There are very few areas of
nutrition that have garnered as much perplexity as the king of
all nutrients, and the world’s most prominent substance.
Okay, so we all know that water is good for us and that we should
drink plenty of it. Exactly how much water we need, however has
been the subject of much debate, and remains an enigma to this
day. Many medical and nutrition experts are dispelling the 8 -
8Oz. glasses a day gospel – an unsubstantiated idea that
has manifested itself into a commonly accepted belief. The origins
of the 8 glasses a day recommendation can be traced to Dr. Frederick
Stare; a Nutritionist who purported this theory in a book published
in 1974. This was simply a best guess on his part, however, as
he provided no scientific studies to support his assertion. One
could argue that the lucrative bottled water industry is largely
responsible for keeping the proverbial 8-a-day flame burning.
Water Intake – Not Just
As it turns out, it is possible
that Dr. Stare’s recommendations were simply misinterpreted.
Many studies have shown we actually do need at least 8 glasses
of water a day. But here’s the catch…that requisite
intake is satisfied not only from drinking water, but also from
other fluids we consume, the food we eat and the metabolic processes
required to break down that food. Juice and milk contribute to
hydration and (surprisingly enough) so do caffeinated and alcoholic
beverages (caution: moderation is recommended here). Many people
still believe that caffeine causes dehydration, even though studies
as early as 1928 have shown otherwise . The fluid from food and
its accompanying metabolic action alone can account for as much
as 6 glasses of water! Water is the best fluid – no argument
there. But don’t get caught up in the idiocy of forcing
down extra glasses of water if you have a coffee, or if you have
been drinking other fluids.
Water – is there such
thing as too much?
Like other aspects of health,
water is not immune to the “more-must-be-better” mentality
that many of us erroneously adopt. Although fatalities due to
over-hydration are rare, complications caused by drinking too
much water are markedly increasing. To illustrate, 31 runners
in the 2000 Houston Marathon were treated for hyponatremia - a
condition that can arise with excess fluid consumption, causing
a dilution of sodium in the blood. These cases have prompted medical
experts to shift away from the previous recommendations of “drinking
as much fluid as you can tolerate”, to “drink as needed,
but do not exceed 800ml per hour” . This is a potentially
important message for serious endurance athletes, who have never
given their copious water consumption a second thought.
Other water fallacies
Many of us have heard that
thirst is not a good predictor of hydration because by the time
we are thirsty, we are dehydrated. This popular contention has
been dismissed by many researchers as being generally false –
here’s why. The medically accepted definition of dehydration
is when a person has lost more than 3% of his/her body weight.
Meanwhile, in most cases, our thirst sensation kicks in when less
than 2% of body weight is lost . Therefore, under normal circumstances
most people can sustain adequate hydration using thirst as an
indicator. Another pervasive water myth is the “dark urine
= dehydration” theory. Although dark urine may indicate
dehydration, there are a multitude of other factors that can contribute
to this, and thus it is not an accurate gauge. And yet another
popular myth is that water keeps kidney filtration rate at optimal
levels. Unless there is an accompanying medical condition, kidney
filtration rate only suffers in cases of severe dehydration. We
could also use this opportunity to address bottled vs. tap vs.
distilled water, but for the sake of brevity – we’ll
leave that one alone!
Estimating water needs
• There is a large variation
when it comes to individual water needs. Those who are active
have increased water requirements, especially if exercising in
• As a baseline, 1L of water a day (about 3 glasses) should
be fine for those individuals who are relatively sedentary.
• Increasing water intake to 1.5-2.5L/day (4-5 glasses)
per day is a good idea if you are moderately to highly active,
and drink a few gulps every 15-30 minutes if exercising in hot
• If you are exercising for longer periods of time (going
on a long hike, as an example), be sure to consume some salt when
consuming large quantities of water.
• If fat loss is your goal, make water your primary beverage
– aim for 75% of your fluid consumption, while cutting back
on juice, pop and other calorie-containing liquids.
Water – The take-home message
There is no denying that drinking
water is vital to our health. It is the hub of all chemical reactions
in the body, and is the backbone of any sensible eating plan.
Further, the average person probably should be drinking more of
the stuff. Having said that, 8 glasses a day will keep most healthy
people running to the bathroom all day. Drink water whenever you
can – try to have a glass with each meal, and consume it
while you are exercising. Use common sense when hydrating during
exercising – especially in hot weather. You need not, however
count empty bottles, or stress if you were a glass short of what
a select few deem “required”.
1 Stare, FJ, and
McWilliams M. Nutrition for Good Health. Fullerton, CA: Plycon,
1974, p. 175
2 Grandjean, AC, Reimers KJ, Bannick KE, and Haven MC. The effect
of caffeinated, non-caffeinated, caloric and non-caloric beverages
on hydration. J Am Coll Nutr 19: 591-600, 2000.
3 Tufts University Health and Nutrition Letter. New Consumption
Guidelines for Water Sodium, Potassium. April, 2004
4 THE PHYSICIAN AND SPORTSMEDICINE - VOL 31 - NO. 7 - JULY 2003.
New Hydration Recommendations.
5 Casa DJ: Proper hydration for distance running: identifying
individual fluid needs. Available at http://www.usatf.org.
6 Weinberg, A, and Minaker K. Council of Scientific Affairs, American
Medical Association: dehydration evaluation and management in
older adults. JAMA 274: 1552-1556, 1995
Mike Howard is
the owner of Core Concepts Wellness Solutions – a health
and fitness services provider that specializes in health seminars,
personal training and workplace wellness. He is the author of
“Winning the Losing Battle - The Truth about Fat Loss©”,
and teaches courses based on the manual in the Greater Vancouver
area. For more information, he can be reached at firstname.lastname@example.org