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| The Dehydration Clock |
Have you ever been dehydrated? Probably, although you might not have
realized it at the time. You might even be
dehydrated right now and not know it. I was
severely dehydrated once; it was two summers ago on the Nipissing River, in
Algonquin Park. That morning it had
rained hard for several hours, then the sun had come out and it gotten hot. We were on the water for more than 10 hours
and had canoed close to 25 miles, with almost two miles of combined portages. We only had one quart of water each. It was too wet to light a fire to boil water
and the river water was so full of plant matter that it was the color of tea
and would have plugged our filters. By
the end of the day, I had a headache and it was hard to think; I was severely
dehydrated and it wasn’t much fun.
So, what is dehydration and how do you avoid it? Dehydration is when you lose more fluids than
you take in, and you just need to drink more, right? Well, yes and no, it is a little more
complicated than that, particularly if your water supply is limited.
All of the chemical activities in your body take place
in a water solution and water plays a vital role in maintaining your body’s temperature. Normal human body temperature is 98.6o F
and staying at this temperature is critical, an increase or decrease of just a
few degrees reduces your efficiency and puts you in danger of starting done a
slippery, and potentially fatal, slope by exceeding either the upper or the
lower limits of human temperature tolerance.
Your body constantly loses water through body processes, which remove
toxic body wastes, such as breathing, urinating and defecating. Other factors, such as heat exposure, cold
exposure, exercise, high altitude activity, burns, or illness, can also cause
your body to lose water. The body
temperature of an otherwise healthy person can be raised by absorbing too much
heat from the air, if the air is above 92oF, from direct sunlight or
radiant heat from the ground, from a sun-warmed object or a fire or by
generating body heat from exercise. However,
it doesn’t matter where the excess heat originally came from, your body must maintain
a normal temperature of 98.6o F and to do this the body must get rid
of excess heat, and it does this by sweating.
When you sweat, your body loses water, and you become
dehydrated. Since humans are mostly
water, about 60%, and since every drop in your body is needed, losses must be
made up. If the water loss is not made
up, the body becomes dehydrated and begins to operate with less efficiency. Dehydration,
of less than 2% of your body weight does you no harm and many people are regularly
this dehydrated; right now, while you read this article, you might be this dehydrated! Many people regularly lose between 2% to 5%
of their body weight without any long-term effect, by not drinking between
meals and then waiting to drink fluids at mealtime. At a loss 2.5% of body weight, which is about 2
quarts of body fluid, work efficiency decreases by 25 percent. When this happens, for example, you
will only be able to walk ¾ as far and as fast, work only ¾ as hard or lift just
¾ as much, as you could if fully hydrated.
At a loss 10% of your body weight, you will
experience a 30% to 40% decrease in your ability to regulate your body temperature. A loss of fluid equal to 15 percent of your body
weight is, unfortunately, usually fatal.
A
person’s daily water requirements depend on the environment, whether hot, cold,
temperate, humid or dry, their level of exercise and how long they exercise,
and their body size and gender.
When
most people think about when and where dehydration happens, they think about
the hot areas, however it is just as easy to become dehydrated in temperate,
cold or high altitude regions. The only
difference is that in hot areas you know when you are sweating and losing
precious body fluids. In cold regions,
because you are bundled up in many layers of clothes, sweating is not as obvious
as the clothes soak up and distribute the perspiration.
Cold environments are
less dehydrating than hot environments, since 75% of your body’s excess heat
can be dissipated into the environment without sweating, and the average person
in a cold environment requires from two to six quarts of water daily, depending
on their exercise level. In addition, any
physical activity in the snow requires more energy, and therefore generates
more waste heat, because of the heavier layers of clothes worn and the
additional effort required to move in the snow.
