It’s often said that drinking coffee cause dehydration but is this claim true? Before we can answer this question we need to run through some basic stuff.

Caffeine is the main ingredient responsible for the stimulating effect of coffee, it’s the most psychoactive drug consumed worldwide. When we wake up, a chemical substance called adenosine start building up in the central nervous system and it’s responsible for the drowsiness and fatigue throughout the day, Caffeine is actually an antagonist and it blocks adenosine receptors giving you that feeling of energy and increasing your attention.

A diuretic effect is the increase of urination caused by many substances called diuretics.They can be the treatment for many conditions such as high blood pressure, cardiac failure,etc..Diuretics generally block sodium and water reabsorption in the kidney more specifically in the proximal part of the tubuli thus increasing the final urine output. In fact each family of diuretics has its own mechanism as shown below.

I will write a post about the subject in the future so stay tuned if you have any questions.

Source: Wikimedia

Back to our subject,many people believe that coffee causes dehydration even some scientists,they claim that caffeine has diuretic effects.Actually,the original idea that caffeine can cause dehydration can be traced to a study in 1928 that noted increased urination in people who drank caffeinated beverages.

So if this is true than why we don’t become dehydrated when we drink coffee ? well they think that in order to have a significant level of dehydration,we need higher doses.

Many studies were dedicated to this subject,the most important one is a research by Professor Lawrence Armstrong in 2005.

One group was given a placebo and 59 healthy males were given caffeine supplements for 11 days and have their diets under control,the scientists  mesured their hydration levels through 20 biological markers including creatinine levels,urine output and electrolyte balance.It was the first to evaluate caffeine consumption for a continuous period longer than 24 hours.The results showed no difference in the hydration levels of the two groups, all their biomarkers were normal.Pr Armstrong finally put the myth to rest..

Another study published in the journal of human nutrition and dietetics in 2003 found the same results,absolutly no dehydration..

When you drink 3 or 4  cups of coffee a day,you increase the amount of water in your body so it’s perfectly normal to urinate more than usual.Drinking excessive amounts of juice makes you urinate but is this because juice has diuretic effects ? absolutely not ! the claim is totally a myth and has no scientific basis behind it.

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References & Sources:

https://www.ncbi.nlm.nih.gov/pubmed/19774754

https://www.livescience.com/55479-does-caffeine-cause-dehydration.html

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3886980/

https://www.trainingpeaks.com/blog/does-coffee-really-dehydrate-you/

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