Around 1.6 billion cups of coffee are consumed each day and the caffeine in coffee is the most consumed psychoactive drug in the world (Temple et al., 2017). Coffee is most known for providing energy from its caffeine content and used to take trendy instagram pictures, but it's also well known for contributing to increased urination frequency or diuresis. Adults are often recommended to decrease caffeinated beverages in order to reach optimum hydration levels. This thought is rooted in the fact that caffeine causes a diuretic effect, possibly leading to dehydration when consumed in excessive amounts. Caffeine works by binding to adenosine receptors, a type of g-protein coupled receptor located all throughout the body, and blocks adenosine from binding, therefore resulting in various effects based on the type of adenosine receptor (Temple et al., 2017). For example, Adenosine receptor A1 is located throughout the central nervous system and results in a decrease in adenylate cyclase, cyclic AMP production, and a decrease in protein kinase A activity, while adenosine receptor A2 increases cyclic AMP production and protein kinase A activity (Sheth et al., 2014). Caffeine induces its diuretic effect by binding to adenosine receptor A1 in the kidneys causing an increases glomerular filtration rate and by inhibiting Na+ reabsorption in the proximal tubules of the nephron (Marx et al., 2016). Inhibiting Na+ reabsorpiton causes an increase in Na+ excretion, therefore contributing to caffeine's diuretic effect.
Although the caffeine in coffee increases urination frequency, it does not significantly increase dehydration amongst healthy adults who consume up to the maximum recommendation of 400 mg of caffeine daily (Temple et al., 2017). In a study conducted in men who drank 3-6 cups of coffee every day, moderate caffeine intake (up to 400 mg) did not cause a significant decrease in total body water when compared to a control group that only consumed water (Killer et al., 2014). In fact, consuming 3 mg of caffeine per 1 kg of our body does not contribute to any disturbance in fluid balance in healthy adults who regularly consume caffeine (Seal et al., 2017). In conclusion, coffee can be included in daily hydration requirements and isn’t shown to have any detrimental effects to fluid volume in the body. Thus, coffee consumed in moderation does not cause an increase in dehydration levels, even with an increase in sodium excretion.
Temple, J. L., Bernard, C., Lipshultz, S. E., Czachor, J. D., Westphal, J. A., & Mestre, M. A. (2017). The Safety of Ingested Caffeine: A Comprehensive Review. Frontiers in psychiatry, 8, 80. https://doi.org/10.3389/fpsyt.2017.00080
Sheth, S., Brito, R., Mukherjea, D., Rybak, L. P., & Ramkumar, V. (2014). Adenosine receptors: expression, function and regulation. International journal of molecular sciences, 15(2), 2024–2052. https://doi.org/10.3390/ijms15022024
Marx, B., Scuvée, É., Scuvée-Moreau, J., Seutin, V., & Jouret, F. (2016). Mécanismes de l'effet diurétique de la caféine [Mechanisms of caffeine-induced diuresis]. Medecine sciences : M/S, 32(5), 485–490. https://doi.org/10.1051/medsci/20163205015
Killer, S. C., Blannin, A. K., & Jeukendrup, A. E. (2014). No evidence of dehydration with moderate daily coffee intake: a counterbalanced cross-over study in a free-living population. PloS one, 9(1), e84154. https://doi.org/10.1371/journal.pone.0084154
Seal, A. D., Bardis, C. N., Gavrieli, A., Grigorakis, P., Adams, J. D., Arnaoutis, G., Yannakoulia, M., & Kavouras, S. A. (2017). Coffee with High but Not Low Caffeine Content Augments Fluid and Electrolyte Excretion at Rest. Frontiers in nutrition, 4, 40. https://doi.org/10.3389/fnut.2017.00040
Collin,
ReplyDeleteIt is really interesting to see the exact mechanism of action of the diuretic effects of caffein. Another reason why intake of caffeine does not cause dehydration is possible due to the fact that with the vast majority of caffeine intake, you are consuming water along with it. One study that I found mentions that only acute consumption of large amounts of caffeine cause diuretic affects while normal doses (such as in tea and coffee) have no effects. Furthermore, the diuretic effects are only seen when people take those large doses after not having caffeine for weeks. If people habitually consume caffeine, then this diuretic effect is significantly diminished. So, this myth is very obviously false, especially for those people who have caffeine on a daily basis.
Maughan, R. J., & Griffin, J. (2003). Caffeine ingestion and fluid balance: a review. Journal of human nutrition and dietetics : the official journal of the British Dietetic Association, 16(6), 411–420. https://doi-org.dml.regis.edu/10.1046/j.1365-277x.2003.00477.x
This is an interesting topic since so many people consume coffee. I got some friends that can consume about 3 to 5 cups of coffee each day and a day without coffee with them sometimes is a nightmare. I agree with you that though some studies suggest that caffeine consumption leads to excessive dehydration, there are several others that suggest that this is just a misconception despite its diuretic effects. Caffeine increases the rate at which the kidneys eliminate sodium and water but does not influence the rate at which the body retains fluid (Killer et. al, 2014). One cup of coffee is a diuretic and, in some cases, may have no impact on urinary out, but so is a cup of caffeinated tea. The kidneys control the balance between water, sodium, and potassium. Caffeine is basically a mild stimulant that increases the amount of potassium in the urine, which can eliminate sodium, and water, and allow one to drink more, hence staying hydrated.
ReplyDeleteKiller, S. C., Blannin, A. K., & Jeukendrup, A. E. (2014). No evidence of dehydration with moderate daily coffee intake: a counterbalanced cross-over study in a free-living population. PloS one, 9(1), e84154. https://doi.org/10.1371/journal.pone.0084154
This is a very interesting topic! especially since in our day so many people drink coffee. I never really thought about caffeine dehydrating you. It seems that coffee may effect the amount of electrolytes but does not necessarily influence fluid retention (Armstrong, 2002). In one study, they actually found that having a tolerance to caffeine could actually reduce the likelihood of someone undergoing a detrimental fluid-electrolyte imbalance (Armstrong, 2002). Caffeine has a lot of health benefits under normal levels of intake. Your post got me thinking about how I was always was told that having more than 1 or 2 cups of coffee a day (or caffeine in general) was too much, so I assumed all the health benefits were lost after this number. I found another article on pubmed that opposes what I've always been told. Although there is a range of consumption correlated with health benefits, The largest risk reduction in cardiovascular problems was seen at 3-4 cups a day, and more likely to benefit health than harm. (Poole et al. 2017). This is anywhere between 250-350 mg of caffeine, which is quite a bit!
ReplyDeletePoole R, Kennedy OJ, Roderick P, Fallowfield JA, Hayes PC, Parkes J. Coffee consumption and health: umbrella review of meta-analyses of multiple health outcomes. BMJ. 2017 Nov 22;359:j5024. doi: 10.1136/bmj.j5024. Erratum in: BMJ. 2018 Jan 12;360:k194. PMID: 29167102; PMCID: PMC5696634.
Armstrong LE. Caffeine, body fluid-electrolyte balance, and exercise performance. Int J Sport Nutr Exerc Metab. 2002 Jun;12(2):189-206. doi: 10.1123/ijsnem.12.2.189. PMID: 12187618.