[Diabetes-talk] The Eight Glasses of Water Myth

[Mike Freeman]

I'm sure we've all read and heard the old saw that one must drink eight
glasses of water a day to stay healthy and this is doubly true for
diabetics. In fact, in a good book published by the American Diabetes
Association, Sex and Diabetes: For Him and For Her, this instruction was
given weight. We've also been told that drinking large quantities of coffee
or tea dehydrates us.

 

However, it ain't so. Normally, I just give links to Snopes stories but I
hear this one often enough that I'm pasting the entry, penned April 10,
below.

 

Happy reading.

 

Mike Freeman

 

 

 

 

snopes.com: Eight Glasses: Water vs. Coke

snopes.com

j

Medical

> 

Medical Myths

 

 

Water Works

Claim: The average person needs to drink eight glasses of water per day to
avoid being "chronically dehydrated." 

 

FALSE 

Example: [Collected via e-mail, 2001]

 

75% of Americans are chronically dehydrated. 

 

In 37% of Americans, the thirst mechanism is so weak that it is often
mistaken for hunger. 

 

Even mild dehydration will slow down one's metabolism as much as 30%. 

 

One glass of water shut down midnight hunger pangs for almost 100% of the
dieters studied in a U-Washington study. 

 

Lack of water is the number one trigger of daytime fatigue. 

 

Preliminary research indicates that 8-10 glasses of water a day could
significantly ease back and joint pain for up to 80% of sufferers. 

 

A mere 2% drop in body water can trigger fuzzy short-term memory, trouble
with basic math, and difficulty focusing on the computer screen or on a
printed

page. 

 

Drinking 5 glasses of water daily decreases the risk of colon cancer by 45%,
plus it can slash the risk of breast cancer by 79%, and one is 50% less
likely

to develop bladder cancer. 

 

Are you drinking a healthy amount of water each day? 

Variations: Some versions of this item are titled "Water vs. Coke" and tack
claims about the supposedly deleterious effects of Coca-Cola (which we have

covered in a separate 

article)

onto the end of this piece. 

 

Origins: "You need to drink eight glasses of water per day to be healthy" is
one of our more widely-known basic health tips.  But do we really need 

to drink that much water on a daily basis? 

 

In general, to remain healthy we need to take in enough water to replace the
amount we lose daily through excretion, perspiration, and other bodily
functions,

but that amount can vary widely from person to person, based upon a variety
of factors such as age, physical condition, activity level, and climate.
The

"8 glasses of water per day" is a rule of thumb, not an absolute minimum,
and not all of our water intake need come in the form of drinking water. 

 

The origins of the 8-10 glasses per day figure remain elusive.  As a Los
Angeles Times article on the subject reported: 

Consider that first commandment of good health: Drink at least eight 8-ounce
glasses of water a day. This unquestioned rule is itself a question mark.

Most nutritionists have no idea where it comes from. "I can't even tell you
that," says Barbara Rolls, a nutrition researcher at Pennsylvania State
University,

"and I've written a book on water." 

 

Some say the number was derived from fluid intake measurements taken decades
ago among hospital patients on IVs; others say it's less a measure of what

people need than a convenient reference point, especially for those who are
prone to dehydration, such as many elderly people. 

Back in 1945 the Food and Nutrition Board of the National Research Council
stated that adults should take in about 2.5 liters of water per day (which
is

roughly the equivalent of eight glasses of water), but it also noted most of
that intake level was already satisfied through the consumption of food
without

the need for the additional drinking of water.  And as other nutritionists
of the time noted, any shortfall in water intake could be made up through
the

consumption of beverages such as coffee, tea, milk, or soft drinks; one need
not specifically drink water only in the form of water. 

 

As Drs. Aaron E. Carroll and Rachel C. Vreeman reported in an article on
this topic: 

There's nothing wrong with liking water, but there is no scientific proof
stating that you need to drink anywhere near eight glasses a day.  One
doctor

who has made this his research focus, Dr. Heinz Valtin, searched through
many electronic databases and also consulted with nutritionists and
colleagues

who specialize in water balance in the body.  In all of his research, and in
all of the research we conducted to double-check his work, no scientific
evidence

could be found to suggest that you need to drink eight glasses of water a
day. In fact, scientific studies suggest that you already get enough liquid
from

what you're drinking and eating on a daily basis. We are not all walking
around in a state of dehydration. 

Other medical experts have also disdained the notion that one need drink at
least eight glasses of water per day to remain adequately hydrated: 

Kidney specialists do agree on one thing, however: that the 8-by-8 rule is a
gross overestimate of any required minimum. To replace daily losses of
water,

an average-sized adult with healthy kidneys sitting in a temperate climate
needs no more than one liter of fluid, according to Jurgen Schnermann, a
kidney

physiologist at the National Institutes of Health. 

 

One liter is the equivalent of about four 8-ounce glasses. According to most
estimates, that's roughly the amount of water most Americans get in solid

food.  In short, though doctors don't recommend it, many of us could cover
our bare-minimum daily water needs without drinking anything during the day.

