Coffee is known to have a diuretic effect. Since it causes the body to excrete more fluids than the amount consumed, there are claims that excessive intake can lead to dehydration. Is this true? Let's examine the research findings.

 

The principle by which caffeine in coffee induces diuretic effects is as follows: caffeine binds to adenosine receptors instead of adenosine. This causes the blood vessels in the kidneys to dilate and promotes the excretion of sodium and water, resulting in an increased volume of urine. Additionally, caffeine inhibits the action of the antidiuretic hormone vasopressin, further increasing urine output, and stimulates the bladder detrusor muscle, leading to the sensation of needing to urinate even when the bladder is not full.

 

However, the water loss caused by caffeine is not enough to cause dehydration. There are also research findings indicating that coffee consumption does not increase water excretion. In 2014, a research team from the University of Birmingham in the UK conducted a study where 50 men were divided into two groups for three days: one group consumed four cups of coffee containing 4 mg of caffeine per kilogram of body weight daily, and the other group only drank water. The study analyzed the body's water content. The results showed no difference in body water levels between the two groups. No significant differences were found in hematological indicators, 24-hour urine volume, or creatinine levels. However, the sodium content in urine was higher in the coffee-consuming group compared to the water-only group.

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There are also research findings indicating that drinking caffeine before and after exercise does not pose a problem. In a study published in the SAJSM in 2014, the research team divided eight healthy college students into four groups: one that consumed both caffeine and fluids before and after exercise, one that only consumed caffeine, one that only consumed fluids, and one that consumed neither. They then measured physical changes. The results showed that consuming approximately 460 mg of caffeine did not affect urine volume or body water content after exercise.

 

So, what about people with sensitive bladders? According to a study published in the journal 'Urology Annals' in 2011, individuals with overactive bladders did not experience any particular problems when consuming small amounts of caffeine. However, when intake exceeded 4.5 mg per kilogram of body weight, the bladder nerves were stimulated, and blood flow to the kidneys increased, leading to an increase in urine volume. In other words, a 60 kg man with a sensitive bladder who drinks two cups of American coffee may experience an increase in urine volume. A single cup of American coffee containing two shots of espresso has about 150 mg of caffeine.

 

The recommended daily caffeine intake for adults in South Korea is less than 400mg. As long as this amount is maintained, there is no significant concern for physical health due to diuretic effects. However, it is advisable to be cautious with adolescents and children, as central nervous system stimulation can cause issues such as decreased concentration.

 

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Coffee contains 1.5 times the amount of water in the body.

This is coming out much more than I expected.

 

So, after drinking coffee, you should drink about twice as much water.

It seems the reason is here.

 

The daily water intake is when you drink coffee.

Should I consume a bit more?