There has never been any supporting evidence to back up the popular recommendation to drink 8 glasses of water per day.
In an editorial for the June issue of Australian and New Zealand Journal of Public Health, Dr.
Spero Tsindos from La Trobe University says most people get enough
water from the foods and beverages — including tea and coffee.
Humans
need about two litres of fluids per day — not two litres of water
specifically. He even takes his message a step further by suggesting the
eight-glass-a-day rule is a myth invented by plastic water bottle
companies who have made it fashionable to tote around what he says have
become ubiquitous accessories.
“Health and dietary authorities currently encourage Australians to
consume eight glasses, or two litres, of fluid daily for optimal
health,” writes Tsindos.“This has been misinterpreted to mean two litres of water specifically
and it has driven a steady growth in the use of bottled water over the
years.”
Tsindos believes that encouraging people to drink more water is driven
by vested interests, rather than a need for better health.
“Thirty years
ago you didn’t see a plastic water bottle anywhere, now they appear as
fashion accessories.”“Research has also revealed that water in food eaten has a greater
benefit in weight reduction than avoiding foods altogether.We should be
telling people that beverages like tea and coffee contribute to a
person’s fluid needs and despite their caffeine content, do not lead to
dehydration.”“We need to maintain fluid balance and should drink water, but also
consider fluid in unprocessed fruits and vegetables and juices.”
In an previous review published by the American Journal of Physiology,
Heinz Valtin, a Dartmouth Medical School physician reported that there
is no supporting evidence to back up the popular recommendation to drink
eight 8 oz. glasses of water per day.
How did the 8 X 8 myth start? Valtin thinks that the notion may have
started in 1945 when the Food and Nutrition Board of the National
Research Council recommended approximately “1 milliliter of water for
each calorie of food,” which would amount to roughly 2 to 2.5 quarts per
day (64 to 80 ounces).
In its next sentence the board stated, “[M]ost of this quantity is contained in prepared foods.”
But that last sentence seems to have been missed, so that the
recommendation was erroneously interpreted as how much water a person
should drink each day.
Frederick J. Stare a renowned nutritionist, was a strong supporter of
the need to drink at least six glasses of water a day. Nevertheless, he
did not support water consumption on spurious scientific foundation.
In
his criticism of The Stillman Diet, he noted that Dr Stillman claimed
consuming eight glasses of water a day was necessary for the kidneys to
wash away the fatty acids resulting from the breakdown of fats. The
reasoning for this, Dr Stillman admitted, was not fully understood.
Suzanne Douglas, a Los Angeles based Nutritionist says that the 8
glasses of water myth was propagated by the chemical industry an entire
decade before the actual mass consumption of bottled water began.
“In
the 70s and 80s, the myth was promoted by several nutritionists with
direct ties to the chemical industry and by the late 80s plastic bottled
water began selling worldwide.”
The Mayo Clinic looks at both sides of the issue in an article titled, Water: How much should you drink every day?
And while they agree people do get a lot of water from certain foods
and beverages,
“these should not be a major portion of your daily total
fluid intake. Water is still your best bet because it’s calorie-free,
inexpensive and readily available.”
Their advice? Listen to your body and drink water accordingly. People
who are more active, live in warmer climates, are suffering from an
illness or who are pregnant or nursing may need to consume more water,
because they are losing more fluids from their bodies than others. As
long as you’re producing 1.5 litres of light yellow urine a day, you’re
good to go.
Douglas says that water content in foods is an essential part of our
dietary intake and should be included in the total amount of fluid we
are required to consume.
Water Content of Foods (In Water Percentage)
Apples: 85
Apricots: 85
Bean sprouts: 92
Chicken, boiled: 71
Cucumbers, raw: 96
Eggplant, raw: 92
Grapes: 82
Lettuce, head: 96
Oranges: 86
Peaches, raw: 90
Peppers, green: 94
Potatoes, raw: 85
Strawberries, raw: 90
Turkey, roasted: 62
Watermelon: 93
Caffeinated beverages and other drinks also should be counted toward
daily water intake. University of Nebraska researcher Ann Grandjean and
colleagues (Grandjean, 2000) conducted a study, published in the Journal of the American College of Nutrition,
about the effects of caffeinated beverages on hydration. Grandjean and
her colleagues used 18 healthy male adults for their subjects.
On four separate occasions, the subjects consumed water or water plus
varying combinations of beverages. The beverages were carbonated,
caffeinated, caloric, and noncaloric colas and coffee. Body weight,
urine, and blood evaluations were performed before and after each
treatment.
Grandjean found that there were no changes in the body weight, urine, or
blood evaluations for the different beverages.
The study found no
significant differences in the effect of various combinations of
beverages on the hydration status of healthy adult males.
Grandjean
concluded that advising people to disregard caffeinated beverages as
part of their daily fluid intake is not supported by the results of her
study.
She went on to say,
“[T]he purpose of the study was to find out if
caffeine was dehydrating in healthy people who are drinking normal
amounts. It is not.”
There seems to be a large number of people who
hold onto the myth that caffeine causes dehydration, probably because
that’s what they have always heard.
Under some circumstances, significant fluid intake — at least eight
8-ounce glasses — is advisable: for the treatment or prevention of
kidney stones, for example, as well as under special circumstances, such
as performing strenuous physical activity or enduring hot weather.
The global bottled water sales have increased dramatically over the past
several decades, reaching a valuation of around $60 billion and a
volume of more than 115,000,000 cubic metres (3.0×1010 US gal) in 2006.
U.S. sales reached around 30 billion bottles of water in 2008, a slight
drop from 2007 levels.
The global rate of consumption more than quadrupled between 1990 and
2005. Spring water and purified tap water are currently the leading
global sellers. By one estimate, approximately 50 billion bottles of
water are consumed per annum in the U.S. and around 200 billion bottles
globally.
According to Douglas the chemical and plastic industry has benefited by
the same proportions and valuation. “The exponential growth and profits
generated by global water sales are parallel to the growth experienced
by the chemical and plastic industry from 1990 to 2005,” she added.
Glasgow-based GP Margaret McCartney says the NHS Choices website’s
advice that people should drink six to eight glasses a day is ‘not only
nonsense, but thoroughly debunked nonsense’. She adds that the benefits
of the drink are often exaggerated by ‘organisations with vested
interests’ such as bottled water brands.
Writing in the British Medical Journal, Dr McCartney also points out
that research shows drinking when not thirsty can impair concentration,
rather than boost it, and separate evidence suggests that chemicals used
for disinfection found in bottled water could be bad for your health.
Drinking excessive amounts can also lead to loss of sleep as people have
to get up in the night to go to the toilet, and other studies show it
can even cause kidney damage, instead of preventing it.
The bottom line? Drink when you are thirsty, not because you believe you need to.
April McCarthy – June 10, 2012 – SignsOfTheTimes
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