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All About Coffee – How Coffee Works

Caffeine, the primary active ingredient in coffee, has a well-established reputation for being an energy booster.

However, caffeine is also a drug, which means that it can affect each of us differently, depending on our consumption habits and genetic makeup.

“The paradox of caffeine is that in the short term, it helps with attention and alertness. It aids in some cognitive tasks and boosts energy levels,”

stated by Mark Stein, a professor in the Department of Psychiatry and Behavioral Sciences at the University of Washington, who has conducted studies on the impact of caffeine on individuals with A.D.H.D.

“But the cumulative effect — or the long-term impact — has the opposite effect.”

What is the coffee paradox

Part of the paradoxical effects of caffeine is a result of its impact on what researchers refer to as “sleep pressure,” which determines how sleepy we become as the day progresses. From the moment we wake up, our bodies have a biological clock that drives us to feel sleepy later in the day.

Sleep pressure builds up in the body as cells and tissues use and burn energy in the form of a molecule called adenosine triphosphate, or ATP. As ATP is expended through activities like thinking, exercising, running errands, or engaging in conference calls, adenosine is generated as a byproduct. Adenosine then binds to receptors in the brain, making us feel more tired.

Chemically, caffeine bears resemblance to adenosine on a molecular level, enabling it to occupy those binding sites and prevent adenosine from binding to the brain receptors. Consequently, caffeine works temporarily to suppress sleep pressure and make us feel more awake, while adenosine continues to accumulate in the body.

“When the effects of caffeine wear off, sleep pressure increases significantly, and it must be repaid,” explained Dr. Blackshaw. In fact, sleep is the only way to alleviate and reset elevated sleep pressure.

Adding to the issue, the more caffeine we consume, the higher our body’s tolerance to it becomes. Our liver adjusts by producing proteins that break down caffeine more quickly, and the adenosine receptors in our brain multiply to maintain sensitivity to adenosine levels for regulating our sleep cycle.

Ultimately, continued or increased caffeine consumption adversely affects sleep, leading to increased tiredness, according to Dr. Stein.

“If you’re sleeping less, stressed, and relying on caffeine to improve it, it’s a perfect storm for a short-term solution that worsens things in the long run,” he said. “You may be adding more shots to your espresso, but the negative impact on your sleep will persist and accumulate.”

Caffeine may also cause blood sugar spikes or dehydration, both of which can contribute to increased tiredness, as mentioned by Christina Pierpaoli Parker, a clinical researcher studying sleep at the University of Alabama at Birmingham.

If someone is experiencing an afternoon slump even after drinking a cup of coffee, scientists recommend consuming less of it. Avoid drinking it daily or try abstaining from it for a few days to allow the body to eliminate any caffeine from our system, then gradually reintroduce it into our routine. Ideally, drinking coffee should be enjoyable and beneficial, providing a boost when needed, according to Dr. Blackshaw.

In the meantime, if we feel like caffeine is no longer providing an energy boost, experts suggest taking a nap, engaging in exercise, or spending time outdoors to get some natural light, which can naturally increase energy levels.

“Monitor your sleep and ensure you’re getting adequate rest,” advised Dr. Stein. “Sufficient sleep and physical activity are the primary interventions for attention problems and sleepiness. Caffeine can be a helpful addition, but you don’t want to become dependent on it.”

Why coffee is addictive

As we consume more coffee, our body builds more adenosine receptors, necessitating an increased amount of coffee to keep us awake. The number of adenosine receptors formed, increases with higher coffee consumption, making it necessary to consume more coffee than when we first started drinking it as a young adult.

Caffeine also boosts our adrenaline levels, increasing heart rate and promoting faster blood flow. At the same time, caffeine prevents dopamine from being reabsorbed into our system, causing it to linger in the brain for a longer duration. This prolonged presence of dopamine contributes to the positive effects of caffeine, such as feelings of happiness. This dopamine effect often triggers the brain to crave more caffeine because dopamine plays a significant role in various addictions.

What’s the coffee time-frame?

According to research, caffeine has a half-life of approximately 6 hours.

  • Within the first 10 minutes of consumption, caffeine enters our bloodstream, causing an increase in blood pressure and heart rate.
  • Around 20 minutes later, caffeine binds to the adenosine receptors, alleviating fatigue and boosting dopamine levels, resulting in a sense of alertness and focus.
  • Within 30 minutes, our adrenal glands become more active, producing additional hormones. During this time, our vision may become sharper due to dilated pupils.
  • Within 40 minutes, the body increases the production of serotonin, improving neuron function in the  spinal cord, leading to enhanced coordination and muscle strength.
  • After 4 hours, the metabolism increases, resulting in faster energy consumption and the breakdown of stored fats.
  • Within 6 hours, the caffeine has been processed and eliminated from our system, and we may feel the need to urinate as approximately half of the consumed caffeine is expelled.

When is the best time to drink coffee?

Consuming caffeine when cortisol levels are high can have negative health effects. Cortisol, a stress hormone with a distinct circadian rhythm regulated by the brain’s central pacemaker, plays a role in metabolic functions, fatigue, and overall well-being. Disrupting this rhythm by consuming caffeine during peak cortisol levels can interfere with cortisol production and increase tolerance, impacting our response to stress and leading to a greater dependence on caffeine over time.

The best time to drink coffee avoids the natural peaks of cortisol in our body, which occur three times a day, including in the early morning. The optimal times to consume coffee or caffeine are between 10 a.m. and 12 pm, and again between 2 p.m. and 5 p.m. This allows the brain to maximize the benefits of caffeine without interfering with other essential functions like cortisol release, which naturally occurs multiple times throughout the day.

