Eight Glasses of Water Is Urban Legend

Q. When we ask how much water is healthy for us, the standard response is eight glasses of water per day. If someone had high blood pressure, could eight glasses of water per day be too much? I was thinking that since the first thing most doctors turn to for treating high blood pressure is a diuretic, maybe the problem is consuming too much water in the first place, as well as too much salt. Has there been any research on this?
A. There is surprisingly little research on the optimum amount of water most people should drink. Although it is a common belief that people need eight glasses daily, there is no scientific support for this idea (Journal of the American Society of Nephrology, June, 2008). The National Academy of Sciences recommends drinking when thirsty rather than consuming a specific number of glasses daily.
It is unlikely that drinking water raises blood pressure. A healthy body regulates fluids and electrolytes quickly. Although diuretics lower blood pressure, the exact mechanism remains mysterious (Journal of the Renin-Angiotensin-Aldosterone System, Dec. 2004).