Coffee is one of the most popular beverages in the world.
A major reason why people drink coffee is for its caffeine, a psychoactive substance that helps you stay alert and aids performance.
However, caffeine can be dehydrating, which may make you wonder whether drinking coffee hydrates or dehydrates you.
Caffeine is 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.
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.
You need to consume at least 5 cups of coffee daily for it to cause dehydration. 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.
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. To sum it up, moderation is key.