Does Coffee Make You Dehydrated?

does coffee make you dehydrated
I drink a lot of coffee and have done so for years. These days I drink less coffee in terms of volume than ever before but the coffee I do drink is a bit more potent.

For a while my wife has been telling me that I need to drink other “non-coffee” drinks to stay hydrated but without going out with a purpose to do so I’ve always done pretty good.

I can’t help but recognize the fact that drinking large volumes of coffee almost always means I’m going to have to go pee in the next couple hours but I’m not 100% sure this is due to the diuretic effect of the caffeine or because of the quantity of fluids I’m taking in.

In fact lately as I’ve been drinking a lot of espresso and potent french press coffee I’ve probably been going pee less frequently than before. Even though I’m drinking more caffeine per ounce of fluid I’m not experiencing the same diuretic effect so this led me to this small blurb posted by the Mayo Clinic’s Katherine Zeratsky.

She writes:

“Drinking caffeine-containing beverages as part of a normal lifestyle doesn’t cause fluid loss in excess of the volume ingested. While caffeinated drinks may have a mild diuretic effect — meaning that they may cause the need to urinate — they don’t appear to increase the risk of dehydration.” Source

This kind of answers my question – If coffee is a diuretic then why do I not ever seem to get dehydrated while drinking it?

Looks like the water content in coffee offsets the fluid loss caused by an increased need to urinate after drinking coffee. In short it’s a wash.

My wife however still has hesitations in agreeing with this though so I have to dig deeper.

Does Coffee Make You Dehydrated?

The idea that drinking coffee can dehydrate you had surfaced as early as 1928. The study published in The Journal of Pharmacology and Experimental Therapeutics noted an increase in urination among people who drank caffeinated beverages, coffee included. This study led to the belief that coffee was diuretic.

The so-called negative effects of coffee is often attributed to its caffeine content. Also found in tea, soda and chocolate, caffeine is a widely consumed substance in every country around the world. It is a known natural stimulant used to perk people up. It is a legal substance and unregulated. However, this famous substance is often attributed to bad health benefits, one of which is dehydration.

What is dehydration?

Dehydration occurs when more water and fluids are exiting the body than are entering the body. With about 75 percent of the body made up of water found inside cells, within blood vessels, and between cells, survival requires a rather sophisticated water management system. – WebMD

Good thing, our bodies have a natural alarm system, and our thirst mechanism tells us when we need to increase fluid intake. We lost water constantly throughout the day as we breathe, sweat, urinate, and defecate, we can replenish the water in our body by drinking fluids. The body can also shift water around to areas where it is more needed if dehydration begins to occur.

In most cases, dehydration can be easily managed by increasing your fluid intake. However, some cases of dehydration needs immediate medical attention.

Why do people experience dehydration?

Primarily, dehydration happens when we lack water in the body, lost too much water or both. Here are some medical conditions that may cause dehydration:

  • Diarrhea – the most common cause of dehydration and related deaths. The large intestine absorbs water from food matter, and diarrhea prevents this function, leading to dehydration.
  • Vomiting – leads to a loss of fluids and makes it difficult to replace water by drinking it.
  • Sweating – the body’s cooling mechanism releases a significant amount of water. Hot and humid weather and vigorous physical activity can further increase fluid loss from sweating.
  • Diabetes – high blood sugar levels cause increased urination and fluid loss.
  • Frequent urination – usually caused by uncontrolled diabetes, but also can be due to alcohol and medications such as diuretics, antihistamines, blood pressure medications, and anti-psychotics.
  • Burns – water seeps into damaged skin and the body loses fluids.

What do the Experts Say About It

In 2005, Lawrence Armstrong, a professor in the Department of Kinesiology at the University of Connecticut and director of the Human Performance Laboratory and his team of researchers analyzed whether drinking coffee can cause dehydration.

Armstrong’s study showed significant results because it covered beyond the 24-hour period. The study lasted for 11 days and significant data were gathered from the participants to indicate that drinking coffee is not the sole reason for dehydration.

In fact, the groups who took caffeine and the group that took placebo demonstrated hydration indicators like urine volume. The researchers were able to conclude that a higher dose of caffeine would not dehydrate a person nor smaller doses were.

In another report, BBC Health noted a study conducted by Sophie Killer at Birmingham University in the UK. She did not only measured the volume of urine, but tested their blood for signs of kidney function as well as calculating the total amount of water in the body. The men in the study drank four cups of coffee a day, far more than the average coffee-drinker. Yet there was no evidence they were any more dehydrated than those who drank water alone.

Another study published in PubMed, observed two groups of people who took increasing doses of caffeine for 11 days. The researchers did not notice a significant increase in urine volume of the caffeine group versus the non-caffeine group.

Why do Some People Think That Drinking Coffee Dehydrates Them?

  • Many people blame the caffeine. According to Armstrong, for a person to reach a coffee overdose, this person had to consume 10,000 milligrams of caffeine per day. An 8-ounce cup of brewed coffee has 95 milligrams of caffeine, on the average. To reach overdose and dehydration, one must have had 100 cups of coffee in a day.
  • Many people think drinking coffee causes frequent urination. A person can feel excessive urination after drinking coffee only if this person had been drinking coffee in succession and had no other liquid. By principle, our body will take in all kinds of fluids and process it, leaving the waste product to be carried out of the body through urine. Essentially, if you had been drinking coffee and had no other liquid intake, more likely, you will still be urinating as if you are drinking water.
  • Many people blame the temperature. The hot nature of coffee can trigger our body to perspire. This is especially true if you are drinking coffee during the summer days. Hot coffee adds to the increased temperature that you are already feeling. As a result, your body releases sweat to cool you down. If you drink coffee often during the summer, you will feel really dehydrated. What you can do is enjoy a cold brew instead of the usual hot brewed coffee.

Coffee, in itself, does not cause dehydration. There are several factors that come into play that causes body dehydration.


Head blogger at "Top Off My Coffee Please" and lover of great coffee.

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