Few drugs have influenced the world as greatly as caffeine. Modern businesses are fueled by caffeine-filled robots and few students have escaped the all-night caffeine binge associated with long-procrastinated school work. I grew up completely anti-caffeine if I could help it. Other than a bit of dark chocolate and tea every once in a while, caffeine was excluded from my diet. Not only did I hate the taste of coffee, but I thought caffeine was unhealthy. To set the record straight, I did a “bit” of research.

Caffeine comes in many forms and is not only useful, but also healthy in the right doses.

Caffeine and Your Body

The main purpose of caffeine is to block adenosine, which is a sleep inducing factor. This neurotransmitter is found in the body throughout the day and peaks before bed. Nighttime adenosine levels are low and caffeine acts as an antagonist.

Maintaining alertness and staying awake are perhaps the best known uses for caffeine in popular culture, but that really only scratches the surface.

Not All Caffeine is Created Equal

In your day-to-day life, the differences in caffeine may seem negligible, but they exist. Coffee is not the same as dark chocolate and both are different from tea.

Caffeine from coffee beans is the strongest within the methylxanthines family. Chocolate contains theobromine, which is a kind of methylxanthine. Teas are typically filled with theophylline.

These scientific terms are not important. Caffeine from coffee does not last as long within your body, but has a much stronger effect than chocolate or tea. Knowing this can help you determine what caffeine types to avoid if you want to enjoy a good night’s rest… if that myth is true.

Caffeine Impacts on Sleep

As mentioned previously, the main sleep neurotransmitter is adenosine. As this cumulates throughout the day, you will get more tired. Caffeine is an adenosine antagonist, which is why so many people drink it early in the morning so that they can “wake up”. Logically, it makes sense to avoid highly caffeinated beverages before going to sleep.

Recent studies indicate a completely different pattern. Patients given 4 mg of caffeine per kg of body weight 20 minutes before bed saw only a doubling on their sleep onset latencies (meaning it took twice as long to fall asleep). That is in the extreme situation of drinking caffeine at a medium dose 20 minutes before trying to sleep. However, dose does matter. Taking 8 mg / kg of caffeine decreased sleep efficiency by 17% and tripled the number of awakenings during the night.

Caffeine impacts are different for everyone (I’ll stress this consistently). Just because 4 mg/kg of caffeine 20 minutes before bed showed negligible impacts on sleep does NOT mean it will be the same way for you. Caffeine has an average half-life of around 5 hours in adults so a safe bet is to avoid caffeine 3-4 hours before bed if you are worried.

I’m just as guilty as anyone, but caffeine’s impact on our brain and body is as much a placebo as anything physiological. Studies have shown that placebo caffeine pills keep people awake as much as real administered caffeine. It might just be in your head!

Hormonal and Neurotransmitter Impacts of Caffeine

As hormones and neurotransmitters are the building blocks for all responses and actions in your body, it is only natural to view caffeine from this perspective.

Adrenaline – taking caffeine can increase adrenaline levels for short periods. Excessive caffeine can burn out your adrenal glands, but studies have shown temporary boosts of 37% in many caffeine users. This effect is one of the reasons why strength athletes and body builders choose to take pre-workout supplements or drink coffee before they visit the gym. Tracking my own data, I see a direct correlation between caffeine and positive performance in the gym.

Cortisol – although a balance of cortisol in your body is a good thing, most people in modern society have far too much. Cortisol is a stress hormone which can cause serious metabolic and cognition impacts on your brain and body. Despite popular perception, cortisol is unaffected (or negligibly affected) by caffeine consumption.

Melatonin – the primary use for melatonin is sleep, but the hormone is well regulated all day. Both melatonin and serotonin are balanced, but caffeine seems to suppress or delay melatonin levels. This is another reason caffeine might make it more difficult for you to sleep. That being said, placebo studies have shown that people associate caffeine with restlessness, which often manifests in itself!

Norepinephrine – the lesser known hormone, norepinephrine, is increased by caffeine as well. While this does not have noticeable impacts on your body, it can lead to changes in other important hormones over time.