Enough sleep, yet still feel tired after drinking coffee?

If we add sugar to our coffee, we may experience regular crashes in energy levels. Specialty coffee drinks often include added sugars in the form of whipped cream or syrup. The body processes sugar faster than caffeine, and once the sugar is used up, we may experience a sudden drop in energy. The timing of this crash varies from person to person but can occur within approximately 90 minutes after consuming sugar.

Can coffee really boost athletic performance?

Absolutely. A 2020 study on amateur cyclists found that coffee improved performance by an average of 1.7%. While this may not seem significant, it can make a notable difference for moderately competitive athletes. Previous British research also reported an improvement in reaction times, memory, and visual-spatial reasoning among coffee consumers.

Most of these performance benefits come from caffeine, which is why coffee may not always be the best option. Different coffees offer varying amounts of caffeine, and factors such as brewing method, bean type, and serving size can affect the caffeine content. It’s important to consider these factors if we’re specifically looking to enhance athletic performance through coffee consumption.

In addition to caffeine, coffee contains other compounds that may contribute to its potential performance-boosting effects. For example, coffee is rich in antioxidants, such as chlorogenic acid, which have been linked to improved exercise performance and reduced muscle damage. Coffee also contains minerals like potassium and magnesium, which are important for muscle function and recovery.

However, it’s worth noting that individual responses to caffeine can vary. Some people may be more sensitive to its effects, while others may have a higher tolerance. It’s important to experiment and find what works best for our own body.

When it comes to timing, consuming coffee about 30 minutes to an hour before exercise can be beneficial. This allows enough time for caffeine to be absorbed into the bloodstream and exert its effects. However, it’s important to listen to our body and adjust the timing based on how caffeine affects us personally. Some individuals may experience digestive discomfort or jitteriness if they consume coffee too close to their workout.

It’s also important to consider hydration when using coffee as a performance-enhancing aid. Coffee is a diuretic, which means it can increase urine production and potentially contribute to dehydration if not consumed alongside adequate fluids. To counteract this, it’s recommended to drink additional water when consuming coffee before exercise.

When should we stop drinking it?

This is a topic of debate. Caffeine has a half-life of approximately six hours, which means that if we have our final espresso at 4pm, half of the caffeine is still present in our system at 10pm, when we should be winding down for the night. The idea of a caffeine curfew, such as stopping at 2pm or 3pm, is embraced by many, but that doesn’t mean it’s open season in the morning.

“It should be approached as a nice, balanced thing,”

says Nick Littlehales, a sleep coach who has worked with several high-profile football teams.

“I observe many individuals who have three coffees more or less consecutively in the morning. They end up consuming 1,000-1,500mg before lunchtime and then cease their intake. That’s not a sensible approach: it’s about maintaining a steady level, without significant fluctuations. Keep track of when you experience a slight decrease in energy, and then you can strategically utilize caffeine intake to assist you during crucial times.”

Can Overdoing Caffeine Be Dangerous?

According to the latest Dietary Guidelines for Americans from the Department of Agriculture, up to 400 mg of caffeine per day – the amount in two to four 8-ounce cups of coffee – can be included in our healthy diet as adults. It is stated by the Food and Drug Administration that 600 mg per day is considered excessive.

While tolerances may vary, exceeding our regular caffeine intake could result in feelings of nervousness, anxiety, irritability, jitters, and may contribute to excessive urine production or irregular heartbeat, as mentioned by caffeine researcher Maggie Sweeney, Ph.D., a postdoctoral research fellow at the behavioral pharmacology research unit at Johns Hopkins University School of Medicine. These effects could occur even in individuals accustomed to caffeine consumption. Moreover, for those who experience anxiety or insomnia, it could exacerbate their symptoms.

Our caffeine consumption can easily accumulate if we drink coffee and also consume multiple caffeinated products throughout the day. For example, having a Starbucks coffee in the morning, a caffeinated water in the afternoon, and a few caffeinated mints during the day could result in exceeding 600 mg.

At extremely high doses, caffeine can lead to vomiting, convulsions, heart attack, and even death. An illustrative case is the unfortunate incident in 2014, where two young and healthy men died after overdosing on pure, powdered caffeine purchased online. Just 1 teaspoon of it contains the same amount of caffeine as approximately 28 cups of coffee. Although such cases are rare, they serve as a reminder of the potential risks associated with excessive caffeine consumption.

Is it beneficial for us?

This is where the other biologically active compounds come into play. It’s also where the scientific evidence becomes less clear. Some suggest that excessive consumption may be associated with an increased risk of cancer or heart problems, while others claim that a few cups a day are perfectly fine.

Examining meta-analyses of numerous studies, or even better, an “umbrella review,” can be helpful. One of the largest umbrella reviews conducted in 2017, which analyzed over 200 meta-analyses, concluded:

“Coffee consumption appears to be generally safe within normal levels of intake, with the greatest risk reduction for various health outcomes seen at three to four cups a day, and more likely to provide health benefits than harm.”

Another review from the same year found that coffee was likely to decrease the risk of various forms of cancer, cardiovascular disease, Parkinson’s disease, and type 2 diabetes.


  • Coffee acts by preventing the substance signaling tiredness being delivered to their receptors.
  • Once the receptors are overwhelmed sleep comes crushing down.
  • The only way to reset our sleep counter is sleeping.
  • Coffee is an addictive substance and thus requires its amount constantly increased for the same results.
  • Coffee can boost athletic performance but for best results it’s recommended to take it in controlled form.

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