Coffee’s fantastic aromas and simulative effects have engrained the beverage in many cultures. Coffee or caffeine really, is the most used over-the-counter natural stimulant drug.

Caffeine is a substance found in the beans, leaves and fruits of more than 60 different types of plants in over 50 countries worldwide. Coffee, tea, cocoa, chocolate and energy drinks all contain caffeine.

There is a lot of controversy around coffee consumption and its effects on health. Based on many articles and research pieces, we have summarised the pros and cons below.


Let’s start with looking at the impact of caffeine on different people.  We always wondered how some people can drink eight cups of coffee a day and feel great while others are bouncing around like a Skippy ball all day after one cup of coffee! Impact of caffeine varies from person to person.

Interestingly, the strength and duration of caffeine’s effect depends on a number of factors including tolerance, genetics and other factors. Stephen Brain, in his book “The Science and Lore of Alcohol and Caffeine”, found that “The average half-life of caffeine—that is, how long it takes for half of an ingested dose to wear off—is about five to six hours in a human body. Women taking oral birth control require about twice as long to process caffeine. Women between the ovulation and beginning of menstruation see a similar, if less severe, extended half-life. For regular smokers, caffeine takes half as long to process—which, in some ways, explains why smokers often drink more coffee and feel more agitated and anxious, because they’re unaware of how their bodies work without cigarettes. As one starts to regularly take in caffeine, the body and mind build up a tolerance to it, so getting the same kind of boost as one’s first-ever sip takes more caffeine—this, researchers can agree on. Exactly how that tolerance develops is not so clear.”


Now we know that caffeine impacts people differently, let’s look at how it impacts the body.

Caffeine has an impact on the sympathetic nervous system by mobilising the body for the fight or flight response.  When in fight or flight mode, adrenaline is secreted, primarily impacting the cardiovascular system and sending this into overdrive increasing heart rate and metabolism, causing vasoconstriction of vessels and inducing temporary improvements in both mental and physical functions. No wonder that most of us enjoy the simulative side effects!


Given caffeine’s effects, you won’t be surprised to hear that athletes enjoy consuming caffeine.  Most studies on caffeine and athletic performance found that caffeine enhances endurance performance. The performance enhancement comes from improved alertness and reaction time, as well as reduction in perceived effort, so you work harder without feeling the extra effort. In fact, the International Olympic Committee treated caffeine as a banned substance until 2000 because of its simulative side effects.


As mentioned previously, effects of caffeine vary by person and vary with quantity consumed.

Positive effects:

  • Lower risk of cardiovascular disease and diabetes experienced with high and long-term consumption
  • Reduced risk of disease such as Alzheimer disease, Parkinson disease and type 2 diabetes
  • Increased levels of neurotransmitters leading to feelings of euphoria
  • Increased alertness and decreased feelings of fatigue
  • Increased metabolic rate leading to potential weight loss
  • Prevention and delay of some types of cell damage from antioxidants in coffee

Negative effects:

  • Increased cortisol secretion leading to increased stress levels potentially damaging the immune system
  • Increased blood pressure increasing the risk of heart disease
  • Reduced quality of sleep potentially contributing to insomnia and sleep latency
  • Anxiety experienced with high consumption
  • Addictive qualities as withdrawal can produce headache, fatigue and decreased alertness

In summary, caffeine impacts everyone differently so should be evaluated person by person. In general; consuming one or two cups of coffee a day has beneficial physiological effects, in particular when exercising,  and can also have positive mental effects due to pleasure derived when drinking coffee. Be aware of excessive amounts of coffee though, as this can cause over activation of the nervous system, increasing stress and fatigue.