of coffee or five 12-ounce cans of soft drink.

Potential Health Benefits of Caffeine

May Improve Mood and Brain Function

Caffeine has the ability to block the brain-signaling molecule adenosine.

This causes a relative increase in other signaling molecules, such as dopamine and norepinephrine.

This change in brain messaging is thought to benefit your mood and brain function.

One review reports that after participants ingested 37.5–450 mg of caffeine, they had improved alertness, short-term recall, and reaction time.

In addition, a study linked drinking 2–3 cups of caffeinated coffee (providing about 200–300 mg caffeine) per day to a 45% lower risk of suicide.

Another study reported a 13% lower risk of depression in caffeine consumers.

When it comes to mood, more caffeine isn’t necessarily better.

A study found that a second cup of coffee produced no further benefits unless it was consumed at least 8 hours after the first cup.

Drinking between 3–5 cups of coffee per day or more than 3 cups of tea per day may also reduce the risk of brain diseases such as Alzheimer’s and Parkinson’s by 28–60%.

It’s important to note that coffee and tea contain other bioactive compounds (besides caffeine) that may also be beneficial.

Alzheimer’s and Parkinson’s Disease

Research has found that lifelong caffeine consumption may reduce the risk of developing Alzheimer’s disease.

Studies have also reported that people with a higher coffee consumption have a lower risk of Parkinson’s disease.

Safeguard Your Heart

In a study that looked at 185,855 people ages 45 to 75 — including African-Americans, Native Hawaiians, Japanese-Americans, Latinos, and whites — coffee drinkers who sipped two to three cups a day saw their risk of death due to conditions like heart disease and stroke drop by 18 percent compared with non-java drinkers, noted a study published in August 2017 in the journal Annals of Internal Medicine.

May Boost Metabolism and Fat Burning

Because of its ability to stimulate the central nervous system, caffeine may increase metabolism by up to 11% and fat burning by up to 13% .

Practically speaking, consuming 300 mg of caffeine per day may allow you to burn an extra 79 calories daily.

This amount may seem small, but it’s similar to the calorie excess responsible for the average yearly weight gain of 2.2 pounds (1 kg) in Americans.

However, a 12-year study on caffeine and weight gain noted that the participants who drank the most coffee were, on average, only 0.8–1.1 pounds (0.4–0.5 kg) lighter at the end of the study.

Liver and Colon

It has been suggested that caffeine enemas may help prepare the colon for an endoscopy or colonoscopy by supporting the excretion of bile through the colon wall.

Proponents claim that a caffeine enema increases the levels of glutathione, an antioxidant, and so it supports the natural processes of detoxification in the liver.

However, there is little evidence to support this theory.

Coffee consumption may help decrease the risk of cirrhosis and slow the rate of disease progression in hepatitis C infection. Observational studies have found that coffee may have protective benefits for people with hepatocellular cancer.

Protect Against Cancer

A review published in November 2017 in the journal BMJ looked at 201 meta-analyses and found that drinking coffee was associated with an 18 percent lower risk of cancer. The authors recommend sticking to three to four cups of coffee a day. Specifically, they found that coffee can decrease the odds of prostate cancer, endometrial cancer, melanoma, nonmelanoma skin cancer, and liver cancer. Why? Coffee is rich in disease-fighting and anti-inflammatory antioxidants, and caffeine also has antioxidant properties.

May Enhance Exercise Performance

When it comes to exercise, caffeine may increase the use of fat as fuel.

This is beneficial because it can help the glucose stored in muscles last longer, potentially delaying the time it takes your muscles to reach exhaustion.

Caffeine may also improve muscle contractions and increase tolerance to fatigue.

Researchers observed that doses of 2.3 mg per pound (5 mg per kg) of body weight improved endurance performance by up to 5% when consumed 1 hour before exercise.

Doses as low as 1.4 mg per pound (3 mg per kg) of body weight may be sufficient to reap the benefits (23).

What’s more, studies report similar benefits in team sports, high intensity workouts, and resistance exercises (23, 24).

Finally, it may also reduce perceived exertion during exercise by up to 5.6%, which can make workouts feel easier.

Eyelid Spasm

There is some evidence that caffeine may help protect people from an eye disorder known as blepharospasm.

This condition, caused by abnormal brain function, makes people blink incessantly and can leave them functionally blind.

Prevent Diabetes

If you drink coffee here and there, you may consider boosting your brew. In a study published in April 2014 in the journal Diabetologia, men and women who increased their coffee consumption by 1.5 cups a day benefited from a 11 percent lower risk of type 2 diabetes over a four-year period compared with those who didn’t start sipping more. On the other hand, those who dropped two cups a day had a 17 percent higher risk of the disease.

