Coffee Dehydrates You. Science calls BS.

Lets start with a little info on the mysterious and sometimes illusive creator of life: Water.

urine-color-chart-2-2Every single cell in the human body needs water to function properly. In fact, water is your body’s principal chemical component and makes up about 60 percent of your body weight. We need water to regulate our temperature, to cushion and protect joints and organs, and to help digestion move smoothly.  With the goal of getting at least 64oz (1.9 liters) of water a day, we need to be as efficient as possible because a lack of water can lead to dehydration. Even mild dehydration can drain your energy, make you tired and affect performance which is the direct opposite of why we drink coffee.

Science once again says that coffee is awesome.


Researchers at the University of Birmingham School of Sport and Exercise Sciences, studied the effects of moderate coffee consumption, and consumption of equal amounts of water on 50 male participants. The men were asked to drink either four mugs of black coffee or water for three days in the first phase of the study, then drink the opposite for three days in the second phase. The phases were separated by a 10 day “wash out” period.  The subjects’ body mass and total body water, blood and urine were analyzed. No link between moderate coffee consumption and dehydration were found. 

A study on the diuretic effects of caffeine, by a scientist at the University of Connecticut, appeared in The International Journal of Sports Nutrition and Exercise Metabolism. Based on a review of 10 scientific research studies, the scientist concluded that when coffee or a caffeinated beverage is consumed, the body retains some of the fluid and that caffeine consumption causes a mild diuresis that is very similar to the diuretic actions of water.

Another study, reported in the same journal, involved research scientists studying 59 active adults over an 11-day span while controlling their caffeine intake. The participants in the study were given caffeine pills on some days and on other days were given a placebo pill. They found that there was no evidence for dehydration or fluid status changes based on no significant differences in levels of electrolytes or total urine volume.

 In addition to not dehydrating you, results showed the coffee actually contributed to a person’s daily fluid requirements.  While caffeine is dehydrating, the water in coffee more than makes up for the effects, ultimately leaving you more hydrated than you were.   Your body, being the adaptable miracle that is, can actually adjust to coffee when consumed regularly, and it will no longer have a diuretic effect.


The take-home point here is that coffee and caffeine consumption in moderation can have a mild diuretic effect.  Essentially, if you drink a liquid, especially if you drink 3 or 4 cups of a liquid, you’re going to urinate a lot no matter what it is you’ve consumed. There is no proven evidence that coffee leeches the body of electrolytes, sodium, potassium or causes significant dehydration.   So the next time you go on a road trip, don’t blame the coffee for your baby blatter.


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