The analysis of several studies on caffeine and how it affects the body's hydration levels reveals that coffee may not be the evil dehydrator we always thought it was! From tracking the diuretic effect of caffeine intake to measuring hydration levels before and after caffeine consumption, scientists are experimenting with the theory that drinking coffee may not be a root cause for excessive dehydration.
For example, athletes -- who are at particular risk of dehydration and decreased electrolyte balance due to their high energy workouts -- were historically warned away from caffeine intake because the mild diuretic effect was considered to exacerbate this condition. However, new studies are indicating this assumption is erroneous, revealing no measurable increase in dehydration from caffeine intake before or after exercise.
Additionally, an extensive review paper published in 2007 even indicated that caffeinated fluids can be included in the daily fluid intake requirement for most people and that it served to provide the same re-hydration effect as pure water.