Too Much or Not Enough?

Myth: You must drink eight 8-ounce glasses of water a day to maintain overall good health.

Reality: We have all heard that drinking eight glasses of water a day is essential for good health. Diet gurus, fitness fanatics, and fashion magazines all stress the importance of staying hydrated. The majority of us, however, rarely drink that much water on a daily basis. So, where did this belief originate from?

The recommendation to drink eight 8-ounce glasses of water a day (also known as 8x8) may stem from the following guideline posted by the Food and Nutrition Board of the National Research Council (NRC): “An ordinary standard for diverse persons is one (1) milliliter for each calorie of food. Most of this quantity is contained in prepared foods.”

Somehow, the second sentence was either forgotten or left out of the rumor-mill, so that the NRC’s guideline was inaccurately interpreted as eight glasses of water to be drunk each day. Kidney specialist and professor emeritus of physiology at Dartmouth Medical School, Hanover, NH, Heinz Valtin, MD, conducted research to uncover the validity of the 8x8 “rule.” What he learned from his research may surprise you:

• Dr. Valtin could find no scientific evidence to support the 8x8 water intake recommendation.
• Surveys of food and fluid intake conducted on thousands of adults of both genders suggest that such a large amount is unnecessary, because those surveyed were presumably healthy and not overtly ill.
• We consume a good portion of our water from the foods we eat like fruits and vegetables.
• Not all fluid intake needs to come in the form of plain water. Caffeinated drinks, and to a lesser extent diluted alcoholic beverages such as beer taken in moderation, may indeed be counted as part of your daily fluid intake.

(These conclusions apply to healthy adults in a temperate climate, leading a largely sedentary lifestyle.)

THE UPSIDE: Certain medical conditions, such as the treatment and prevention of kidney stones, require an increased water intake. It may also reduce the risk of other illnesses such as urinary tract infections, colorectal cancer, and fatal coronary heart disease.

THE DOWNSIDE: Drinking too much water may cause “water intoxication” which occurs when the kidney’s’ excretion of water (urine) cannot keep pace with fluid intake. It can also lead to mental confusion, seizures, and even death.

In conclusion, Dr. Valtin advices people should simply let their thirst guide their fluid intake unless there is a specific medical reason to do differently. Special circumstances, like strenuous physical activity, long airplane flights, and exposure to hot climates, may trigger the need for high water intake. For the majority of the population though, the 8x8 “rule” is nothing more than a myth.