Caffeine, by any standard, is the most popular drug in the world, easily surpassing nicotine and alcohol. It is the only addictive psychoactive substance that has overcome disapproval and resistance and is freely available everywhere, uncontrolled, and sold without any regulation or license.

More than 85% of Americans consume significant amounts of this drug on a daily basis. In 2020, almost 10 million tons of coffee beans were consumed worldwide.

It is among the most widely studied drug and yet we know so little of it.

It forms a large component of tea, coffee, and cola, the three most widely consumed beverages in the world. Their universal appeal is primarily due to the stimulatory effect of caffeine. Herbal teas, however, contain no caffeine.

What is caffeine? What are its sources?

Pure caffeine is a highly toxic, bitter white powder readily soluble in boiling water. Regular caffeine, which we use is a central nervous system stimulant of the methylxanthine class, due to which it is mainly used to enhance cognition and increase alertness and concentration.

Caffeine occurs naturally in the fruit, leaves, and beans of more than 60 plants including:

  • Coffee beans
  • Tea leaves
  • Kola nuts, which are used to flavor soft drink colas
  • Cacao pods, which are used to make chocolate products
  • Guarana plants

There is also a synthetic variety, which is used in the production of some medicines, foods, and drinks.

Medicines in which synthetic form is used include some pain relievers, cold medicines, and over-the-counter medicines for alertness. It also forms an important ingredient of energy drinks and “energy-boosting” gums and snacks.

People mostly consume caffeine from beverages. The amount of its content in different products varies. For example,

  • An 8-ounce cup of coffee contains 95-200 mg
  • A 12-ounce can of cola has 35-45 mg
  • An 8-ounce energy drink will have 70-100 mg
  • One 8-ounce cup of black tea contains 14-60 mg
  • An 8-ounce cup of green tea contains between 30 and 50 mg.
  • One chocolate bar – 21 to 76 mg/100 gm

One ounce of liquid = about 30 ml

What does caffeine do to your body?

Caffeine is a central nervous system stimulant, which means it enhances activity in your brain and nervous system. It is rapidly absorbed by the body, and its short-term effects are usually experienced between 5 and 30 minutes after you have consumed it.

These include an increase in respiratory and heart rate, enhanced mental alertness, and physical energy. How long these effects last varies from person to person but they usually last up to 12 hours.

Caffeine is not safe when used in very high doses because it has negative effects. Larger doses can cause headaches, anxiety, and chest pain. It can cause irregular heartbeat and even death in very high doses. Consuming 10-14 grams at one time can be fatal.

How does it act in the body?

Caffeine acts as a stimulant in the body, primarily by blocking the function of the neurotransmitter, adenosine. When caffeine is absent, adenosine binds to its receptors (in the brain and nervous system). This makes you feel tired or less attentive. Caffeine blocks the action of adenosine on those same receptors. This leads to stimulation of the cells in the brain and spinal cord.

This stimulation can result in a feeling of increased energy levels, improved mood, and better focus. In some people, it can lead to anxiety, headaches, and sleep disturbances.

Caffeine also increases the release and circulation of hormones cortisol and adrenaline in the body. In appropriate doses, this makes you feel refreshed and more attentive. This is the primary reason, why it is so widely consumed across the globe.

Recommended intake amount

Excessive caffeine consumption has undesirable effects. You should therefore restrict your intake and stay well within the recommended limits, which are as follows:

  • Adults. The U.S. Food and Drug Administration recommends 400 milligrams (about 4 cups of brewed coffee) as a safe amount of caffeine for daily consumption in healthy adults. In the United States, on average, adults consume 135 mg of it daily, or the amount in 1.5 cups of coffee (8-ounce cup), which is well below the recommended limit.
  • Pregnant women. According to the American College of Obstetricians and Gynecologists, pregnant women should not consume more than 200 mg a day (about 2 cups of brewed coffee). Three cups of coffee per day can reduce the iron content in breast milk by one-third. Avoiding caffeine can improve the iron content of breast milk. Too much of it can dehydrate you and lower the production of your breast milk. Too much of it can affect your breastfeeding baby.
  • Children. The American Academy of Pediatrics suggests that children below 12 years of age should not consume any food or beverages containing caffeine.
  • Adolescents. Adolescents 12 years and older should not consume more than 100 mg of caffeine daily. This is the amount in an 8-ounce (240-mL) serving of coffee or three 12-ounce cans of cola soda.

After caffeine is consumed, it is quickly absorbed into the bloodstream from the stomach and intestines. It reaches its peak concentration in the bloodstream within 30 to 60 minutes. Most of it is removed from the body within 12 hours.

Smoking increases the rate at which caffeine is metabolized by half; alcohol reduces this rate further and oral contraceptives can decrease it by two-thirds.

Is it safe to consume caffeine daily?

According to The U.S. Food and Drug Administration, 400 milligrams is a safe amount of caffeine for healthy adults to consume daily. This amount is in about 4 cups of brewed coffee, 10 cans of cola, or 2 shots of energy drinks.

One Energy shot is about 50 milliliters or about two fluid ounces. Gulping down a shot allows the customer to get the energy boost quickly because it is in a more concentrated form.

Moderate consumption of coffee as per the above-prescribed limit is okay but it can bring both benefits and risks. However, high consumption of caffeine is not healthy and can have adverse effects on the body.

In addition, recently, there is a trend to add synthetic caffeine to drinks and snacks. The synthetic variety is made using chemicals that are harsh and not healthy to consume.

Who should avoid or limit caffeine?

You should limit or preferably avoid caffeine if you suffer from:

You should also avoid caffeinated beverages if you

  • Take certain medicines or supplements, such as stimulants, asthma medicines, and heart medicines.
  • Are a child or teen
  • Are pregnant, since caffeine passes through the placenta to your baby


How does caffeine give you energy?

  • Drinking caffeine gives you a boost of energy especially when you are feeling fatigued due to low-calorie intake.
  • It stimulates the sympathetic nervous system, as a result of which you feel hungry.
  • It reduces anxiety-related symptoms
  • Caffeine increases the breakdown of fat cells to be used for energy, thereby making you feel more energetic.

Which is the healthiest caffeine?

Besides other benefits, drinking tea or coffee improves your cardiovascular and metabolic health. It also reduces the risk of diabetes.

Caffeine consumption through coffee or tea is among the healthier options for its intake. However, these benefits do not accrue if cream or sugars are added to the beverages.

Where does caffeine come from?

Most of the caffeine in soft drinks is synthetic and comes from pharmaceutical factories in China. This synthetic form is also used to manufacture gum, dietary supplements, over-the-counter drugs, and personal hygiene products.

Naturally occurring caffeine occurs naturally in the fruit, leaves, and beans of more than 60 species of plants across the globe, of which sources such as the seeds of coffee beans, cacao beans, the leaves and buds of tea, and Kola nuts are well-known.

Other sources include the leaves of Yerba mate, the bark of Yoco, guarana berries, guayusa, and the yaupon holly. Caffeine is obtained from heated-up coffee beans.

Synthetic and natural caffeine are nearly indistinguishable, both being chemically identical. The synthetic variety is made from chemicals while the natural form is extracted from plant sources.