A number of patients coming into the office have sheepishly admitted that they don't drink enough during the day--water or otherwise. How much is "enough?"

The Journal of Physiology published this article, which attempted to review the extant evidence for or against the recommendation to drink at least eight 8 oz glasses of water per day. This recommendation is usually accompanied by the declaration that caffeinated beverages and alcohol don't count due to their diuretic effects. Though running into the problem of scant scientific articles, especially those evidence-based, this researcher concluded that for healthy men and women who lead realtively sedentary lives in temperate climates, the so called "8x8" recommendation has not been substantiated by scientific evidence. Note the qualifiers, though: the author acknowledges that adults who have significant disease or predisposition to certain diseases, who engage in vigorous work or exercise, or wholive in hot climates may indeed require 64 oz or more of water intake per day.

Other important points:

• using data from national and worldwide surveys, adequate water intake--via food, cafeinated beverages, and dilute alcoholic beverages (i.e., beer) in addition to water averages about five 8oz glasses per day
• individuals who may require "at least eight 8oz glasses of water" include those predisposed to kidney stones, leading active (more than walking for exercise) lives or living in hot climates
• there may be an inverse relationship between fluid intake and the incidence of bladder cancer, colorectal cancer, premalignant adenomatous polyps, and fatal coronary heart disease with as little as 5 8oz glasses of fluid per day, but specific EBM-valid studies have yet to be done
• the body's innate osmoregulation (via ADH) has been well proven to maintain adequate fluid balance; individuals at risk for overhydrating themselves--and subsequent hyponatremia, etc.,--tend to have other risk factors such as diabetes insipidus or exposure to the recreational drug ecstasy
• one feels thirst when plasma osmolality has increased by about 2%; dehydration is defined as a loss of >3% of one's body weight or an increase in plasma osmolality of at least 5% so the admonition that by the time you're thirsty, you're already dehydrated is not necessarily true

With this information in hand, it should be easier to relieve patients of their guilt about "not drinking enough water."