On Hydration
There has been a long-standing argument about how
to
properly maintain adequate hydration. There are proponents of
everything from pure
water up through full-strength sports drinks with various additives.
While the Æther
echos with the debate and sports drink companies rake in the gold,
research has
continued since my last article on hydration 10 years ago, perhaps
shedding
more light on this arcane topic.
In order for the body to operate at peak
efficiency,
it needs to do four things: 1) maintain body temperature 2) maintain
hydration
3) maintain energy levels, and 4) maintain electrolytes (salts,
especially
sodium).
Peak exercise efficiency occurs at a body
temperature slightly above normal (thus the recommendation to warm up
prior to
exercise). To keep from overheating, the body produces sweat which
cools by
evaporation. The sweat contains water and salt, however the
concentration of
salt in sweat is much less than in the blood. Therefore, when you
sweat, you
lose more water than salt causing your blood to have increasing
concentrations
of salt. As you become more used to the heat, the sweat becomes even
more
dilute and you lose even more water in proportion to the salt loss.
This means
it is much more important to replace water than salt, at least in the
short
run. Most SCA combat activities don’t last long enough to
require additional
energy or salt supplements (such as carbohydrates [sugars]) during that
activity. Energy can be replenished by having a small snack between
bouts in a
list. During extended melees or wars there may be some benefit to
rehydrating
with a carbohydrate-containing drink.
What is the best way to replenish what the body
needs? At a minimum, you should be drinking water. Contrary to some
older
recommendations, research has shown that drinking when you are thirsty
is actually
a pretty good method of staying hydrated. In fact, one study that
carefully
looked at thirst and the concentration of salts in the blood concluded
that
people will become thirsty and drink before any decrease in body water
was
detected. The old mantra of "if you're thirsty, you're already
dehydrated" may not hold water (so to speak). Other studies show that
you
may be about 2% low before thirst kicks in, but that level of mild
dehydration won't
affect physical performance.
Daily water requirements range from 2 L (a bit over
2
quarts) in normal climates with low exercise to 15 L (4 gallons) with
heavy
exercise in the desert. Urine color is a good indicator of your
hydration
status. Urine that is no darker than weak lemonade indicates good
hydration (note
that certain foods, vitamins, and medications can color the urine
making
hydration hard to assess).
The salt losses are more than adequately replaced
by
eating a normal diet. The goal is to replace water loss
minute-by-minute and
salt losses day-by-day.
By now almost everyone is familiar with the problem
of drinking too much water (hyponatremia or water intoxication). This
is
actually very rare and is only seen in endurance races such as
ultramarathons
where the participant drinks excessive amounts of water over several
hours of
participation. It typically takes at least 5 hours of prolonged
exercise with
excessive drinking to get to the point of hyponatremia with most cases
occurring
with activity of more than 8 hours. Dehydration
is much more common to see in SCA activities. Don’t hold off
drinking water for
fear of this rare condition.
The ideas about effects of the carbohydrate (sugar)
content of sports drinks has changed over the years. Some studies from
the
1960s showed that carbohydrates in drinks slowed the rate that they are
absorbed from the stomach. This is the reasoning behind the
recommendation to
dilute sports drinks in half. More recent studies have shown this not
to be
true. However, drinks with more than about 10% carbohydrate content can
cause
cramps, nausea, and diarrhea. Not something you want to have in the
finals of
Crown Tourney, or, as one author put it, “You'll be running,
but not
necessarily on the field!" Products that are under 8% carbohydrate do
not
need to be diluted. Gatorade® at its
recommended strength is 6%
carbohydrate, and therefore does not need to be diluted. Diluting the
drinks
can make the mixes go farther and can make limited money and/or
supplies last
longer.
A misconception commonly encountered is that
drinking cold drinks causes stomach cramps and delays stomach emptying.
This
has not been borne out in experimental trials. In fact, cold liquids
stimulate
the emptying of the stomach. Cool drinks are probably still better
tolerated
than ice cold (ever get a ‘brain freeze’?)