While that sounds promising, senior author Frank Hu noted that other lifestyle measures are likely more important than coffee (or caffeine) alone. “But coffee is only one of many factors that influence diabetes risk. More importantly, individuals should watch their weight and be physically active,” he said in a press release.

Skin Cancer

Some scientists have suggested that caffeine may guard against certain skin cancers.

One team found that caffeine applied directly to the skin of mice helped prevent damaging ultraviolet (UV) light from causing skin cancer.

Others have linked the consumption of three cups of caffeinated coffee a day with a 21 percent lower risk of developing basal cell carcinoma in women, and a 10 percent lower risk in men, compared with drinking less than one cup per month.

Kidney Stones

A study of 217,883 participants analyzed the association between caffeine intake and the risk of developing kidney stones.

Those who consumed more caffeine had a lower risk of developing kidney stones.

Delay Dementia

While research isn’t conclusive that coffee or caffeine may prevent Alzheimer’s, it may help prevent those suffering from mild cognitive impairment from progressing to dementia, suggests a study published in 2012 in the Journal of Alzheimer’s Disease. (25) Those who developed dementia had 51 percent lower caffeine levels in their blood compared with those with MCI whose disease didn’t advance. Caffeine may interact with a component in coffee to increase levels of a growth factor that stymies Alzheimer’s progression, the authors note in a press release. Three cups of coffee is the ideal amount, they said.

Mouth, Throat, and Other Cancers

In a study of 968,432 men and women, participants who drank than 4 cups of coffee a day had a 49-percent lower risk of death from oral cancer, compared with those who drank no coffee at all or only an occasional cup.

Other possible cancer-related benefits include:

  • a lower risk of endometrial cancer
  • a reduced risk of prostate cancer
  • protection against head and neck cancer
  • protection against the recurrence of breast cancer


Data for 34,670 women in Sweden without a history of cardiovascular disease indicated that women who drank more than one cup of coffee per day had a 22 to 25-percent lower risk of stroke compared with women who drank less.

Low or no coffee drinking appeared to be linked to an increased risk of stroke.

Stave Off Depression

In one study, over 50,000 women who didn’t have depressive symptoms were followed for 10 years. Those who drank two to three cups of coffee a day had a 15 percent lower likelihood of suffering from depression compared with those who had less than a cup per week. The stimulant effect of caffeine may boost your sense of well-being and energy, the authors note. It may also play a role in releasing happy chemicals, like dopamine and serotonin.

Common Side Effects

Caffeine can improve alertness, but it can also lead to a number of unpleasant side effects, including:

  • Restlessness
  • Nervousness
  • Excitement
  • Insomnia
  • Flushed Face
  • Excessive urination
  • Gastrointestinal disturbances
  • Muscle twitching
  • Rambling speech
  • Tachycardia or cardiac arrhythmia
  • Periods of inexhaustibility
  • Difficulty relaxing

It was only recently that the World Health Organization took coffee off of its list of potentially carcinogenic foods, Harvard Health reports. That’s certainly good news.

But remember that moderation is key when it comes to caffeine. Certainly, if you’re drinking too much, short-term side effects can include migraines, insomnia, nervousness, irritability, restlessness, frequent urination, stomach upset, fast heartbeat, and muscle tremors, according to the Mayo Clinic. And, as they point out, everyone reacts to it differently. It’s important to learn how your body handles caffeine so that you can hit a sweet spot where it perks you up without causing problems.

If you want to sleep well at night, know your limit with how late you should be drinking it. It takes six hours for your body to eliminate half of the caffeine you drank. The risk is drinking it too late where it interferes with your sleep, then having to compensate the next day with more caffeine — it can be a difficult cycle to get out of. The thing is, caffeine can sap your sleep even if you drink it six hours before bed, research has shown.

Another concern: If you’re pregnant. While the thought used to be that caffeine was off limits for pregnant women, it’s now recommended that they keep their caffeine intake to a certain limit to help avoid complications like preterm birth or low birth weight. (While the World Health Organization recommends below under 300 mg per day, recommendations vary.) If you’re pregnant, the best course of action for you and your baby is to chat with your physician about how much (if any) caffeine is best to include in your diet.

And finally, if you have type 2 diabetes, that’s another time to check your caffeine intake. While it’s associated with a decreased risk for developing diabetes, it can be different story for people who already have the disease. Caffeine may impact insulin and increase or decrease blood sugar levels. It’s always a good idea to talk to your doctor to see what’s best for you given your individual health concerns.

Effects of Caffeine on Your Body

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