Many of us grew up reciting the directive, “Everyone should drink 8 glasses of water a day” – based on the glass holding 8 ounces. This advice was not research-based, and has been abandoned as a reliable guideline.
Water is undeniably important for our body to function
properly. Consider this educational diagram as developed by the Mayo Clinic:
I’ve often heard that most Americans are chronically
under-hydrated. I have no evidence to prove nor refute that statement. However,
I know many people who suffer from constipation, kidney stones, aching joints,
and are constantly too hot or too cold. Anecdotal at best, but just saying.
In the gym, I’m a big believer in staying hydrated. When
exercising, you are losing water through perspiration, evaporation, and
respiration. As the body heats up from exercise, a person sweats, the air,
which is drier, helps cool the skin through removing water molecules, and as
the exerciser is breathing harder, water content is carried with each exhale.
It’s estimated that our bodies are comprised of somewhere
around 66% fluid. Some people naturally sweat a lot, others don’t. Some bodies
are much bigger than others. Some people exercise hard, others do not. So, the
idea that everyone needs the same amount (eight 8-ounce glasses), does not hold
water (excuse the pun).
Too much water can lead to a dangerous condition known as
hyponatremia. When excessive amounts of water are added to the “system,” the
ratio of sodium to water lowers – dilution. If the body doesn’t have added
“space” or “time” to bring about a balance (homeostasis), the excess water can
cause swelling of tissues due to cells absorbing more water than normal. If
this happens to the brain tissue, and the brain swells – it has nowhere to go
other than up against the skull. This could lead to seizure, coma,
respiratory arrest, and/or death. Overdosing on water, water intoxication, is
rare – usually observed when someone participates in a prank or contest to
observe, “who can drink the most water.”[1]
So, not enough and your bodily systems cannot function
optimally, and way too much can lead to water intoxication. What’s the right
amount? Current research says to let your thirst guide you. (A
cautionary note: I’ve observed many people who don’t pay attention to their
thirst and end up dehydrated because they ignored the signals. Additionally, it
has been widely noted that elderly people, in general, often ignore the need to
take in adequate fluid for a variety of reasons – one of these being incontinence.)
The Institute of Medicine’s 2004 guidelines (not requirements!) indicate that
on average, women need approximately 91 ounces (11+ cups) of fluid intake, while on average, men need
about 125 ounces (15+ cups) daily.[2] Fluid has been italicized as these
numbers take into consideration fluid from all food and beverages – not just
water. If a person’s diet includes
appropriate servings of fruits and vegetables, food has been generalized as
having 20% fluid we consume on a daily basis, while the remaining 80% comes
from water and other beverages.
Webmd states, “… the recommended amount of beverages,
including water, would be approximately 9 cups for women and 12.5 cups for
men.”Interestingly, I found a link (offered below) to a Water Intake Calculator,
that based on my weight, calculated my water needs as 12.75 cups/day.[3]
Calculator Pro Water Calculator (The inclusion of this calculator is not an endorsement of its accuracy; it's merely included as a tool, which seems somewhat consistent with the research cited.)
[1] Ballantyne,
C. (2007, June 23). Strange but True: Drinking Too Much Water Can Kill.
Retrieved April 21, 2015, from
http://www.scientificamerican.com/article/strange-but-true-drinking-too-much-water-can-kill/
[2] Dietary
Reference Intakes: Water, Potassium, Sodium, Chloride, and Sulfate - Institute
of Medicine. (n.d.). Retrieved April 21, 2015, from
http://www.iom.edu/Reports/2004/Dietary-Reference-Intakes-Water-Potassium-Sodium-Chloride-and-Sulfate.aspx
[3] Zelman,
K. (2005, April 1). Water: How Much to Drink, Water Content of Foods, Too Much
Water, and More. Retrieved April 21, 2015, from
http://www.webmd.com/a-to-z-guides/features/wonders-of-water?page=2&print=true
