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Caffeine Ultimate Guide – Benefits, Dose, & Safety

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Consuming caffeine through coffee, tea, energy drinks or in pill form is a regular habit for over 80% of the US population.

Apart from being a stimulant, caffeine offers many surprising benefits ranging from improved athletic performance (14) to increased fat oxidation or “burning” (1, 9, 13).

With this in mind, it’s no surprise that it’s one of the most widely consumed drugs in the world (7, 12). If you follow my content or utilize one of my advanced workout plans then you will also notice I continually promote caffeine due to its unique benefits.

In this article, I will breakdown how caffeine can benefit you, how to consume or dose caffeine and any potential side effects of Caffeine may have.

Caffeine’s Function, Structure and Metabolism

Caffeine is an alkaloid that is found naturally in many plants such as cocoa and coffee beans.

Caffeine can be consumed in a wide range of products and forms, which likely is one of the reasons for its popularity. Caffeine’s absorption begins in the mouth due to the fact that it can be absorbed through the lining of the mouth, called the buccal mucosa.

Absorbing caffeine through this route is the fasted way for caffeine to be absorbed into the bloodstream.

Due to this absorption, the drinking of coffee improves wakefulness (2) almost immediately. This oral absorption ability is also why caffeinated gum can be an effective way to consume caffeine.

When absorbed through the stomach, caffeine is almost entirely absorbed via the intestinal wall within 45-60 minutes of ingestion. Some studies show caffeine takes around 60-90 minutes after consumption.

This is why I often recommend consuming a pre-workout 30-60 minutes before, not as you walk in the gym (because levels will peak as you leave the gym!) (4).

caffeine benefits

Source: [Júdice, P. B. et. al (2013)]

Caffeine Effects on Energy 

After absorption, caffeine begins to work its magic by acting as an A1 adenosine receptor antagonist.

In the brain, as the day goes on, and the body metabolizes energy (ATP), there is a build up of a molecule called adenosine.

As this build up of adenosine increases, it begins to attach to its adenosine receptor, which in turn, causes feelings of drowsiness and fatigue..

When caffeine is consumed and metabolized, it acts on this receptor and competes with adenosine. If caffeine has managed to block the receptor to adenosine, adenosine is unable to act and cause drowsiness.

In short, it’s basically blocking the build-up of a molecular (adenosine) that tells the brain we are tired and fatigued.

Along with this, caffeine is also a potent nervous system stimulator, igniting both our peripheral (muscle) and central (brain) nervous system, basically increasing its firing rate and increasing force production, brain function or processing ability.

Benefits of Caffeine

Considering its widespread usage around the globe, it’s not surprising that caffeine has an abundance of benefits.

Sprinting capacity: Caffeine seems to promote an anti-fatiguing effect when it comes to being able to sprint or perform exercise for short, high intensity bouts, even in experienced athletes (14).

Decreased rate of perceived exertion: Caffeine ingestion has been revealed to decrease perception of exertion, potentially leading to improved performance as you can workout at the same intensity with less effort (3).

Increased metabolic rate: Studies have revealed that consumption of caffeine may lead to a direct increase in metabolic rate. However, this seems to be only for people who typically consume smaller or less frequent amounts of caffeine (1).

Increased fat oxidation: Caffeine consumption has been revealed to increase the rate at which fat is oxidized or “burned.” This seems to be secondary to caffeine’s ability to increase adrenaline (1, 9, 13). 

Subjective Well-Being: Participants in studies with caffeine have reported increases in measures of subjective well-being, such as vigor. This is likely also related to reductions in fatigue and again, likely beneficial for infrequent caffeine users (6).

How to Consume Caffeine and How to Dose Caffeine 

As mentioned prior, caffeine can be absorbed through the lining of the mouth and through the intestine with nearly perfect efficiency.

Nonetheless, there are multiple different routes by which you can consume caffeine, with wide ranges of caffeine content.

The following are typical vehicles for caffeine consumption and their relative amounts, in milligrams (5).

• Caffeine pills (available on amazon, CVS etc): ~200mg / serving

• Coffee: ~100-150+ mg / 8 oz.

• Caffeinated tea: ~50-60+ mg / 8 Oz.

• Soda: ~30-40+ mg / 12 oz.

• Dark chocolate (90%): ~ 150+ mg / 100g

For myself and many clients, 200-300mg taken 30-60 minutes before a workout seems best. For fat loss or energy, I also personally like 200mg of caffeine in the AM and then 200mg around 2pm. This allows 6-8 hours for it to be metabolized and out of the body by about 10pm (so it doesn’t impact sleep quality).

Some studies have shown that pure caffeine in supplement or tablet form can enhance its benefits, likely because absorption is improved when it’s not consumed with other nutrients or food.

If you’re looking to improve performance or simply don’t care for caffeinated beverages, I tend to recommend it in supplement form. However, if you love a coffee everyday, then this is also a great option, especially as coffee has other health promoting benefits.

Potential Negative Side Effects of Caffeine

Despite its many potential benefits, regular caffeine use does have some potential negative side effects that you’ll want to be aware of.

The first of which is addiction, tolerance and withdrawal, although this is in very extreme cases, those with past stimulant or drug issues should use with caution (10, 15).

Remember, caffeine is a drug, although a mild one. With continued use, regular high dose caffeine consumption can lead to tolerance, meaning that continued use and benefit requires higher and higher doses.

Unfortunately, caffeine eventually has a threshold of diminishing returns. This means that continuously increasing the dosage will eventually not provide further benefit (after around 600-800mg a day), but will negatively affect other aspects, such as your sleep quality (8).

For this reason, I recommend you cycle off when it’s not needed. I always like to do a 2-4 week off-period after a few months of continued use.

