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Does Coffee Dehydrate You? What The Experts Says

Coffee and dehydration

As you’ve sauntered into the break room for the day’s first cup of coffee, have you ever asked yourself whether coffee dehydrates you?

Have you thought of the recommended eight glasses of water a day and wondered if you’re getting enough fluids into your body? Does the coffee you’re drinking count as water?

Fluids are energy for our bodies and minds. I questioned whether the coffee-lovers of the world are truly getting the energy they desire in a healthy way.

There’s a Starbucks junkie in every circle, so read on to help educate yourself or a friend.


Caffeine is a natural substance found in dozens of plants, including coffee beans. People choose to consume caffeine because it jumpstarts the body’s central nervous system.

This jumpstart makes you feel more alert and ready to tackle everything from wrangling children to presenting a case in a court of law. Some people refer to caffeine as their “elixir of life” for this very reason.

There are some nasty side effects from too much caffeine: insomnia, high blood pressure, anxiety, and addiction, to name a few. One of the rumored side effects of drinking more than 400mg of caffeine a day can also be dehydration because coffee is a diuretic.

Is Coffee a Diuretic?

A diuretic is a substance that increases the need to urinate. Naturally, water is a diuretic, along with coffee and any other caffeinated beverages such as soda.

Studies (occurring as early as 1928 and again in 2005) show that caffeine is a weak diuretic. The human body will adjust to the regular intake of caffeine in 4-5 days, and you will no longer urinate excessively.

This means that regular caffeine consumption doesn’t lead to chronic dehydration. Coffee might be a diuretic at first, but those effects wear off quickly.

Lawrence Armstrong, who is a professor in the Department of Kinesiology at the University of Connecticut and director of the Human Performance Laboratory said that if you’re drinking more fluid of any kind, the amount of urine you produce will increase. “If you drink a liter of water, [urination] will increase…doesn’t mean you shouldn’t drink water.”

The study conducted in 1928 tested three people whose urine was compared before and after caffeine. After two months without any caffeine, the subjects received half a milligram of caffeine. The amount of urine produced was “noticeable” after they received the caffeine.

When given caffeine on a regular basis, the subjects had a less noticeable urine loss after 4-5 days. Armstrong and several other researchers conducted the updated study in 2005. This study involved a larger pool of subjects over an 11-day period, and confirmed the findings from the 1928 study.

Cutting Back on Caffeine Could Hurt More Than Help

Coffee adict

Some people feel the need to cut back on the amount of caffeine they drink. Commit to limiting your caffeine intake for good; cutting back on how much coffee you drink for only a short period could cause dehydration. As mentioned earlier, your body adjusts to your intake of caffeine after a few days.

If you reduce the amount of caffeine you’re drinking for a short period, your body will have to start the process of adjusting to your caffeine habits when you begin drinking more.

Bouncing back and forth between the amount of caffeine you take into your body is more harmful than committing to a regular daily or even weekly amount.

Dehydrated? Don’t Turn to Coffee

If you find yourself dehydrated, do not turn to caffeine to rehydrate yourself. Gulping down a coffee or caffeinated soda may seem like a tempting solution, since a lack of fluid causes fatigue. But, experts recommend avoiding caffeinated drinks when attempting to recover from dehydration.

The Bottom Line: Know Your Body

Studies have shown that various metabolisms react in different ways to coffee consumption. Your genetics might make you more tolerant to caffeine than others. It could also make you more sensitive and dehydrated. Measuring the human body’s hydration needs is a complicated process which most people do not have the time or the inclination to attempt.

Knowing what your body can handle is vital to answering the question of whether coffee dehydrates you. If you know your body can take that much caffeine, drink it. Ignore those disapproving looks as you swing by the break room for your fifth cup of the day.