Does Coffee Cause Dehydration?

We drink coffee to wake up in the morning and to keep going in the afternoon. We drink coffee because we like it. The wakeup part of coffee comes from caffeine which also acts as a diuretic. That is, caffeine causes your kidneys to produce more urine. So, if you drink lots of coffee does coffee cause dehydration? The quick, short answer is that if you drink lots of coffee that has lots of caffeine you will lose more water than you take in with the coffee.

Metabolism and Effects of Coffee

When you drink coffee, it passes into the intestinal tract and is absorbed into the blood stream. The many health antioxidants in coffee serve to decrease inflammation, reduce the likelihood of Type II diabetes, cut back on your chances of getting Alzheimer’s, and even decrease the risks of various cancers. Caffeine goes to the brain where it serves to wake us up and when it passes through the kidneys it stimulates increased urine formation. The direct effect of caffeine is that it increases blood flow to the kidneys which in turn ups urine creation. This effect has the potential to cause dehydration. Does it?

Making coffee with a French press coffee maker results in more oils and solids for a richer tasting coffee.
French Press Coffee Maker

How Much Coffee Does It Take to Cause Dehydration?

Coffee contains water so it should hydrate our bodies. Caffeine causes excessive urination which should cause dehydration. The key to the question of how much coffee it takes to dehydrate a person has to do with getting enough caffeine to overcome the water that one drinks with the coffee. Thus, stronger coffees are more likely to dehydrate than weaker ones and one needs to drink enough coffee to get enough caffeine to get the dehydration effect. How much is that? Studies have shown that a person of average size needs to ingest at least 500 mg of caffeine to get enough diuretic effect to overcome the amount of water they ingest with their coffee. Because an average cup of brewed coffee contains 90 mg of caffeine this means you need to drink more than five and a half cups of coffee a day to lose more water from your coffee drinking than you take in as part of the coffee.

Caffeine Content of Various Types of Coffee

Brewed coffee is the kind that most people drink. This includes using a percolator, pour over coffee, or a French press. The amount of caffeine in an eight ounce cup of brewed coffee ranges from seventy to one hundred forty milligrams with ninety milligrams being the average. Robusta coffee has a higher caffeine content than Arabica coffee from Colombia so you can drink more Colombian coffee than Death Wish coffee before you have to worry about dehydration.

Caffeine In Instant Coffee

Convenient instant coffee generally has less caffeine than brewed coffee ranging from thirty to ninety milligrams per eight ounce serving. So, if avoidance of dehydration is your only goal you can drink more instant coffee than brewed and accomplish your goal.

Caffeine In Espresso

A shot of espresso carries on average sixty-three milligrams of caffeine. Of course the volume of water is lower as well as thirty to fifty milliliters. However, the concentration of caffeine in espresso is as much as five times stronger than in brewed coffee.

Decaf coffee contains no more than seven milligrams of caffeine in an eight ounce cup so if your only goal is avoiding dehydration this is the next best step to drinking a glass of water!

You Need To Drink Lots of Strong Coffee To Achieve Dehydration

The bottom line to our question about dehydration is that you need to drink at least nine shots of espresso or about five and a half cups of brewed coffee for the amount of caffeine that you ingest to cause you to lose more water through your kidneys than you take in with the coffee. The amount of coffee goes down to around three cups a day if you are only drinking strong Robusta coffee.

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