The Myth That Just Won't Die: Drink 8 glasses of water a day for good health (the '8 x 8' rule)

Everyone has heard the maxim that one must drink 8 ounces of water 8 times a day. Problem is that it simply isn't true. Not only that, but it was debunked in 2002 and yet it is still passed around as gospel.

It started sometime in the 80s, and without any scientific support it became a physical fitness mantra. People would even boast about how much water they drank as they carried around their water in a variety of containers.

At best, drinking this much water is harmless and just increases the number of bathroom trips that one needs to take. At its worse however it can cause or exacerbate medical problems such as the dilution of sodium in the body also known as "hyponatremia."

Even modest increases in fluid intake can result in 'water intoxication' if one's kidneys are unable to excrete enough water (urine). Such instances are not unheard of, and they have led to mental confusion and even death in athletes, in teenagers after ingesting the recreational drug Ecstasy, and in ordinary patients.

And he [Dartmouth DMS physician Heinz Valtin] lists other disadvantages of a high water intake: (a) possible exposure to pollutants, especially if sustained over many years; (b) frequent urination, which can be both inconvenient and embarrassing; (c) expense, for those who satisfy the 8 x 8 requirements with bottled water; and (d) feelings of guilt for not achieving 8 x 8.

Of course people do need water and we need to replace what we lose and these recommendations exclude special circumstances, such as strenuous physical activity, long airplane flights or hot weather. But under normal circumstances much of our water intake comes from the consumption of nearly all foods — fruit, meat, dairy, breads, everything except dried foods. Finally, contrary to water advocates, moderate consumption of beer and coffee count as well. The diuretic effects of these drinks has been greatly exaggerated.

While we are busting water consumption myths, here's one more. By the time you are thirsty, it's too late. On the contrary, most experts would define dehydration as beginning when that concentration has risen by at least five percent yet thirst begins when the concentration of blood has risen by less than two percent.

Dr. Valtin, who is quoted above, and did the original research debunking the 8x8 rule, noted that it's "difficult to believe that evolution left us with a chronic water deficit that needs to be compensated by forcing a high fluid intake."

So when you should drink? When you are thirsty is a good place to start.