In
cold environments or temperate climates when it is cold, you must always limit
sweating: sweating not only dehydrates you, in these climates, it can also chill you
and that can kill you. To reduce the
amount you sweat, you should layer your clothes so that as you heat up you can
remove a layer and maintain a comfortably cold temperature. Since you head is your body’s radiator, put
on or take off, a knit cap as you warm up, or cool down. Also, whenever possible stay out of the wind,
not only will it cool you down, perhaps more than you would like, but just like
in hot and dry environments it will also dehydrate you.
In temperate climates,
depending on the season, you can release about 50% of your excess body heat
into the environment without sweating and on average, you will require from two
to five quarts of water daily.
Hot and dry or hot and
humid regions are the most dehydrating of all environments, as you are unable
to dissipate excess body heat without sweating, and you will need an average of
three to ten quarts of water each day: the harder or longer you work, the more
water you will need. In
these climates, limit sweat-producing activities or do required tasks when it
is cooler, before 9:00 am and after 3:00 pm.
Wear light-colored clothing because it reflects sunlight and heat, while
dark-colored clothing absorbs heat, and keep your body covered, as this
prevents sunburn, and in hot and dry conditions if you wear light, loose
fitting, breathable clothes you will sweat less than if you were few or next to
no clothes. Loose fitting clothes
efficiently use your sweat to keep you cool and your bare skin or your bare
head when exposed to the sun and wind requires significantly more sweat to keep
cool, as it evaporates quickly off your skin.
Also, since your head’s is your body’s radiator, keep it covered with a
wide brimmed hat, to keep your whole body cool.
Stay in the shade and out of the wind during the hottest part of the
day, since, the sun warms you and the wind will dry you and both cause you to
dehydrate. In a survival situation, find
or build a shelter to block the sun and wind.
Also, avoid sitting or lying on the ground if it has been in the direct
sun; sit a few inches off the ground, since the air is 30oF to 45oF
cooler 12” above the ground. If you must
sit or lay down on the ground, dig down below the ground surface at least 3”,
as the subsurface dirt will be up to 30oF cooler. It is important to remember that if your
water is limited, KEEP YOUR MOUTH CLOSED and if possible BREATHE THROUGH YOUR
NOSE, because breathing through your mouth dries your mouth, tongue and mucous
membranes and increases the rate of dehydration, similarly, do not talk or
smoke as they encourage breathing through your mouth. Additionally, if your water is limited do not
eat, as food or alcohol require additional water to digest and will further
dehydrate you.
In high altitude
environments, because every activity takes more energy due to the altitude and the
bulky clothing worn, and because the air is drier, you will need between four
and five quarts of water each day.
Your
activity level will dramatically change the amount of fluids that you require
each day. For example, in a temperate
climate when at rest, the average adult weighing 154 pounds will need approximately 3
quarts of water each day; this same adult requires a minimum of
approximately 1½ quarts of water each day just for normal body processes. An
average adult doing moderate work, such as hiking over rough ground for several
hours, will need approximately four to six quarts of water each day. This same average adult performing very heavy
work and hiking over rough ground, while carrying a heavy load for several
hours, will need from about six to fifteen quarts of water per day.
Your body size and
gender also play an important part in determining your daily water
requirements, since in general the larger you are the more energy is required
for any activity and the more waste heat you will generate. On average men are larger and heavier than
women and therefore will need more water each day.
Now that I have convinced you to drink a lot of water,
remember not to drink too much. You
shouldn’t drink more than 1½ quarts per hour or 12 quarts per day, or you might
suffer from hyponatremia or water intoxication; however, that is something for
another article.
Below
are some considerations for keeping hydrated while in the outdoors.
- Eat
regular meals, make time to drink, drink frequently, make sure the water tastes
good and is the right temperature.
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| FM 90-3 Desert Operations, p. 1-22 |
- Drink
before you become thirsty and drink often, thirst lags behind actual water
needs, so drink before you become thirsty.
When you become thirsty, you are already about a "quart low". Since the sensation of thirst is not felt until the body has already
lost 1% of its total body fluids or about ¾ of a quart of water, drink even if you are not thirsty right now.
