There a lot of myths about the effects of salt consumption--both among
endurance athletes and in the general population.
Last
year my father-in-law and his wife visited my wife and me at our home
in California. My wife cooked up lots of good food for all of us. But
her dad has high blood pressure and is scrupulous in his avoidance of
salt. So he asked her to cook without it, and advised us to avoid
excess salt in our own diet
I
was tempted to disabuse the man of the widely held but false notion
that high levels of salt consumption cause hypertension, but I held my
tongue, because that’s what one does with one’s father-in-law. But I
certainly went right on eating a high-salt diet after he returned home.
The
research-supported truth is that salt avoidance is beneficial only for
the roughly 30 percent of already-hypertensive individuals who are
“salt sensitive.” In the rest of us, salt intake does not have a
significant effect on blood pressure. A recent review of 114 studies
performed by researchers from the University of Copenhagen and
published in the Journal of the American Medical Association found
that even an extreme reduction in salt intake would barely lower blood
pressure to a measurable degree in those with normal blood pressure.
Endurance
athletes have a more favorable view toward salt than the average person
does. That’s because we know that we lose a lot of salt every day
through exercise-induced sweating, and we’re used to consuming salt in
sports drinks during exercise to compensate for those losses. Failure
to do so, we’ve been taught, will cause internal fluid imbalances and
muscle cramps.
Or
are these notions false too? The answer is yes and no. There is
surprisingly little scientific evidence that salt consumption during
exercise provides any benefit. However, the practice does no harm and
is advisable whenever large volumes of sweat are lost and large volumes
of fluid are consumed during very prolonged exercise.
The
notion that sodium depletion during exercise causes muscle cramps is
clearly false. A 2005 study found no difference in blood sodium levels
between athletes who suffered muscle cramps and athletes who did not
during an Ironman triathlon. Some exercise physiologists now believe
that exercise-induced muscle cramps represent a type of tendon fatigue
that occurs during unaccustomed levels of exertion. The fact that some
athletes are especially prone to muscle cramps while others are not
also suggests that sodium depletion is not the cause.
However,
there is some evidence that consuming fluid and salt during prolonged
exercise may at least delay cramping in those who are susceptible. In a
study from the University of North Carolina, cramp-susceptible athletes
were able to exercise twice as long before experiencing cramps when
they consumed a sports drink during activity than they when they did
not drink.
Gatorade
teaches athletes that the addition of sodium to a sports drink improves
hydration by increasing the rate at which fluid is absorbed into the
blood stream and by slowing the decline in blood volume. But most
research supports neither of these claims. A study from the University
of Iowa found that sports drinks with different levels of osmolality,
both with and without salt, were all absorbed at the same rate during
exercise and none reduced blood volume decline more than
another. Studies from the University of Cape Town, South Africa, and
the University of Auckland, New Zealand, found that sodium
supplementation during an Ironman triathlon had no effect on blood
sodium concentration or blood plasma volume.
Interestingly,
the studies showing the greatest beneficial impact of salt on exercise
have involved sodium loading before exercise instead of sodium intake
during exercise. Another group of New Zealand researchers found that
when runners consumed a highly concentrated sodium beverage prior
running to exhaustion at 70 percent of VO2max in a hot environment,
they maintained a higher blood volume, lower core body temperature and
lower level of perceived exertion than when they consumed a low-sodium
beverage before running. It’s tough to know what to make of this
result, though, since no fluid was consumed during the runs.
No
study has found that consuming salt during endurance exercise has a
detrimental effect on performance. Couple that fact with the mountains
of anecdotal evidence from real athletes who say that salt intake is
beneficial to them in extreme endurance events such 100-mile runs and
you get the following sensible prescription: Consume salt in the normal
amounts contained in sports drinks and energy gels during prolonged
endurance exercise, but don’t knock yourself out to get more salt in
the form of salt tablets or salty foods.
Nor
do you need to add salt to your diet. However, you just might do it
unconsciously anyway. A 1999 Israeli study found that exercise
increased the preference for salty foods. So that’s why you crave potato chips after a long weekend endurance session!
Nutrition article courtesy of PacificHealth Laboratories, makers of nutrition tools such as Accelerade, Accel Gel, Endurox R4, Endurox Excel and much more. For product information or to purchase products, please visit www.pacifichealthlabs.com.
