Salt the only mineral you need to replace during exercise
Salt: the Only Mineral you Need to Replace During
Exercise

October 12, 2014
 by Gabe Mirkin, MD

The only mineral that you need to replace during
exercise lasting longer than three hours is
sodium, found in common table salt. You do not
need to take extra potassium, magnesium or any
other mineral during exercise.
 
The definitive studies on minerals and exercise
were done during World War II. Dr. James Gamble of
Harvard Medical School paid medical students to
lie on a raft in his swimming pool, take various
amounts of fluids and salt and have blood drawn to
measure salt and other mineral levels. He showed
that you have to take a lot of salt when you
exercise for several hours, particularly in hot
weather. For many years after that, every student
at Harvard Medical School heard Dr. Gamble give
his lectures on minerals and exercise, and today,
most serious medical students still read the
Gamble lectures published in 1958, since nobody
has improved on his research.
 
Salt but Not Salt Tablets
 After Dr. Gamble published his studies, people
who worked or exercised in the heat were given
salt tablets. Then doctors became concerned
because they thought that a person could have his
blood pressure raised by taking in too much salt.
Some people would vomit from the high
concentration of salt from salt pills in their
stomachs. However, salt restriction can cause
people to suffer heat stroke and dehydration
during hot weather exercise. A low-salt diet does
not lower high blood pressure for most people. A
high-salt diet causes high blood pressure usually
only in people with high blood insulin levels:
those with protruding bellies, overweight, and
high blood sugar levels. Eating salty foods and
drinks when you exercise for more than three hours
is unlikely to raise blood pressure. Doctors do
not recommend salt tablets today because they can
burn holes in your stomach and cause nausea and
vomiting.
 
Why You Need Extra Salt During Prolonged Exercise
in Hot Weather
 If you don’t take salt and fluids during extended
exercise in hot weather, you will tire earlier and
increase your risk for heat stroke, dehydration
and cramps. The rule is that people who are going
to exercise vigorously for more than three hours
continuously should take some source of salt while
they are exercising. Salty drinks taste awful, so
it is easier to meet your needs with salted foods.
If you plan to exercise for more than a couple
hours in hot weather, drink one or two cups of the
liquid of your choice each hour and eat a salty
food such as salted peanuts, potato chips or any
other salty food.
 
You Need Salt to Feel Thirsty
 Not taking in enough salt when you exercise for
more than three hours in hot weather can prevent
you from retaining the water that you drink. It
can also block thirst, so you may not know that
you are dehydrated. Thirst is a late sign of
dehydration. You lose water during exercise
primarily through sweating, and sweat contains a
far lower concentration of salt than blood. So
during exercise, you lose far more water than
salt, causing the concentration of salt in the
blood to rise. You will not feel thirsty until the
concentration of salt in the blood rises high
enough to trip off thirst osmoreceptors in your
brain, and it takes a loss of two to four pints of
fluid to do that (American Journal of Emergency
Medicine, 1999;17(6):532-539).
 
You Need Salt to Retain the Fluid You Drink While
Exercising
 In one study, female competitive distance runners
took in drinks with different concentrations of
salt during a four-hour run (British Journal of
Sports Medicine, August 2003). Ninety-two percent
of those who took in plain water with no
additional salt developed low blood levels of
salt.
 
Taking in fluid without also taking in adequate
amounts of salt dilutes the bloodstream so that
the concentration of salt in the blood is lower
than that in brain cells. This causes fluid to
move from the low-salt blood into the high-salt
brain, causing the brain to swell, which can cause
seizures and death. This is called hyponatremia,
the low salt syndrome that can kill. It is usually
caused by taking in far too much fluid, rather
than from not taking in enough salt.
 
How Salt Can Improve Performance in Competition
 Taking extra salt just prior to competition can
help you exercise longer and harder (Medicine and
Science in Sports and Exercise, January, 2007; and
Clinical Journal of Sport Medicine, January 2007).
Fatigue during hot-weather exercise is caused by
lack of water, salt, sugar or calories. Of the
four, exercisers are most ignorant of their salt
needs.
 
Always replace fluids, salt, sugar, and protein
after you exercise in hot weather. Just salting
your food to taste should replace the salt you
lose through heavy sweating. If your kidneys are
normal, you should be able to rid yourself of any
excess salt that you may take in.
 
