If your morning ritual consists of making a grab for a takeout tea or coffee to get your much-needed caffeine fix, you are not alone. Caffeine is used by the masses on a daily basis to increase wakefulness, alleviate fatigue, and improve concentration and focus.
Caffeine is the most commonly used drug in the world. Although the consumption of low to moderate doses of caffeine is generally safe and has many proven health benefits, long-term excessive caffeine intake is causing quite a stir as a potential risk factor in certain health problems.
Contents of this article:
- What is caffeine?
- Where is caffeine found?
- What is caffeine used for?
- Caffeine content
- How does caffeine affect the body?
- How does caffeine work?
- Caffeine side effects
- Children and adolescents
- Caffeine tolerance
- What is caffeine dependence and withdrawal?
- Does caffeine have any health benefits?
- What are the risks of consuming caffeine?
- Caffeine sensitivity
- Caffeine overdose
You will also see introductions at the end of some sections to any recent developments that have been covered by MNT's news stories. Also look out for links to information about related conditions.
Fast facts on caffeine
Here are some key points about caffeine. More detail and supporting information is in the main article.18
- At least 68 million Americans drink three cups of coffee every day.
- Some 30 million Americans drink five or more cups of coffee every day.
- Over 21 million Americans drink six or more cups of coffee every day.
- It is believed that some 3 out of 4 regular caffeine users are "addicted" to the substance.
- Consuming as little as 200 mg of caffeine a day can lead to addiction and altered chemistry in the brain in some people.
- Around 5 grams of caffeine can be fatal. This is the equivalent of some 30-40 cups of regular coffee.
- Some 50% of people who quit using caffeine experience severe headaches that typically last between 2-9 days.
- Caffeine is found naturally in over 60 plants grown worldwide.
- Energy drinks often contain high levels of caffeine: Red Bull is the most popular energy drink in the US, with Monster a close second.
- Some 5% of adults consume 5-7 energy drinks every month. Over 2% of adults consume at least 10 energy drinks every month.
What is caffeine?
In the US, more than 90% of adults use caffeine regularly, with an average consumption of more than 200 mg of caffeine per day - more caffeine than in two 6 ounce cups of coffee or five 12 ounce cans of soft drinks.
More than 90% of adults in the US use caffeine regularly with an average consumption of more than 200 mg per day.
Caffeine is a bitter, white crystalline xanthine alkaloid - a term used for substances produced as end products of nitrogen metabolism in some plants. The stimulant chemical is also known as coffeine, theine, mateine, guaranine, or methyltheobromine.14
Caffeine belongs to the family of heterocyclic compounds known as purines and is a member of a group of naturally occurring substances called methylxanthines. It has the systematic name 3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione, also known as 1,3,7-trimethylxanthine, and 1,3,7-trimethyl-2,6-dioxopurine.
The chemical formula is C8H10N4O2. Caffeine has a molar mass of 194.19 grams (6.85 ounces). It is soluble in water and many organic solvents, has a melting point of 235-238 °C and it appears in pure form as white crystals. Caffeine can be prepared by extraction from natural sources or synthesis from uric acid.
Where is caffeine found?
Caffeine occurs naturally in the leaves, seeds or fruit of more than 60 plant species, including:
- Coffee beans - seed
- Tea leaves - leaves, bud
- Kola nuts - seed
- Cacao beans - seed
- Guarana - seed
- Yerba mate - leaf
- Yoco - bark.
Caffeine acts as a natural pesticide for the plants, and paralyzes and kills insects that attempt to feed on the plants. The German chemist Friedrich Ferdinand Runge first isolated the molecule in 1819.14
Man-made caffeine is sometimes added to foods, drinks, and medicines.3
What is caffeine used for?
The Food and Drug Administration (FDA) says that caffeine is both a drug and a food additive. Caffeine is used in both prescription and over-the-counter medicines to treat tiredness, drowsiness and to improve the effect of some pain relievers.3
Coffee, tea and chocolate can all contain caffeine.
When purified, caffeine is an intensely bitter white powder. It is added to enhance colas and other soft drinks so that they impart a pleasing bitter note. However, caffeine is also considered to be an addictive stimulant. In humans, caffeine stimulates the central nervous system, increases heart rate and respiration, has psychotropic (mood-altering) properties and acts as a mild diuretic.13
Sources of caffeine include:
- Coffee and tea
- Sports beverages
- Chewing gum
- Energy drinks.
Caffeine belongs to the group of medicines called central nervous system (CNS) stimulants. In conventional foods, caffeine may help restore mental alertness when unusual tiredness, weakness or drowsiness occurs. 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.12
Sources of caffeine in dietary supplements include:
- Energy shots
- Energy drinks.
Caffeine is also used in combination with ergotamine, for the treatment of migraine and cluster headaches, or with certain pain relievers, such as aspirin and acetaminophen. Caffeine helps to increase the effectiveness of these medicines.12
Caffeine can also be used:
- To treat breathing problems in premature babies
- For postoperative infant apnea - breathing problems after surgery in young babies
- For psychiatric disorders requiring electroconvulsive or shock therapy (ECT).
Caffeine no longer only features in tea, coffee and chocolate. Caffeine is regularly added to gum, jelly beans, waffles, water and syrup to name a few.4
In response to the trend of "added caffeine" in a growing number of products, the FDA is investigating the safety of caffeine in foods and particularly its effects on children and adolescents.4
"Energy drinks" with caffeine are considered by some to be aggressively marketed, particularly to young people, with additional products appearing on the market, from "psyched up" oatmeal to "wired" waffles.
Caffeine is even being added to marshmallows, sunflower seeds and other snacks for its stimulant effect.4
For healthy adults, the FDA has cited 400 milligrams of caffeine a day - about 4 or 5 cups of coffee a day - as an amount not associated with dangerous or negative side effects.
The FDA has not set an amount for children, but the American Academy of Pediatrics discourages the consumption of caffeine and other stimulants by children and adolescents.4
The amount of caffeine included in some common foods and beverages are:19
For healthy adults, about 4 or 5 cups of coffee a day is an amount not associated with dangerous or negative side effects.
- Coffee, brewed - 40 to 180 milligrams (mg) per cup
- Coffee, instant - 30 to 120 mg per cup
- Coffee, decaffeinated - 3 to 5 mg per cup
- Tea, brewed American - 20 to 90 mg per cup
- Tea, brewed imported - 25 to 110 mg per cup
- Tea, instant - 28 mg per cup
- Tea, canned iced - 22 to 36 mg per 12 ounces
- Caffeine-containing cola and other soft drinks - 36 to 90 mg per 12 ounces
- Cola and other soft drinks, decaffeinated - 0 mg per 12 ounces
- Cocoa - 4 mg per cup
- Chocolate, milk - 3 to 6 mg per ounce
- Chocolate, bittersweet - 25 mg per ounce.
On the next page we look at how caffeine affects the body and the benefits of drinking it. On the final page we discuss the health risks associated with caffeine consumption, caffeine sensitivity and caffeine overdose.