Despite what you may think, a new study shows that moderate coffee consumption does not cause people to become dehydrated. This research was conducted to the Institute for Scientific Information on Coffee.
The study involved having 50 men drink four mugs of black coffee or four mugs of water each day for three days. After a 10 day “wash out” period, the men swapped beverages and tried the other. University of Birmingham School of Sport and Exercise Sciences researchers analyzed the hydration status of the participants after both the water and coffee drinking periods by looking at their total body water and body mass. There were no significant differences between either group, and there were also no differences in urine volume or concentration.
Researchers conducted the study to evaluate the persistent myth that coffee causes dehydration because caffeine can act as a diuretic, and that past research had been inconclusive. The Mayo Clinic has pointed out in the past that normal consumption of caffeinated drinks can actually contribute to daily fluid requirements!