How to Tell If You Need More Salt
 Salt deficiency causes tiredness, lethargy and
cramps. It also weakens muscles, causing you to
slow down and lose strength. If you suffer any of
these symptoms, you can get a blood test for
sodium and chloride on the day after a hard
workout. Low blood levels of sodium are most
likely to occur on the morning after you have
replaced fluid lost from heavy exercise. If your
blood sodium level is below 135, you are deficient
and need to add more salt to your food.
 
Who Is Most Likely to Suffer from Salt Deficiency?
 Vegetarians and people who limit meat are at
increased risk for salt deficiency because plants
are naturally low in salt. Meat, fish and chicken
naturally contain far more salt. Most processed
foods are high in salt because manufacturers know
that salt makes food taste good and is also a
preservative.
 
The North American diet typically contains up to
ten times the minimal daily salt requirement. If
you doubled or tripled your salt losses through
sweating, you may still not be deficient because
you probably take in far more salt than you need.
 
Does Extra Salt Cause High Blood Pressure and
Heart Attacks?
 A review of the world’s literature shows that
salt restriction does not lower high blood
pressure for most people with high blood pressure
(Journal of Hypertension. May 2011;29(5):821-828).
Eating salty foods and drinks when you exercise
for more than three hours is unlikely to raise
blood pressure. I found only six long-term follow
-up studies of salt intake and heart attacks.
Three of the studies suggest that very low salt
intake may cause heart attacks.
 
Exercise Can Prevent a Rise in Blood Pressure with
Extra Salt Intake
 Excessive intake of salt causes high blood
pressure in some, but not all, people. High blood
pressure increases risk for heart attacks,
strokes, and kidney damage. Many middle-aged
people who start an exercise program lose their
tendency to develop high blood pressure when they
take in extra salt (Journal of Human Hypertension,
May 2006). This study shows that many people who
develop high blood pressure from a high-salt diet
when they are sedentary, will not develop high
blood pressure on the same diet when they
exercise.
 
Metabolic Syndrome
 People with high blood sugar levels are the ones
who are most likely to develop high blood pressure
from excess salt intake. A high-salt diet causes
high blood pressure most commonly in people who
suffer from metabolic syndrome and are pre-
diabetic or diabetic (Lancet, March 2, 2009).
Metabolic syndrome occurs when cells lose their
ability to respond adequately to insulin and blood
levels of sugar rise too high. It is caused by:
 * eating too much sugar and other refined
carbohydrates,
 * being overweight,
 * not exercising, and
 * lacking vitamin D.
 Metabolic syndrome is characterized by storing
fat primarily in the belly, having a thick neck,
high blood triglycerides, low blood good HDL
cholesterol, high blood sugar, and eventually
liver damage and all the side effects of diabetes.
People with metabolic syndrome have a greater rise
in blood pressure with increased salt intake and a
drop in blood pressure with salt restriction.
 
Check Your Own Blood Pressure
 If you are concerned about your blood pressure,
you can buy an inexpensive wrist cuff and check
your systolic blood pressure at bedtime. If it is
below 120, you probably do not need to worry about
salt. If it is above 120, and particularly if you
store fat primarily in your belly rather than your
hips, your good HDL cholesterol is below 40, your
triglycerides are above 150, or you have a blood
sugar above 100 two hours after a meal or an HBA1C
above 5.9, you probably should restrict salt and
definitely should work to correct the causes of
metabolic syndrome:
 * lack of exercise,
 * overweight,
 * eating too much red meat,
 * taking sugared drinks and foods,
 * lack of vitamin D, and
 * not eating enough fruits and vegetables.
 
My Recommendations:
 If you do not exercise, you do not sweat very
much and you do not need very much salt. Too much
salt can increase blood volume which may raise
systolic blood pressure. Being fat is the primary
cause of elevated diastolic blood pressure. On the
other hand, if you exercise vigorously, you sweat
tremendously and lose a lot of salt. Without extra
salt during prolonged, vigorous exercise, you will
not perform at your best, you will not recover
from your hard bouts of exercise and you will be
more likely to be injured or tired all the time.