If you use carbohydrate-containing drinks, be
careful that the containers are protected from insects. Bees and other
stinging
insects especially like sweet drinks. Rapidly swigging down a drink
that
contains a bee quenching his thirst can be very surprising for both the
bee and
the drinker, with disastrous results for both. Sports-top bottles are
great for
keeping the insects out and are easy to squirt through most helms. Soda
cans
are terrible as you can’t see what you’re drinking
– be it hornet or cigarette
butt! Make sure sweet liquids are properly stored and reusable
containers are
thoroughly cleaned as bacteria grow most heartily in sweet liquids.
Conventional wisdom has always been to avoid drinks
with caffeine because it increases urine output. The studies that this
conclusion is based on took people who had abstained from caffeine for
a period
of time. When they were subsequently given caffeine, they did have an
increase
in urine production. However, when a person has been imbibing caffeine
for
approximately four days, the effect on urine production goes away.
Drinks that
should be avoided are those that contain alcohol, carbonation, and
fruit
juices. Alcohol does cause increased urine production. Carbonated
drinks can
cause you to feel more full due to the bubbles in the stomach reducing
the
amount of fluid you’ll drink and possibly causing cramping
and discomfort
during exercise. Soft drinks are both carbonated and have high
carbohydrate
concentrations. Fruit juices are typically well above the recommended
10%
carbohydrate level. Salt tablets should not be used as they irritate
the
stomach and can potentially send a person’s salt levels too
high, which can
also be life-threatening. The American average diet contains adequate
salt to
replace losses and salting food to taste has been shown to adequately
replace
electrolytes.
Energy drinks are overall bad news with lots of
marketing hype and no proven performance enhancement. Some additives
can be
dangerous, if not deadly. Ephedra was removed from the US market
several years
ago due to its association with numerous deaths, some due to heat
stroke. Other
additives for improved energy (usually caffeine or its
“natural” cousin
guarana) may be high enough to stimulate urine production or cause
heart
problems. Creatine has been commonly used as a muscle-building and
recovery aid.
Unfortunately, it really doesn't increase the amount of muscle but
pulls water
into the muscle cells and out of the circulation. The muscles look
bigger, but
aren't any stronger. It has been associated with at least one
dehydration death.
Protein supplements put a load on the kidneys. Most people who eat meat
will plenty
of protein from their diet, even body builders.
Many
of the recommendations for increased fluid
intake during exercise has been driven by sports drink companies quest
for your
hard-earned money rather than good science. Don’t let the
hype get in the way
of taking proper care of yourself or your SCA brethren. Even a drink
that has
the proper balance of nutrients does no good if no one will drink it.
Pick a non-alcoholic,
non-carbonated, low-sugar drink that your local group likes and will
drink
plenty of and make sure it's easily available. Don't take the advice of
"The Most Interesting Man in the World" - Don't "Stay thirsty,
my friends".
References:
----. The Textbooks of Military
Medicine: Medical Aspects of Harsh Environments,
Vol. 1. The Borden
Institute.
2002.
Chapter 5.
Pathophysiology of Heatstroke
Chapter 6.
Prevention of Heat Illness
Armstrong, Lawrence E. Performing in Extreme Environments. Human Kinetics. 2000.
Bookspan, Jolie. Health & Fitness in Plain English, 3nd Edition. Healthy
Learning. 2008.
Montain, Scott J, and Matthew Ely. Water
Requirements and Soldier Hydration: Chapter 7 of Military Quantitative
Physiolgy: Problems and Concepts in Operational Medicine.
Borden Institute.
2012.
Tucker, Ross, and Jonathan
Dugas. Fluid Intake, Dehydration, and Exercise.
Accessed on 28 Aug 2015.
Copyright © 2015 Galen of Ockham, MC, OP (MKA Keith E. Brandt, M.D., M.P.H.) May be used in SCA publications as long as content is not modified and proper credit given. For all other uses, please contact the author at galen@chirurgeon.org .
Return to the Chirurgeons'
Point