 For years I've recommended that the healthiest beverage to drink is tea. Even healthier than water, since tea is all the water of water, yet as a bonus carries a huge load of nutrition without adding calories. But there's a belief that caffeinated drinks, such as tea, may adversely affect hydration. Now this was based on experiments done with high-dose caffeine pills, though, which may not entirely reflect the likely impact of tea, which is a more complex substance. So researchers compared 4 cups of black tea to 4 cups of water and 6 cups of black tea to 6 cups of water. Kept volunteers locked up for 24 hours, so could measure every drop going in and every drop coming out. The test revealed no significant differences between tea and water. For any of the average blood or urine measurements, it was concluded that black tea in the amount studied offered similar hydrating properties to water. Thus, tea could be considered a healthy choice of beverages and health professionals that don't know any better and incorrectly identify tea as a diuretic could be misleading people and serve to drive consumption towards less healthy beverages.