What is Caffeine? & How does caffeine work?

Caffeine and Health

Author: Fathima Sible D Souza

What is Caffeine?

Caffeine is a naturally occurring chemical found in coffee, cacao, kola nuts, tea leaves, and 60 other products. For many of us, there is nothing better than waking up to a cup of coffee or tea, possibly because it gives us a burst of energy and alertness. The reason for this is that coffee or tea contains a central nervous system stimulant called caffeine. Evidence suggests that moderate coffee consumption can have both benefits and risks, despite ongoing debates about the health effects and drawbacks of caffeine.

How does caffeine work? The mechanism behind it.

Caffeine primarily attaches to the adenosine receptors present in the brain. There are four types of adenosine receptors in the brain, namely A1, A2a, A2b, and A3. These receptors are soluble in both lipids and water, which makes it easy for caffeine to enter the brain and bind to all four of these receptors, thereby blocking them. A2a is the major receptor the blockage of which induces the refreshing feeling of caffeine in the body.

Adenosine receptors are located throughout the body. Their presence isn’t limited to CNS. They cover a wide range of autonomic, enteric, and other organ system pathways. Blocking adenosine receptors results in the release of catecholamines like adrenaline and noradrenaline, which can increase heart rate and cause overall arousal of the body.

Absorption, Metabolism, Excretion of Caffeine

Humans can absorb nearly 99% of the caffeine in their system within 45 minutes. When caffeine is consumed in fluid forms such as coffee or tea, it is quickly absorbed from the gastrointestinal tract. However, if caffeine is consumed in forms like candy, gum, or other preparations that facilitate absorption through the oral mucosa, the absorption can be even faster. After the oral intake, peak plasma concentration is reached within about 15-20 minutes.

Caffeine undergoes metabolism in the liver through hepatic microsomal enzymes. This process results in the production of dimethylxanthine compounds, which can be either theophylline, theobromine, or paraxanthine (70-80%). Each of these metabolites has a distinct physiological function in the body. Eventually, the metabolites are excreted in the urine.

The metabolism varies from person to person depending on several factors

• Smokers are known to metabolize caffeine pretty fast compared to nonsmokers; half-life reduces to 50% in the case of smokers
• Pregnant ladies particularly the ones in their latter trimester would exhibit a longer half-life of up to 15 hours
• Newborns have a longer half-life of up to 8 hours
• People with liver disease also experience longer half-lives due to decreased enzyme activity.

Some sources of caffeine

1. Coffee
2. Chocolate especially Dark chocolate
3. Green tea
4. Chewing gum/ Coffee flavoured candy
5. Soft drinks/ Energy drinks

Caffeine and health

1. Anxiety and jitters: Individual reactions vary differently for moderate to high coffee consumption. Higher doses of caffeine can worsen the feeling of anxiousness and nervousness causing jitters.
2. Insomnia: Caffeine has the power to block adenosine a chemical responsible for prolonged awakeness and alertness. Therefore Caffeine can make it harder to fall asleep reducing the amount of time spent in deep sleep.
3. Increased Heart rate & Blood pressure: Caffeine intake can stimulate the release of catecholamines, such as adrenaline and noradrenaline, which can lead to an increase in heart rate and blood pressure. This can lead to palpitations or atrial fibrillation in some individuals and usually increases heart rate by an average of 3 beats per minute.
4. Stomach issues: Caffeine exacerbates the symptoms of acid reflux, heartburn, and gastrointestinal pain by increasing the acid secretion in the stomach.
5. Dependency and caffeine withdrawal: Just like many other medications caffeine also has the potential to develop dependency and tolerance leading to increased consumption of caffeine over time. This can cause fatigue, sweating, anxiety, muscle pain.
6. Caffeine in the bones: Caffeine consumption decreases the absorption of calcium eventually leading to osteoporosis, a condition where bones turn fragile and more easily breakable.
7. Increased urination: Caffeine acts as a diuretic, which means that it increases the production and excretion of urine. If caffeine intake is not accompanied by proper fluid intake, this can lead to bladder instability.
8. Risks during pregnancy: Consuming high amounts of caffeine during pregnancy has been linked to an increased risk of miscarriages and other adverse pregnancy outcomes. As a result, pregnant individuals are advised to limit their coffee intake to a maximum of 200mg per day.

Decaffeinated coffee

A decaffeinated coffee is one that has its coffee contents removed from the coffee beans. These are preferred by the ones who are sensitive to caffeine or the ones who want give the coffee to their children. Although the name suggests otherwise, decaffeinated coffee do contain very small amount of caffeine, probably much lower than regular coffee. A cup of decaffeinated coffee contains around 2-15mg of caffeine, this measure depends upon the cup of coffee.

Recommended caffeine intake

The FDA recommends that an adult in good health should not consume more than 400mg of caffeine per day, which is equivalent to drinking 4-5 cups of coffee. It is essential to keep in mind that people’s response and tolerance to caffeine may vary, and this is also influenced by how quickly their body can process caffeine.

Caffeine overdose

The FDA has warned that consuming over 1200mg of caffeine can lead to toxic effects like seizures. Consuming 1 gram of caffeine can result in symptoms such as restlessness, irritability, nervousness, palpitations, etc. However, it is rare for caffeine toxicity to occur since it requires a very high intake of caffeine within a few hours.

In dietary supplements that has bulk servings in powdered or liquid forms, it becomes difficult for an individual to measure out the right amount. This is an example of caffeine overdose.

Conclusion

Caffeine a natural chemical deserves our thoughtful consideration. It can play a valuable part in health by proper awareness. Where consuming more than recommended amounts is associated with lots of side effects, consumption in limited amounts has its benefits. By understanding our body’s response, sticking to the limited consumption of caffeine and being aware of how caffeine play a pivotal role in overall well-being plays a key in understanding the good bad effects of caffeine. So the next time when you reach for that extra cup of coffee or energy drink, wait for a sec and reconsider. Your body will thank you in the long run.

 References:

• Evans J, Richards JR, Battisti AS. Caffeine. StatPearls [Internet]. StatPearls Publishing; 2024 Jan- Available from: https://www.ncbi.nlm.nih.gov/books/NBK430685/
• Institute of Medicine (US) Committee on Military Nutrition Research. Caffeine for the Sustainment of Mental Task Performance: Formulations for Military Operations. Washington (DC): National Academies Press (US); 2001. 2, Pharmacology of Caffeine. Available from: https://www.ncbi.nlm.nih.gov/books/NBK223808/
• Spilling the beans: how much caffeine is too much? Silver Spring (MD): U.S. Food and Drug Administration; 09-07-23. Available from: https://www.fda.gov/consumers/consumer-updates/spilling-beans-how-much-caffeine-too-much
• Schellack G. Caffeine: the” good”, the” bad” and the” ugly”. Professional Nursing Today. 2012 Mar 1;16(2):10-4.