What does diuretic mean?

Perhaps, first of all though, we should clarify what diuretic means. It is defined as:

“…causing increased passing of urine”...

...which is from the Old French word, diuretique, and via the ancient Greek, diourētikos.

Does Coffee Dehydrate You?

Coffee with caffeine is seen as being a dieuretic, meaning that it promotes the formation of urine by the kidney.

But, actually, caffeine is not a strong diuretic - it's a fairly mild diuretic.

Indeed, it takes more than just one cup for caffeinated coffee to have an effect on the body. Most likely only 2 cups of caffeinated coffee starts having a diuretic effect.

Studies show it takes as much as 360 milligrams of caffeine to act as a diuretic.

To put that into perspective, a typical 8-ounce cup of coffee has 95 to 200 milligrams of caffeine, depending on the brew.

Yes, regular caffeinated coffee is a diuretic. This means it can increase the production of urine, thereby promoting the loss of water from the body. The diuretic effect of coffee is primarily due to its caffeine content. Caffeine can increase blood flow to the kidneys, which in turn encourages them to release more water.

However, it's important to note that the diuretic effect of coffee can vary from person to person, depending on their tolerance to caffeine and how much coffee they consume. For individuals who regularly consume caffeine, the body can develop a tolerance, and the diuretic effect may be less pronounced.

For occasional coffee drinkers or those who consume it in large amounts, the diuretic effect might be more noticeable. It's always advisable to balance coffee intake with adequate water consumption to maintain hydration levels, especially for those who are sensitive to the effects of caffeine.

Is decaf coffee a diuretic?

The answer is no. Decaf coffee is not a diuretic.

However, it must be stressed that decaffeinated coffee has no diuretic effects and is an excellent way to hydrate during the day.

So, decaf coffee is not a diuretic.

It is about equal to water in how much it makes a person urinate. Decaffeinated coffee is also an excellent source of antioxidants like its cousin – regular coffee.

But, even about coffee with caffeine, the conventional view of coffee as a diuretic is changing and, in moderation, coffee can actually be counted as part of your hydration for the day.

Indeed, the latest U.S. dietary guidelines increased the limit on caffeine to 400 mg a day in adults and it’s now noted as an excellent source of potassium and magnesium, as well as one of the top sources of daily intake of antioxidants – for both decaf and regular coffee

A recent study carried out by researchers from the School of Sport and Exercise Sciences at the University of Birmingham went as follows:

 50 healthy men (aged 18 to 46) with stable weight, diet and fluid intake were chosen. Women were said to be excluded due to possible fluid balance changes caused by the menstrual cycle.

All participants in the study were described as moderate coffee drinkers consuming between three and six cups per day (300 to 600mg/day caffeine).

As part of the study, on two separate occasions, each man drank four, 200ml cups of black coffee per day for three days (providing 4mg/kg of caffeine per day), or three cups of water per day for four days.

During each trial period the participants drank a regulated amount of water provided in bottles, the amount of which was determined for each of them based on their three-day food diary.

During the water-only trial, they were drinking four extra cups of water a day.

During each trial period the participants also did no physical activity, did not drink alcohol and ate a controlled diet as provided by the researchers in order to limit the effects of these factors on their overall hydration.

The two trial periods were separated by a 10 day wash-out period when the person resumed their normal caffeine intake, diet and activity.

Then, before and after each trial, the researchers measured total body water, body mass and blood, urinary markers of hydration (such as sodium, potassium and creatinine levels) and blood analysed for caffeine levels to confirm compliance.

The results from the study was as follows:

  • The researchers found no significant difference in total body water from before and after each trial and there was also no significant difference in total body weight between the two trials.
  • Nor was there any differences between the two trials in blood markers or urinary markers of hydration, or 24 hour urine volume.
  • Urinary sodium levels were found to be higher during the coffee days most likely because caffeine increases kidney excretion of sodium, however, they found no difference in other measures of hydration or urine output and there were no significant differences in body mass between the two trials, though there was a small gradual daily fall in body mass in both trials.
  • The study concluded that “coffee, when consumed in moderation by caffeine habituated males[,] provides similar hydrating qualities to water”.

This was a small study, however, and more research needs to be done on the effects of caffeine on hydration and sodium levels of the body. But, it does muddy the waters of the old traditional view that caffeine is a diuretic.

Increasingly, it is being seen as part of part of the consumer’s mix of beverages. Regular coffee is certainly the lesser of two evils if we compare the many “energy” drinks and soft drinks on the market with high levels of sugar and artificial ingredients.

Having said of all that, decaffeinated coffee should definitely be considered since it has no diuretic effects and is an excellent way to hydrate during the day.

Decaf coffee is also an excellent source of antioxidants like its cousin – regular coffee.

How does the body develop a tolerance to caffeine and over what time frame can this occur?

The development of caffeine tolerance in the body is a complex process influenced by several factors including the frequency and amount of caffeine consumed.

Tolerance to caffeine can develop relatively quickly, often within a few days to a week of regular consumption. This adaptation results from the body's neurochemical response to caffeine, which blocks adenosine receptors, leading to reduced sensitivity over time.

As tolerance increases, individuals may find that they require larger amounts of caffeine to achieve the same stimulating effects, including its diuretic properties.

Are there differences in hydration effects or diuretic properties between different types of caffeinated beverages such as tea, energy drinks, or soft drinks, compared to coffee?

Regarding the differences in hydration effects between various caffeinated beverages and coffee, the impact on hydration can vary due to the caffeine content and other ingredients.

For example, tea generally contains less caffeine than coffee, potentially making its diuretic effect less pronounced.

Energy drinks and soft drinks, on the other hand, not only contain caffeine but also high levels of sugar and other substances that can affect hydration and overall health differently.

The sugar content, in particular, may contribute to quicker fluid loss or changes in blood sugar levels, which can influence hydration status indirectly.

What are the potential health implications of the higher urinary sodium levels observed during the coffee consumption days in the study?

The observation of higher urinary sodium levels during days when coffee is consumed points to caffeine's role in promoting sodium excretion through the kidneys.

While this effect can help prevent fluid retention, it might also have implications for individuals with health conditions sensitive to sodium balance, such as hypertension or heart disease.

In such cases, increased sodium excretion could potentially affect blood pressure control and cardiovascular health, although the impact would depend on the overall diet and health status of the individual. It's essential for people with these conditions to monitor their caffeine intake and consult healthcare professionals regarding their diet and hydration strategies.

IMPORTANT: This information is intended to support, not replace, discussion with your doctor or healthcare professionals. Nothing in the content or products should be considered, or used as a substitute for, medical advice, diagnosis or treatment. You should always talk to your health care provider for diagnosis and treatment, including your specific medical needs.

January 08, 2017 — Guy Wilmot


Bluesmama1012 said:

This is not true. One cup of decaf makes me pee every 30 minutes and my urine stings. The urologist said all coffee has acid and this can also cause it. You guys had better do a fact check.

Joe Strauss said:

Same. Decaf coffee has a strong effect. Regular coffee, not at all. I think there’s some residual left in the decaf that is causing this.

Luckythedog said:

Decaffeinated coffee has a diuretic effect upon me.

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