How Does Caffeine Work?

Whether it’s a morning coffee, energy drink, or supplement, billions of people rely on caffeine to get them awake and alert for the day ahead, making it the most widely consumed psychostimulants in the world. It is estimated that caffeine is being consumed by more than 80% of the world’s population and up to 89% of the United States population (typically in teas and coffee) [1]. But what is this popular substance and how does it work? Is it safe to take? How much is a standard dose? Let’s dive into what this stimulating substance is all about.

What is Caffeine?

Caffeine is a natural stimulant found naturally in cacao beans and more than 60 other plant species [1]. It is the most popular natural stimulant typically found naturally in coffees and teas, but more recently found added into supplements such as pre workouts and nootropic supplements. These supplements typically either use the natural form of caffeine found in plants, or a synthetic, more concentration version. This synthetic version is typically found in energy drinks and sodas, and hits the blood stream even faster than the natural source resulting in quicker effects but an even quicker crash. Both forms of caffeine have been reported in a variety of different research studies to enhance physical and mental performance shortly after being ingested [1-5]. 

How Does It Work?

Once consumed, caffeine is quickly absorbed from the gut into the blood stream where it is then broken down into compounds in the liver that are able to effect the brain in a variety of different ways. The primary way that caffeine works is by functioning as an adenosine receptor antagonist in the brain [1, 2]. Adenosine is a molecule that when bound to its receptors, slows down neural activity in the brain causing us to feel sleepy. Because of caffeine’s similar structure to adenosine, caffeine is able to bind to these adenosine receptors, blocking this pathway and the sleepy feelings associated with adenosine [2, 4]. Caffeine also stimulates the release of adrenaline, our fight or flight hormone, causing an increase in feelings such as arousal, alertness, energy, and concentration [1, 4].

Is Caffeine Safe?

A variety of studies have concluded that caffeine consumption is generally safe, although it is habit forming and can result in mild withdraw symptoms when consumption is stopped after long periods of use [6]. Although moderate amounts of caffeine supplementation have been shown to have positive benefits, too much caffeine has been linked to negative side effects such as anxiety, restlessness, and headaches [6]. These symptoms are typically seen when doses go above the maximum recommended dose of 400 mg, roughly 4 cups of coffee. 

How much should I be taking?

A variety of studies have concluded that roughly 2-4g caffeine/kg bodyweight (roughly 100-400 mg) has been shown to elicit the positive effects of caffeine supplementation [3, 5]. There’s a wide range of sensitivities when it comes to the effects of caffeine, so its recommended to start with a lower dose at first and in moderation to avoid symptoms of withdraw. 

The Bottom Line -

Caffeine isn’t as unhealthy as it was once believed to be, whether taken has a daily energizer or as a performance supplement. In fact, studies are continually reporting increased benefits linked to moderate caffeine intake within the recommended daily amounts. Therefore, it’s safe to consider your daily coffee, tea, or supplement as an enjoyable way to promote good health and a productive day!

WRITTEN BY DAVID LEVINSON, BS NUTRITION, NASM CPT AND CES 

References:

1. Willson, C., The clinical toxicology of caffeine: A review and case study. Toxicology Reports, 2018. 5: p. 1140-1152.

2. Urry, E. and H.-P. Landolt, Adenosine, Caffeine, and Performance: From Cognitive Neuroscience of Sleep to Sleep Pharmacogenetics, in Sleep, Neuronal Plasticity and Brain Function. 2014, Springer Berlin Heidelberg. p. 331-366.

3. Guest, N.S., et al., International society of sports nutrition position stand: caffeine and exercise performance. Journal of the International Society of Sports Nutrition, 2021. 18(1).

4. Aguiar, A.S., et al., Neuronal adenosine A2A receptors signal ergogenic effects of caffeine. Scientific Reports, 2020. 10(1).

5. Lorenzo Calvo, J., et al., Caffeine and Cognitive Functions in Sports: A Systematic Review and Meta-Analysis. Nutrients, 2021. 13(3): p. 868.

6. Soós, R., et al., Effects of Caffeine and Caffeinated Beverages in Children, Adolescents and Young Adults: Short Review. International Journal of Environmental Research and Public Health, 2021. 18(23): p. 12389.