Bodybuilders can only digest 50 grams of protein at one sitting?  Remember that one?  For years this rumor floated around the bodybuilding community but had no scientific basis to support it.  You need to drink 8 glasses (8 oz. each) of water everyday for optimal health-not including caffeinated and alcoholic beverages..  Many bodybuilders often carry consume a gallon of water a day.  Researchers from the Renal, Electrolyte, and Hypertension Division at the University of Pennsylvania claim that there is no scientific evidence to support these claims.  Where did this claim come from questioned the scientists writing the review?  Another popular idea found on Internet sites is that ingested water is retained in various organs and improves their function. The review article mentioned one study where 14 individuals in "good health" suggested that water retention is quite variable and depends significantly on the speed with which water is ingested. A water load ingested over 15 min is largely excreted, whereas a water load ingested over 2.5 h is largely retained. To summarize the conclusions of other, more exhaustive reviews: There is no clear evidence of benefit from drinking increased amounts of water; however they also concluded that there is also no clear evidence of lack of benefit.

Negoianu D, Goldfarb S. Just Add Water. J Am Soc Nephrol. 2008 Apr 2;