Health Benefits and Risks of Coffee

Whether you’re in a meeting, lecture, class or just working late, for a lot of people the first thing that springs to mind is coffee. As 125 million people are regular coffee drinkers, it is not surprising that it is one of the most consumed and exported products worldwide. But what is in a cup of coffee, and what does it do to our body to make us more awake, alert and energetic? Can caffeine actually be beneficial to our long-term health?

What’s In a Cup of Coffee?

Caffeine is a substance that is found in beverages such as energy drinks, tea, cola and obviously, coffee. It has a few different names, depending on its source – caffeine (coffee beans), theine (tea leaves), mateine (mate) or guaranine (guarana). It has the chemical formula of C8H10N4O2 and belongs a class of substances known as xanthines, some of which are found naturally in the human body. Its ability to interact with the central nervous system (CNS) is the reason for its popularity, promoting wakefulness by increased alertness and agitation1.

caffeine molecular structure molecule rings

Just a molecule of 1,3,7-trimethyl-2,3,6,7-tetrahydro-1H-purine-2,6-dione! Note the purine double ring structure that is characteristic of xanthines.

The stimulating effect of some plants had already been exploited more than 1000 years ago, though for a long time no one understood that caffeine was the source of its effects2. Let’s delve deeper into the biochemistry of caffeine and other xanthines.

Coffee in The Body

To arrive at the effects, we have to take a closer look at some metabolic pathways in the human body. Coffee that you drink enters your stomach where caffeine is introduced into the bloodstream, making its way to your liver. In the liver, caffeine molecules are picked up by an enzyme – cytochrome P450 – that helps to breaks it down into smaller components.

Related: Cytochrome P450 Enzymes: Meet the (Super)family

These components are known as metabolites, with the main metabolite being paraxanthine, though significant amounts of theophylline and theobromine are also produced. These are further converted into other molecules via various pathways; caffeine has a half-life of 3 to 10 hours1.

caffeine metabolism metabolic pathway cyp1a2 cyp450

Caffeine biochemistry: the primary end product is 1-methyluric acid (shown at to bottom of diagram); other side products are precursors to separate metabolism pathways.

Caffeine and paraxanthine act as ‘stimulants’ on the central nervous system, increasing the level of activity in the body. They do this by inhibiting adenosine receptors, that when activated promotes sleep and slows heart rate. Additionally, caffeine has been found to activate the release of adrenaline. This can lead to increased feelings of stress, alertness and agitation3.

Another metabolite – theophylline – promotes muscle relaxation and has a diuretic effect (makes you pee). Theobromine, on the other hand, has not been found to have any stimulating properties. However, it is said to be a mood enhancer and is also found in chocolate. If you ever wondered why you shouldn’t feed your pets chocolate, then you just got your answer: theobromine cannot be properly metabolized by animals like dogs and cats, so even small amounts put these animals at risk of being poisoned4.

Caffeine: Not So Simple

We’ve just learned that on one hand, caffeine can improve our mood while keeping us alert and awake. However, it can also increase stress and anxiety. During metabolization, toxic substances such as formaldehyde and hydrogen peroxide are also produced as side products. So, is coffee good or bad for you?

Although death by caffeine overdose is highly unlikely, coffee does have some side effects that could lead to a possibly fatal outcome5. Since the tightening of blood vessels is caused by inhibiting adenosine receptors, caffeine is associated with causing seizures and tachycardia (increased heart rate), which in at-risk individuals can lead to heart attacks or strokes6.

coffee beans many cup brown roast

The lethal dose of caffeine is 3 to 10 grams in a short period of time – depending on an individual’s age, gender, metabolism, etc. – which equates to drinking around 30 shots of single espresso (~100 mg caffeine) in one sitting7!

Other studies have concluded that the long-term health benefits of regular coffee-drinking (3 to 4 cups a day) outweigh the risks. There is data to support its protection against neurodegenerative diseases, asthma, liver disease and even cancer8,9.

Several compounds in coffee have anti-inflammatory and antioxidative properties; in some individuals, it can be used as an effective treatment for headaches and migraines. A study showed that drinking coffee reduces the mortality of HIV and hepatitis C virus patients. This is believed to stem from its anti-inflammatory effects10.

It is worth noting that although there is preliminary data supporting the health benefits of coffee consumption, very few clinical trials with the appropriate endpoints have actually been conducted. That being said, it is important not to be overreliant on coffee for its stimulant effects – after all, nothing beats a good night’s rest!


    1. Boutrel, B., & Koob, G. F. (2004). What keeps us awake: the neuropharmacology of stimulants and wakefulness promoting medications. Sleep27(6), 1181-1194.
    2. Myhrvold N. (2018). Coffee. Encyclopaedia Britannica.
    3. Sheth, S., Brito, R., Mukherjea, D., Rybak, L. P., & Ramkumar, V. (2014). Adenosine receptors: expression, function and regulation. International journal of molecular sciences, 15(2), 2024-52.
    4. Eteng, M. U., Eyong, E. U., Akpanyung, E. O., Agiang, M. A., & Aremu, C. Y. (1997). Recent advances in caffeine and theobromine toxicities: a review. Plant foods for human nutrition51(3), 231-243.
    5. David D. Gummin, James B. Mowry, Daniel A. Spyker, Daniel E. Brooks, Michael O. Fraser & William Banner. (2017). 2016 Annual Report of the American Association of Poison Control Centers’ National Poison Data System (NPDS): 34th Annual Report, Clinical Toxicology, 55:10, 1072-1254.
    6. Murray A., Taylor J.. (2018). Caffeine Toxicity.
    7. Sepkowitz, K. A. (2013). Energy drinks and caffeine-related adverse effects. Jama309(3), 243-244.
    8. James H. O’Keefe, James J. DiNicolantonio, Carl J. Lavie. (2018). Coffee for Cardioprotection and Longevity. Progess in Cardiovascular Diseases. 69, Issue 1, May-June 2018, 38-42.
    9. Wedick et al.. (2011). Effects of caffeinated and decaffeinated coffee on biological risk factors for type 2 diabetes: a randomized controlled trial. Nutrition Journal. 10:93.
    10. Maria Patrizia Carrieri et al.. (2017). Protective effect of coffee consumption on all-cause mortality of French HIV-HCV co-infected patients. Journal of Hepatology. 67, Issue 6. December 2017. 1157-1167.

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2 Responses

  1. roger says:

    In an MRI machine it shows coffee stops the brain from working.
    Hypertension is a real issue with mental illnesses.

    • Katharina says:

      Hey Roger! I think you are referring to the WorldNews video that shows an MRI scan of the brain. I think you mixed something up, as yes, caffeine does decrease blood flow to the brain, however the brain adapts pretty quickly to that and works normal when drinking coffee regularly. And also while the blood flow is decreased, the brain doesn’t “stop” working, because if that would happen most people would die from drinking coffee.
      As to hypertension: According to an article from Harvard Medical school, it’s still unclear if caffeine consumption actually leads to hypertension. As stated in my article, the studies done on health benefits and risks, as well as mental benefits and risks are very contradictive and don’t really lead to a clear answer. But it’s good to remain skeptical!

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