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Common FAQs for caffeine

Caffeine is an ever-present part of our daily routines in the 21st century.

As gaming blends and pre-workout blends gain traction and popularity, our innovation manager, Amy Lynch ANutr, thought it would be prudent to deep-dive into this category, the uses, benefits and side-effects.

What are stimulants?

Stimulants are compounds that interact with our central nervous system (CNS) to increase the activity of the brain. There are many drugs that fall into the category of "stimulant", among these is caffeine. 

What is caffeine?

The chemical name for caffeine is 1,3,7 trimethylanthine. It is a "mild" stimulant and it can be found in beverages such as tea, coffee and fizzy drinks. Its primary source is coffee, but it can also be found in guarana berries and cacao beans too. Caffeine can be extracted from green coffee beans, tea leaves and cola nuts. Additionally, it can be chemically synthesised (1).

How is caffeine metabolised?

Caffeine is absorbed in the small intestine within 45 minutes of oral administration, and it can readily pass the blood-brain barrier (2). Caffeine is primarily metabolized in the liver (3) and a small percentage is excreted, unmetabolized, into the urine, bile, saliva and breast milk (1).

What is the science behind caffeine?

Caffeine causes most of its biological effects by blocking adenosine receptors (4). Adenosine is a known somnogen and induces sleep via binding to its receptors (6). Adenosine accumulates in the brain throughout the waking hours and create "sleep pressure." Adenosine dissipates during sleep (6). Additionally, caffeine can also affect ryanodine receptors (RyRs) (7). This causes Ca+ ions to be released into muscle cells, leading to improved muscle speed and strength (8). Furthermore, caffeine has been shown to reduce pain perception during high intensity exercise (9).

What is beneficial about this for a pre-workout?

All of this is highly useful for products that aim to keep its consumer alert and able to keep pushing during bouts of exercise or work that requires peak cognitive functioning.

What are the drawbacks of caffeine?

Some draw backs of caffeine include nervousness, anxiety, muscle tremors, irritability and in some cases arrhythmia and high blood pressure (10). Many of these undesirable effects are dose-dependent (11). The threshold of toxicity is 400mg/ day in healthy adults (19 years or older) (12).

What are some other options?

  • Caffeine is a unique compound with varying actions on the body. However, there are other ingredients on the market if you are looking to avoid the negative side-effects.
  • Creatine - Creatine has been shown to increase ATP synthesis by increasing the quantity of Pi available for the reaction - ADP + Pi = ATP (13)
  • CellFlo6® - This is a specialised green tea extract that has been shown to help improve blood flow and increase nitric oxide production beyond that of citrulline and arginine (14).
  • Beta-Alanine - This has been shown to improve high - intensity exercise performance (15). It achieves this by binding to hydrogen ions in the muscles, decreasing intracellular acidity (16).


      (1) IARC, 1991. Coffee, tea, mate, methylxanthines and methylglyoxal: Monographs on the evaluation of the carcinogenic risk of chemicals to humans.

(2) Tavares, C. and Sakata, R.K., 2012. Caffeine in the treatment of pain. Revista brasileira de anestesiologia62, pp.394-401.

(3) Fredholm, B.B. and Arnaud, M.J., 2011. Pharmacokinetics and metabolism of natural methylxanthines in animal and man. Methylxanthines, pp.33-91.

(4)Ribeiro, J.A. and Sebastiao, A.M., 2010. Caffeine and adenosine. Journal of Alzheimer's Disease20(s1), pp.S3-S15.

(5)Huang, Z.L., Urade, Y., Hayaishi, O., (2011). 'The Role of Adenosine in the Regulation of Sleep', Current Topics in Medicinal Chemistry, 11(8), Available at: (Accessed: [30/05/2024]).

(6) Adenosine A2A receptors and sleep. (2023). International Review of Neurobiology, [online] Available at: [Accessed 30/05/2024].

(7) Del Coso, J., Muñoz, G. and Muñoz-Guerra, J., 2011. Prevalence of caffeine use in elite athletes following its removal from the World Anti-Doping Agency list of banned substances. Applied physiology, nutrition, and metabolism, 36(4), pp.555-561.

(8) Warren, G.L., Park, N.D., Maresca, R.D., McKibans, K.I. and Millard-Stafford, M.L., 2010. Effect of caffeine ingestion on muscular strength and endurance: a meta-analysis. Medicine & Science in Sports & Exercise42(7), pp.1375-1387.

(9) Astorino, T.A., Terzi, M.N., Roberson, D.W. and Burnett, T.R., 2011. Effect of caffeine intake on pain perception during high-intensity exercise. International journal of sport nutrition and exercise metabolism, 21(1), pp.27-32.

(10) Rodak, K.; Kokot, I.; Kratz, E.M. Caffeine as a Factor Influencing the Functioning of the Human Body—Friend or Foe? Nutrients 202113, 3088.

(11) Musgrave, I.F., Farrington, R.L., Hoban, C. and Byard, R.W., 2016. Caffeine toxicity in forensic practice: possible effects and under-appreciated sources. Forensic science, medicine, and pathology12, pp.299-303.

(12) Nawrot, P., Jordan, S., Eastwood, J., Rotstein, J., Hugenholtz, A. and Feeley, M., 2003. Effects of caffeine on human health. Food Additives & Contaminants20(1), pp.1-30.

(13) Iacone, R., 2021. Creatine in Health and Disease. Nutrients, [e-journal] 13(2), 447. Available at: [30/05/2024].

(14) Fox, C.D., Garner, C.T., Mumford, P.W., Beck, D.T. and Roberts, M.D., 2020. Higher doses of a green tea-based supplement increase post-exercise blood flow following an acute resistance exercise bout in recreationally resistance-trained college-aged men. Journal of the International Society of Sports Nutrition, 17(1), p.27. Available at: [30/05/2024)

(15) Saunders B, Elliott-Sale K, Artioli GG, Swinton PA, Dolan E, Roschel H, Sale C, Gualano B. β-alanine supplementation to improve exercise capacity and performance: a systematic review and meta-analysis. Br J Sports Med. 2017 Apr;51(8):658-669. doi: 10.1136/bjsports-2016-096396. Epub 2016 Oct 18. PMID: 27797728.

(16) (n.d.). Beta-Alanine. Available at: [30/05/2024].

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