Remember, when you stop using caffeine you may also experience withdrawal symptoms such as headaches, tiredness and irritability. This is dependent on the individual; some people are fine (like myself, luckily), whereas some people become like a zombie (11).

Given the potential negative side effects of prolonged high-dose caffeine usage, it is strongly recommended that you stick with moderate caffeine usage such as 200 – 500mg per day.

As it’s a stimulant, it can cause issues for individuals with heart or blood pressure issues. As I always suggest, simply consult a doctor before using caffeine or any other supplements, especially stimulant-based supplements.

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Caffeine Summary

Caffeine is easily one of the most popular substances in the world and likely one of the best sports supplements available.

Caffeine does seem to have many benefits both cognitively and physically, but can also cause issues if you are sensitive to stimulants, have blood pressure/heart issues or have sleeping problems.

Around 150-300mg is the proven dose for most people. It’s best to take it around 45 minutes to an hour before training. Coffee is a good source; however, caffeine pills are also very simple, cost effective and possibly slightly stronger and more beneficial for serious athletes.

While caffeine has many amazing benefits, always check with your doctor or medical professional before consumption.

If you love supplements, you can learn about my 3 Best Fat Burning Supplements (Proven By Science) or 6 Popular Supplements That Don’t Actually Work!


1. Astrup, A., Toubro, S., Cannon, S., Hein, P., Breum, L., & Madsen, J. (1990). Caffeine: a double-blind, placebo-controlled study of its thermogenic, metabolic, and cardiovascular effects in healthy volunteers. The American journal of clinical nutrition, 51(5), 759-767.

2. Barry, R. J., Clarke, A. R., & Johnstone, S. J. (2011). Caffeine and opening the eyes have additive effects on resting arousal measures. Clinical Neurophysiology, 122(10), 2010-2015.

3. Bellar, D., Kamimori, G. H., & Glickman, E. L. (2011). The effects of low-dose caffeine on perceived pain during a grip to exhaustion task. The Journal of Strength & Conditioning Research, 25(5), 1225-1228.

4. Blanchard, J., & Sawers, S. J. (1983). Comparative pharmacokinetics of caffeine in young and elderly men. Journal of Pharmacokinetics and Pharmacodynamics, 11(2), 109-126.

5. Caffeine, I. F. I. C. Health: Clarifying the controversies. IFIC Review, 7(98), 1-8.

6. Childs, E., & De Wit, H. (2006). Subjective, behavioral, and physiological effects of acute caffeine in light, nondependent caffeine users. Psychopharmacology, 185(4), 514.

7. Heckman, M. A., Weil, J., Mejia, D., & Gonzalez, E. (2010). Caffeine (1, 3, 7‐trimethylxanthine) in foods: a comprehensive review on consumption, functionality, safety, and regulatory matters. Journal of food science, 75(3).

8. Hindmarch, I., Rigney, U., Stanley, N., Quinlan, P., Rycroft, J., & Lane, J. (2000). A naturalistic investigation of the effects of day-long consumption of tea, coffee and water on alertness, sleep onset and sleep quality. Psychopharmacology, 149(3), 203-216.

9. Júdice, P. B., Magalhães, J. P., Santos, D. A., Matias, C. N., Carita, A. I., Armada-Da-Silva, P. A., … & Silva, A. M. (2013). A moderate dose of caffeine ingestion does not change energy expenditure but decreases sleep time in physically active males: a double-blind randomized controlled trial. Applied Physiology, Nutrition, and Metabolism, 38(999), 49-56.

10. Keijzers, G. B., De Galan, B. E., Tack, C. J., & Smits, P. (2002). Caffeine can decrease insulin sensitivity in humans. Diabetes care, 25(2), 364-369.

11. Kennedy, D. O., & Haskell, C. F. (2011). Cerebral blood flow and behavioural effects of caffeine in habitual and non-habitual consumers of caffeine: a near infrared spectroscopy study. Biological psychology, 86(3), 298-306.

12. Kennedy, M. D., Galloway, A. V., Dickau, L. J., & Hudson, M. K. (2008). The cumulative effect of coffee and a mental stress task on heart rate, blood pressure, and mental alertness is similar in caffeine-naïve and caffeine-habituated females. Nutrition research, 28(9), 609-614.

13. Knight, C. A., Knight, I., & Mitchell, D. C. (2006). Beverage caffeine intakes in young children in Canada and the US. Canadian Journal of Dietetic Practice and Research, 67(2), 96-99.

14. Norager, C. B., Jensen, M. B., Weimann, A., & Madsen, M. R. (2006). Metabolic effects of caffeine ingestion and physical work in 75‐year old citizens. A randomized, double‐blind, placebo‐controlled, cross‐over study. Clinical endocrinology, 65(2), 223-228.

15. Schneiker, K. T., Bishop, D., Dawson, B., & Hackett, L. P. (2006). Effects of caffeine on prolonged intermittent-sprint ability in team-sport athletes. Medicine and science in sports and exercise, 38(3), 578.

16. Zwyghuizen-Doorenbos, A., Roehrs, T. A., Lipschutz, L., Timms, V., & Roth, T. (1990). Effects of caffeine on alertness. Psychopharmacology, 100(1), 36-39.

About the author


Rudy Mawer, MSc, CISSN

Rudy has a 1st class BSc in Exercise, Nutrition & Health and a Masters in Exercise & Nutrition Science from the University of Tampa. Rudy currently works as a Human Performance Researcher, Sports Nutritionist and Physique Coach. Over 7 years he has helped over 500 people around the world achieve long last physique transformations.

He now works closely with a variety of professional athletes and teams, including the NBA, USA Athletics, World Triathlon Gold Medalists, Hollywood Celebrities and IFBB Pro Bodybuilders. If you would like to get in contact or work with Rudy please contact him on social media.

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