 

Certainly there are beneficial health effects attendant with being
adequately hydrated, and some studies have seemingly demonstrated
correlations between

such variables as increased water intake and a decreased risk of colon
cancer. But are 75% of Americans really "chronically dehydrated," as claimed
in

the anonymous e-mail quoted in our example?  Many of the notions (and
dubious "facts") presented in that e-mail seem to have been taken from the
book 

Your Body's Many Cries for Water,

by Fereydoon Batmanghelidj. Dr. Batmanghelidj, an Iranian-born physician who
now lives in the U.S., maintains that people "need to learn they're not
sick,

only thirsty," and that simply drinking more water "cures many diseases like
arthritis, angina, migraines, hypertension and asthma." However, he arrived

at his conclusions through reading, not research, and he claims that his
ideas represent a "paradigm shift" that required him to self-publish his
book

lest his findings "be suppressed.'' 

 

Other doctors certainly take issue with his figures: 

[S]ome nutritionists insist that half the country is walking around
dehydrated. We drink too much coffee, tea and sodas containing caffeine,
which prompts

the body to lose water, they say; and when we are dehydrated, we don't know
enough to drink. 

 

Can it be so? Should healthy adults really be stalking the water cooler to
protect themselves from creeping dehydration? 

 

Not at all, doctors say. "The notion that there is widespread dehydration
has no basis in medical fact," says Dr. Robert Alpern, dean of the medical
school

at the University of Texas Southwestern Medical Center in Dallas. 

 

Doctors from a wide range of specialties agree: By all evidence, we are a
well-hydrated nation. Furthermore, they say, the current infatuation with
water

as an all-purpose health potion - tonic for the skin, key to weight loss -
is a blend of fashion and fiction and very little science. 

Additionally, the idea that one must specifically drink water because the
diuretic effects of caffeinated drinks such as coffee, tea, and soda
actually

produce a net loss of fluid is erroneous: 

Regular coffee and tea drinkers become accustomed to caffeine and lose
little, if any, fluid. In a study published in the October issue of the
Journal

of the American College of Nutrition, researchers at the Center for Human
Nutrition in Omaha measured how different combinations of water, coffee and
caffeinated

sodas affected the hydration status of 18 healthy adults who drink
caffeinated beverages routinely. 

 

"We found no significant differences at all," says nutritionist Ann
Grandjean, the study's lead author. "The purpose of the study was to find
out if caffeine

is dehydrating in healthy people who are drinking normal amounts of it. It
is not." 

 

The same goes for tea, juice, milk and caffeinated sodas: One glass provides
about the same amount of hydrating fluid as a glass of water. The only
common

drinks that produce a net loss of fluids are those containing alcohol - and
usually it takes more than one of those to cause noticeable dehydration,
doctors

say. 

The best general advice is to rely upon your normal senses.  If you feel
thirsty, drink; if you don't feel thirsty, don't drink unless you want to.
The

human body already does a good job of regulating water balance on its own,
and you therefore need not force yourself to drink when you are not thirsty

for fear of being dehydrated.  The exhortation that we all need to satisfy
an arbitrarily rigid rule about how much water we must drink every day was
aptly

skewered in a letter by a Los Angeles Times reader: 

Although not trained in medicine or nutrition, I intuitively knew that the
advice to drink eight glasses of water per day was nonsense. The advice
fully

meets three important criteria for being an American health urban legend:
excess, public virtue, and the search for a cheap "magic bullet." 

Last updated: 10 April 2013 

 

Urban Legends Reference Pages C 1995-2013 by Barbara and David P. Mikkelson.


 This material may not be reproduced without permission. 

 snopes and the snopes.com logo are registered service marks of snopes.com.

 

Sources:

definition list of 9 items

Batmanghelidj, Fereydoon. Your Body's Many Cries for Water.

Global Health Solutions, 1995.    ISBN 0-962-99423-5.

 

Carey, Benedict.   "Hard to Swallow."

Los Angeles Times. 20 November 2001   (Health; p. 1).

 

Carroll, Aaron E and Rachel C. Vreeman. Don't Swallow Your Gum!

New York: St. Martin's Griffin, 2009.   ISBN 0-312-53387-X   (pp. 130-133).

 

Foreman, Judy.   "The Water Fad Has People Soaking It Up." 

The Boston Globe. 11 May 1998   (p. C1).

 

Hoolihan, Charlie.    "Body Needs Plenty of Water to Work."

The [New Orleans] Times-Picayune. 31 May 1998.

 

CNN.com. "Americans Need to Shake Salt Habit."

11 February 2004.

 

Los Angeles Times. "All That Water Advice Just Doesn't Wash."

15 January 2001   (Health; p. 7).

 

Los Angeles Times. "Readers Take Issue with Article About Water
Consumption."

25 January 2000   (Health; p. 5).

 

The Toronto Star. "Distilling Water Facts from Water Fiction."

21 March 1999.

list end