Does Coffee Dehydrate You?

Coffee pour

Verywell / Jiaqi Zhou

Drinking coffee is ritualistic for many. It’s part of life, deeply ingrained within people's routines, and often necessary for some. We drink coffee to feel alert, to feel comforted, to feel human. Coffee can help us work faster and workout harder. It can keep us awake after a restless night and keep mood swings at bay. 

If you're a coffee drinker, you might be wondering if coffee is dehydrating you and whether you should be drinking water to compensate for your coffee drinking.

Does Coffee Really Dehydrate You?

Many people believe coffee contributes to dehydration. This belief stems from a very small but very influential study published in 1928. In the decades since, “coffee dehydrates you” has become a sort of conventional wisdom that percolates (pun intended) as fact. 

The 1928 study found that people who drank coffee or caffeinated tea urinated up to 50 percent more than people who didn’t drink those beverages.

What people failed to interpret, however, was that the authors also hypothesized that regular coffee consumption could result in a tolerance effect—meaning people who drink coffee often won’t experience a significant diuretic effect. 

Later studies confirmed that hypothesis time and time again: 

  • A 2002 review of studies concludes there is a “profound tolerance” to diuresis in regular coffee drinkers and there is “no support for the suggestion that consumption of caffeine-containing beverages as part of a normal lifestyle leads to fluid loss.
  • An individual 2002 study on caffeine and exercise performance found that coffee and other caffeinated beverages won’t cause detrimental imbalances in electrolytes (electrolyte balance is a key factor in hydration).
  • A 2014 meta-analysis concludes there’s no risk of dehydration when drinking caffeinated beverages before exercise.
  • A 2014 study found that caffeine does not affect fluid balance or hydration status in healthy adults who regularly drink coffee.
  • One 2017 study found that coffee with higher caffeine content is more likely to affect electrolyte balance than coffee with lower caffeine content.

Coffee Doesn't Dehydrate You

Despite persistent and common belief, research doesn't support the claim that coffee dehydrates you.

What Is a Diuretic Anyway?

A diuretic is a substance or compound that causes your body to produce more urine than it normally would under given circumstances. Some people take diuretics as medications to help with conditions like high blood pressure or edema (fluid buildup).

Diuretics also occur naturally in some foods and drinks, including coffee and alcohol. Some herbs and spices, such as black cumin, and dandelion, are also thought to have diuretic properties.

How Coffee Works as a Diuretic

Coffee’s diuretic effect comes from the caffeine content in coffee. When you drink coffee, caffeine passes from your digestive tract into your bloodstream, where it works its magic.

Your body breaks caffeine down into compounds that affect how your organs, including your brain, work.

In addition to its effects on the brain, caffeine also causes your kidneys to produce more urine, flushing more sodium and water from your body. However, research shows the effect is mild and short-lived. It’s also not as strong in regular coffee drinkers.

Does Coffee Contribute to Your Water Intake? 

When you drink coffee, you’re consuming ample water along with the caffeine and other compounds in coffee. In most cases, the water consumption negates the diuretic effect of caffeine, especially in habitual coffee drinkers.

Like one study suggests, it’s likely that the higher the caffeine content in a cup of coffee, the less hydrating it is overall. Other research suggests the caffeine content in coffee doesn’t affect water balance in people who drink coffee every day.

All in all, research suggests your daily cup of coffee can actually help you reach your fluid intake goals, not take away from them. If you’ve ever been worried that your favorite morning beverage was dehydrating you, you can now fully enjoy it without concern. However, while coffee does contribute to fluid intake goals, water is still the best choice for proper hydration and should not be replaced by coffee.

Coffee and Fitness

Coffee has long been studied for its potential performance-enhancing effects. In addition to helping you get through morning grogginess, coffee may also help you push through a grueling workout.

Coffee May Be an Excellent Pre-Workout Beverage

Because of its caffeine content, coffee is a great pre-workout beverage that can give you a mental and physical boost without the unwanted side effects that come with many pre-workout powders. (And no, it won't affect your hydration status during exercise if you drink it prior to your workout).

Coffee may boost your fat-burning potential in addition to increasing your energy and mental focus. Combined, those three effects of coffee can give you a serious edge during your workouts. 

Just remember that you can build up a tolerance to caffeine like you can any other stimulant. If you drink coffee as a pre-workout supplement, you may find yourself needing more and more to get the same effect. Just be sure to keep your caffeine intake below 400 mg per day which is the recommended limit for most healthy adults.

Individual Responses to Coffee

Many people love their morning coffee and experience nothing but pleasant effects from a steaming cup of brew. However, other people experience unpleasant side effects from coffee. Headaches, dizziness, nausea, jitteriness and nervousness can all set in after drinking caffeinated coffee, especially for those who don’t regularly consume caffeinated beverages.

Some people also experience a post-coffee crash once the stimulating effects of caffeine wear off. 

Only you know how your body responds to caffeine. If you experience adverse effects in response to caffeine, it’s probably best to avoid caffeinated beverages. Luckily, decaf coffee is widely available at grocery stores and supermarkets, so you can still enjoy the taste and ritual of coffee. 

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