- Being
thirsty makes it harder to stay warm, and in hot climates hard to stay cool.
- Take
frequent drinks since it is better to drink smaller quantities of water often,
rather than large quantities occasionally, because drinking small quantities of
water frequently results in less urination than drinking large quantities infrequently. You should drink a small quantity of water
every 50 minutes.
- Drink
one quart of water in the morning, since you are dehydrated when you wake up,
one quart at each meal, and one quart before strenuous work. In hot climates,
drink at least one quart of water each hour.
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| FM 90-3 Desert Operations, p. 1-24 |
- In
both hot and temperate conditions, cool drinks (50o-70oF)
increase your desire to drink fluids, cool you and are absorbed by your body faster
than cold water. In hot conditions when
water is warmer than 75o-80oF, people will not want to
drink it, make sure water is kept as cool as possible so it will be as drinkable
as possible.
- When
temperatures are cold, warm or hot drinks are preferable as they increase your desire
to drink fluids and warm the body. The
popular view is that tea or coffee are dehydrating and that you should not be
drink them to replenish your body fluids.
While caffeine is a very mild diuretic, the caution to stay away from
them has been exaggerated and the caffeine in caffeinated drinks leads to a
loss of less water than the water that is in the beverage itself. Caffeine is only a problem if your entire
fluid intake comes from caffeinated drinks.
Current research shows that drinking up to four mugs of black tea is as
effective as a similar quantity of water, at rehydrating your body Hot cocoa might be better choice in cold
climates than coffee, because it has less caffeine and has needed carbohydrates.
- How
a drink tastes is a major factor in how much is drank. Adding packets of artificial fruit flavoring or
sweeteners to your water can cover existing bad flavors in the water and encourage
you to drink more due to the pleasant taste.
- Gatorade
or other carbohydrate/electrolyte beverages are generally not required and if
used, should not be the only source of water; they are too concentrated to be
used alone. Many athletes prefer to dilute these 1:1 with water.
- Carbonated
drinks, sodas, beer, and milk are not good substitutes for water because they
are more food than drink and are dehydrating.
- Salt
is lost when you sweat; however eating your meals regularly and salting your
food to taste, usually provides enough salt to counter salt depletion from
sweating. If you are unable to eat
regularly, add a small quantity of salt (¾ of a teaspoon per quart or a pinch
into a mug) to your water, take a salt tablet or drink a sports drink like
Gatorade. If you are deficient in salt,
you will notice the following symptoms: weakness, muscle cramps, nausea and a
hot dry feeling over your entire body.
- If
your urine is dark yellow or orange and is less than normal, the last urination
cannot be remembered, or if skin has decreased turgor, you are probably
dehydrated.
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| Are You Hydrated Take the Urine Color Test (see sources) |
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| Turgor (see sources) |
- Water
is best carried in your belly, do not "save" it in your canteen, SO
DRINK your water as you need it, don’t ration your water.
- The
only way to conserve your drinking water is to ration your sweat, and not the
water in your canteen, so drink your water, as you need it. Water is best carried in your belly, do not
"save" it in your canteen, SO DRINK your water as you need it, don’t
ration your water.
- No
matter the environment that you are in, conserve your sweat not your water, simply
put “DON’T WORK UP A SWEAT”!
- Sucking
on a pebble or chewing gum masks the symptom of thirst and does you no
harm. However, it does not replenish
lost water and is not a substitute for drinking fluids.
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| The Dangers of Dehydration (see sources) |
Sources:
FM 90-3 Desert Operations, (Headquarters,
Department of the Army, US Marine Corps, Washington DC [1993])
FM 21-18 Foot Marches, (Headquarters,
Department of the Army, US Marine Corps, Washington DC [1990])
Paul H. Nesbitt, Ph.D., Alonzo W. Pond, and William H.
Allen, A Pilot’s Survival Manual, (A Van Nostrand Reinhold Company, New
York, NY [1978]) p. 201-207