Insulin – insulin sensitivity is a key problem plaguing modern humans. The increased epinephrine seems to reduce insulin sensitivity in humans over time. However, the biggest problem to insulin sensitivity in modern culture is the consumption of refined and processed carbohydrates and sugars. Any small alterations by coffee will pale in comparison to most diets. Those practicing a more Paleo-style / whole foods diet will see little trouble with insulin sensitivity.

Brain Benefits of Caffeine

Everyone who consumes caffeine or lives in a “coffee culture” is well aware of the positive mental impacts. How specifically caffeine affects your brain is less well known. For example, caffeine can decrease ability to perform complex tasks while increasing efficiency of easy / monotonous tasks.

Mood variability – a friend recently mentioned how much happier he felt after drinking coffee, which is a very normal response. Low to medium doses of caffeine can increase positive mood states. High doses often lead to anxiety and further stress. This is definitely a factor when evaluating caffeine addicts.

Alertness – caffeine directly influences your brain’s alertness and puts you in an aroused state. The increased adrenaline is a by-product associated with alertness. The alertness manifests in reduced reaction times in people of all ages (according to the study, at normal room temperature, but not unusually low temperatures).

Focus – caffeine enhances the ability to focus on selective attention tasks. Studies have shown improved response times and accuracy with caffeine consumption. I have noticed when I drink coffee before strength training in the gym that my focus is incredibly intense. As I walk to the gym, I focus on trees, cars, and other objects. Until researched, I had no idea why this occurred.

Memory – memory is the least studied of caffeine’s impacts and has mixed evidence. Many studies indicate enhanced recall, working, and semantic memory. Others have shown long and short-term memory benefits, but none of the results have been conclusive. Caffeine does have a positive effect of memory preservation in elderly and has been linked to prevent Parkinson’s disease.

Caffeine Dosages

Despite all of the evidence that suggests caffeine is actually healthy and useful, dosage plays a significant role. Research indicates that there is an optimal range of caffeine consumption and increasing consumption does not provide enhanced results.

One dosage study showed that a 200 mg dose of caffeine (about one cup of coffee) improved the accuracy and speed of problem solving. Isolating only the dosage variables, 400 mg actually impaired speed and accuracy of problem solving. Another study showed cognitive performance declined rapidly after 600 mg of caffeine. Sensory perception benefits also seem to result from 90 – 180 mg doses of caffeine.

Caffeine intoxication studies imply that chronic / acute overconsumption of 500-600 mg can lead to significant long term health problems as well. While research is limited, excessive caffeine is implicated in disorders like depression, ADHD, and others. Long story short, the old adage about “too much of a good thing is a bad thing” holds true for caffeine as it does with most things.

That isn’t to say that you are not different than the average / study cohort. My personal trainer, Keith Norris, consumes tons of caffeine daily without any problems. It seems that 200-300 mg of caffeine a day is a good guide to follow based on the wealth of scientific data, but it is up to you to determine what your body can and cannot handle.

I consume 250 – 300 mg of caffeine every 4 – 6 days in the form of coffee. Consumption corresponds directly with high intensity weight lifting / strength training sessions and rarely otherwise. My 85% dark chocolate has considerable caffeine as well, but closer to 50 – 85mg every 2-3 days.

Your body’s reaction to caffeine will depend on dosage and consumption frequency. I like to drink coffee about once every 5 days because I am quite sensitive to small doses. As with sleep, caffeine should be used as a tool rather than abused.

External resources:

Daly, John and Fredholm, Bertil. “Mechanisms of Action of Caffeine on the Nervous System”

Snel, Tieges, Lorist. “Effects of Caffeine on Sleep and Wakefulness: An Update”

Smith, Osborne, Mann, Jones, White. “Arousal and Behavior: Biopsychological Effects of Caffeine”

Nehlig, Astrid (ed). “Coffee, Tea, Chocolate, and the Brain.” 2004.

Blanchard J, Sawers SJ. “Comparative pharmacokinetics of caffeine in young and elderly men.” J Pharmacokinet Biopharm. 1983 April; 9 – 26