While a steaming cup of coffee is probably not the first thing you would reach for after you cross the finish line of a marathon, it wouldn’t be the worst beverage choice. Coffee and tea often get a bad rap when it comes to hydration, but both—as well as other caffeinated beverages—can help us stay hydrated throughout the day.
According to a 2004 National Academies of Sciences, Engineering, and Medicine report titled Dietary Reference Intake: Water, Potassium, Sodium, Chloride and Sulfate, “about 80 percent of people’s total water intake comes from drinking water and beverages—including caffeinated beverages—and the other 20 percent is derived from food.” The report goes on to suggest that women consume an average of 2.7 liters (91 ounces) of total water—from all beverages and foods—each day, and men an average of 3.7 liters (125 ounces) of total water daily.
Let’s conduct a brief review of hydration. A person is considered hydrated when the amount of fluid coming into their body is balanced with the amount going out. Every person has a different amount of fluid they need daily to meet their hydration needs, so it’s often difficult to offer a blanket recommendation. While eight 8-ounce cups daily are common advice and easy to remember, that suggested intake may not represent precisely what each person needs. In fact, the best way to know your hydration status is simply to look at the color of your urine. Pale yellow urine or clear urine typically indicates adequate hydration, while dark yellow or brown urine means a person isn’t getting quite enough fluid. Water, milk, juice, and other beverages, as well as juicy foods like fruits, all contribute to overall water intake. There is often confusion around coffee and tea since caffeine is classified as a diuretic, but both beverages can be hydrating.
A diuretic is a substance that stimulates fluid loss by means of urination, sweating, or breathing out water vapor, which leads many to think that coffee and tea would dehydrate a person rather than the opposite. Someone who drinks coffee or tea daily can likely attest to the need to use the restroom shortly after finishing their first cup. However, it’s a myth that caffeinated beverages are dehydrating due to their diuretic effect. Coffee and tea do contain varying levels of caffeine, but it’s important to note that they both are mostly water and therefore can be hydrating. While many may suspect that a standard cup of coffee every morning might contribute to dehydration, the amount of water in the drink is hydrating.
Does that mean coffee can hydrate just as well as water?
There’s a reason water is recommended by so many doctors, nurses, dietitians and other healthcare professionals: It’s hydrating without anything extra added to it. There’s no added sugar, proteins, or additives and ingredients like sweeteners or caffeine that might affect its absorption and metabolism. While water is seen as the best source of hydration, it’s not the only one. Beverages like coffee and tea can have their place in our daily hydration routines, too. Studies are inconsistent on whether or not caffeinated drinks like coffee have similar hydrating effects to water. In general, though, coffee and tea provide hydration, and the diuretic effect of the caffeine will depend on individual factors such as activity level, tolerance to caffeine, and other foods and beverages consumed.
Don’t replace that glass of water with a cup of coffee so quickly.
While coffee and tea do contribute to an individual’s hydration levels, their amount of caffeine can impact the body at certain levels. The current caffeine recommendation for most adults is no more than 400 milligrams per day, which is about equivalent to three to four eight-ounce cups of coffee or eight cups of black tea. For certain populations, like pregnant or lactating women, the recommendation is lower, at 200 milligrams per day.
While many adults can easily hit the 400-milligram threshold without a minor tremor of the hands, others may not be able to finish a single cup of coffee in the morning. A person’s tolerance level to caffeine depends on how frequently and how much caffeine they consistently consume. The diuretic effect is also thought to be related to individual tolerance. Caffeine may cause higher urine output in individuals who have not had caffeine for several weeks or months as compared with those who drink caffeinated beverages at least daily.
The Bottom Line
Coffee and tea are much more than just their caffeine content—they’re mostly water after all. Water alone comes with a plethora of benefits, but it doesn’t have to be the sole source of hydration. If you find yourself drifting at your desk on a Monday afternoon, coffee and tea are not only great pick-me-ups because of their caffeine content, but they can also keep you well hydrated.
This article was written by Courtney Schupp, MPH, RD.
- Food Insight, Pore Over What Drinking Only Coffee and Tea all Day Does to Your Body, 2018
- Food Insight, Everything You Need to Know About Caffeine, 2015
- IFIC Foundation, Sources and Amounts, 2020
- IFIC Foundation Caffeine and You, 2020
- Journal of Human Nutrition and Dietetics, Caffeine Ingestion and Fluid Imbalance, 2003
- The Centers for Disease Control and Prevention (CDC), Drinking Water and Water Intake, 2016
- The National Academies of Sciences, Engineering, and Medicine, Dietary Reference Intake: Water, Potassium, Sodium, Chloride and Sulfate, 2004
- U.S. National Library of Medicine, National Institutes of Health, No Evidence of Dehydration with Moderate Daily Coffee Intake: A Counterbalanced Cross-over Study in a Free-Living Population, 2014
- U.S. National Library of Medicine, National Institutes of Health, Caffeine Ingestion and Fluid Balance, 2003