Question: I have read conflicting things about whether caffeinated and alcoholic beverages should "count" in the daily water intake recommended by my diet. Do you have any input on this?
Answer: It used to be thought that caffeinated beverages would dehydrate a person to the point where the water in them "wouldn't count." However, multiple studies have shown that the amount of caffeine in most popular beverages does not keep the body from absorbing the water in them. Therefore, from the standpoint of hydration, caffeinated beverages can count towards the total.
Alcoholic beverages are a different story, however. Alcohol increases urination fairly dramatically. Depending upon the alcohol concentration of the drink, it could even cause you to eliminate more water than the drink contains. So alcoholic beverages should not count towards the total fluid intake, and you might even want to have an extra glass of water.
Beyond this, any fluid allowed by your diet can count toward your total fluid intake, but plain water is usually preferred. Alternatives to Plain Water
Source: (there are many similar studies):
Armstrong, LE. "Caffeine, body fluid-electrolyte balance, and exercise performance." Int J Sport Nutr Exerc Metab. 12/2 2002.
