Does Coffee Actually Dehydrate You?

Medically reviewed by Karina Tolentino, RD, CHWC

It's a widely held belief that coffee has dehydrating effects. But does coffee dehydrate you? Probably not. Studies show that it's unlikely for moderate coffee consumption to lead to dehydration.

Coffee's reputation for causing dehydration may stem from its mild diuretic effects or the dry mouth many coffee drinkers experience after their morning cup of joe.

This article explores the science behind coffee's diuretic effects and its impact on your body's hydration levels. It also explains why you might feel thirsty after drinking coffee and how to tell if you're dehydrated. 

Caffeine, Dehydration, and Diuretic Effects

Coffee contains caffeine, a natural stimulant that improves alertness, focus, and athletic performance. Caffeine is also a mild diuretic, which means it increases urine production. If you're peeing more frequently after drinking coffee, it's logical to assume this could lead to dehydration. However, research shows this is not the case—you take in more fluid by drinking a cup of coffee than you lose through urination.

Research suggests that, for habitual coffee drinkers, coffee is just as hydrating as water. It takes the body between one and four days to build a tolerance to the effects of caffeine, including its diuretic effect. So, regular coffee drinkers are less likely to experience increased urine output than those who drink the occasional cup of coffee. 

That doesn't necessarily mean you should reach for a caffeinated beverage whenever you feel thirsty. When it comes to caffeine consumption, moderation is key.

Consuming four or more cups of coffee daily—or more than 400 milligrams (mg) of caffeine—increases urine output for habitual and casual coffee drinkers, which may be mildly dehydrating. Research findings show that coffee containing high amounts of caffeine increases urine output (within two to three hours after ingestion) more than coffee containing lower amounts.

How Much Water Is in Coffee?

Coffee is mostly water. The water content in a cup of coffee can vary depending on the coffee bean type, degree of roast (light vs. dark), brewing method, and the coffee-to-water ratio. For example, a shot of espresso contains less water than drip coffee, and light-roast coffee beans tend to have higher concentrations of caffeine than dark-roast beans.

On average, water accounts for 98% of the total volume of the standard 6-ounce cup of brewed coffee. This means a 6-ounce cup of coffee contains about 5.88 ounces of water. Although coffee can contribute to your daily fluid intake, plain water is still your best bet for staying hydrated.

Why Does Coffee Cause Dry Mouth?

Contrary to popular belief, dry mouth after drinking coffee isn't due to dehydration. Coffee contains tannins—compounds responsible for coffee's bitter flavor and dry mouth effects. Tannins bind to proteins in saliva, making it thicker and less effective at lubricating your mouth, leading to a dry mouth sensation.

Can You Stop Coffee's Diuretic Effects?

If you're a regular coffee drinker and limit your intake to less than 400 mg of caffeine daily, coffee likely won't dehydrate you. But if you drink a lot of coffee and are concerned about hydration, you can offset any fluid loss and stay hydrated. Here's how:

• Choose coffee with a lower caffeine content: Caffeine is the substance in coffee that causes diuresis (increased urine output), so drinking coffee with a lower caffeine content can help reduce its diuretic effects. Decaf and half-caf coffee are good options. You can also brew your coffee at home, adding a smaller amount of coffee grounds per cup of water.

• Drink water throughout the day: Drink plenty of fluids to counteract the potential fluid loss from coffee. Water is the best choice for hydration, but you can also drink other liquids, such as milk, tea, and juice.

• Know your limits: If you're sensitive to caffeine or notice that you're peeing a lot more after drinking it, consider reducing your coffee intake or opting for lower-caffeine coffee options.

• Choose your coffee wisely: Some types of coffee contain more caffeine than others. Light-roast coffee beans generally contain slightly higher amounts of caffeine than dark-roast beans.

• Pace your consumption: Drinking multiple cups of strong coffee within a short period can intensify its diuretic effects. Aim to pace your daily consumption to avoid losing too much fluid.

Compared to Coffee, Is Tea More Hydrating?

Compared to coffee, tea is generally considered to be more hydrating because it contains less caffeine. Caffeine amounts in tea vary, depending on the type of tea, brewing method, and steeping time. Here's a breakdown of caffeine content per 8-ounce serving of coffee and tea:

Overall, tea is a good source of hydration, especially if you choose a tea with a low caffeine content, such as green tea or herbal tea. You can also reduce tea's caffeine content by steeping it for a shorter time.

How to Tell If You're Dehydrated

Dehydration occurs when your body loses more fluids than you consume. Signs and symptoms of dehydration include:

• Feeling thirsty

• Dark-colored urine

• Decreased urination

• Dry mouth and lips

• Headache

• Fatigue

• Dizziness or light-headedness

• Dry skin 
  

Causes of Dehydration

Coffee isn't likely to dehydrate you. However, factors that cause the body to lose fluids more quickly than you can replace them might. Common causes of dehydration include:

• Excessive sweating

• Vomiting

• Diarrhea

• Not drinking enough fluids

• Frequent urination (usually due to certain illnesses or medications)

Summary

Coffee contains caffeine, a stimulant with mild diuretic effects. You might notice you are peeing more frequently after drinking coffee, but the amount of fluid lost through urination is not enough to cause dehydration. 

Most people can safely enjoy coffee without having to worry about dehydration. Drinking more than four cups daily may increase the risk of mild dehydration. Drinking plenty of water throughout the day can mitigate the effects of caffeine and ensure you can enjoy your coffee beverages and stay hydrated.

If you are sensitive to the effects of caffeine and concerned about your hydration levels, consider drinking decaf coffee or tea, which is lower in caffeine and less likely to cause diuretic effects.

Read the original article on Verywell Health.