Role of Potassium in Maintaining Health
Potassium is a very significant body mineral,
important to both cellular and electrical function. It is one of the main blood
minerals called "electrolytes" (the others are sodium and chloride),
which means it carries a tiny electrical charge (potential). Potassium is the
primary positive ion (cation) found within the cells, where 98 percent of the
120 grams of potassium contained in the body is found. The blood serum contains
about 4-5 mg. (per 100 ml.) of the total potassium; the red blood cells contain
420 mg., which is why a red-blood-cell level is a better indication of an
individual's potassium status than the commonly used serum level.
Magnesium helps maintain the potassium in the
cells, but the sodium and potassium balance is as finely tuned as those of
calcium and phosphorus or calcium and magnesium. Research has found that a
high-sodium diet with low potassium intake influences vascular volume and tends
to elevate the blood pressure. Then doctors may prescribe diuretics that can
cause even more potassium loss, aggravating the underlying problems. The
appropriate course is to shift to natural, potassium foods and away from
high-salt foods, lose weight if needed, and follow an exercise program to
improve cardiovascular tone and physical stamina.
The natural diet high in fruits, vegetables, and
whole grains is rich in potassium and low in sodium, helping to maintain normal
blood pressure and sometimes lowering elevated blood pressure. The body
contains more potassium than sodium, about nine ounces to four, but the
American diet, with its reliance on fast foods, packaged convenience foods,
chips, and salt has become high in sodium (salt). Because the body's biochemical
functions are based on the components found in a natural diet, special
mechanisms conserve sodium, while potassium is conserved somewhat less.
Potassium is well absorbed from the small
intestine, with about 90 percent absorption, but is one of the most soluble
minerals, so it is easily lost in cooking and processing foods. Most excess
potassium is eliminated in the urine; some is eliminated in the sweat. When we
perspire a great deal, we should replace our fluids with orange juice or
vegetable juice containing potassium rather than just taking salt tablets. The
kidneys are the chief regulators of our body potassium, keeping the blood
levels steady even with wide variation in intake. The adrenal hormone
aldosterone stimulates elimination of potassium by the kidneys. Alcohol, coffee
(and caffeine drinks), sugar, and diuretic drugs, however, cause potassium
losses and can contribute to lowering the blood potassium. This mineral is also
lost with vomiting and diarrhea.
Sources:
Potassium is found in a wide range of foods. Many
fruits and vegetables are high in potassium and low in sodium and, as
discussed, help prevent hypertension. Most of the potassium is lost when
processing or canning foods, while less is lost from frozen fruits or
vegetables.
Leafy green vegetables such as spinach, parsley,
and lettuce, as well as broccoli, peas, lima beans, tomatoes, and potatoes,
especially the skins, all have significant levels of potassium. Fruits that
contain this mineral include oranges and other citrus fruits, bananas, apples,
avocados, raisins, and apricots, particularly dried. Whole grains, wheat germ,
seeds, and nuts are high-potassium foods. Fish such as flounder, salmon,
sardines, and cod are rich in potassium, and many meat foods contain even more
potassium than sodium, although they often have additional sodium added as
salt. Potassium may also be obtained from the following herbs: red clover,
sage, catnip, hops, horsetail, nettle, plantain and skullcap. Caffeine and
tobacco reduce the absorption of potassium. People at risk for insufficient
potassium intake include alcoholics, drug addicts and crash dieters.
Functions:
Potassium is very important in the human body.
Along with sodium, it regulates the water balance and the acid-base balance in
the blood and tissues. Potassium enters the cell more readily than does sodium
and instigates the brief sodium-potassium exchange across the cell membranes.
In the nerve cells, this sodium-potassium flux generates the electrical
potential that aids the conduction of nerve impulses. When potassium leaves the
cell, it changes the membrane potential and allows the nerve impulse to
progress. This electrical potential gradient, created by the
"sodium-potassium pump," helps generate muscle contractions and
regulates the heartbeat. Another of the pump's most important functions is
preventing the swelling of cells. If sodium is not pumped out, water
accumulates within the cell causing it to swell and ultimately burst.
Potassium is very important in cellular
biochemical reactions and energy metabolism; it participates in the synthesis
of protein from amino acids in the cell. Potassium also functions in
carbohydrate metabolism; it is active in glycogen and glucose metabolism,
converting glucose to glycogen that can be stored in the liver for future
energy. Potassium is important for normal growth and for building muscle.
Though sodium is readily conserved by the body,
there is no effective method for potassium conservation. Even when a potassium
shortage exists, the kidneys continue to excrete it. Because the human body
relies on potassium balance for a regularly contracting heart and a healthy
nervous system, it is essential to strive for this electrolyte's balance.
Uses:
In medicine, potassium is one of the most
commonly prescribed minerals. It is also commonly measured in biochemical
testing and is supplemented if it is low. Because potassium is crucial to
cardiovascular and nerve functions and is lost in diuretic therapy for edema or
hypertension, a prevalent American disease, it must be added as a dietary
supplement frequently. As stated before, the average American diet has reversed
the natural high potassium-low sodium intake, and a shift back to this more
healthful balance will help reduce some types of elevated blood pressure. Supplementing
potassium can be helpful in treating hypertension specifically caused by a
hyper-response to excess sodium.
In one study, 37 adults with mild hypertension
participated in a crossover study. Patients received either 2.5 g of potassium
per day, 2.5 g of potassium plus 480 mg of magnesium, or a placebo for eight
weeks. They were then crossed-over to receive a different treatment for another
eight weeks and so on. The results of the study demonstrated that potassium
supplementation lowered systolic blood pressure from an average of 12 mm Hg and
diastolic blood pressure an average of 16 mm Hg. Interestingly, the additional
magnesium offered no further reduction in blood pressure.
Potassium supplementation may be especially
useful in the treatment of high blood pressure in persons over the age of 65.
The elderly often do not fully respond to blood pressure-lowering drugs making
the use of potassium supplement an exciting possibility. In one double-blind
study, 18 untreated elderly patients (average age 75 years) with systolic blood
pressure of greater than 160 mm Hg and/or a diastolic blood pressure of greater
than 95 mm Hg were given either potassium chloride (supplying 2.5 g of
potassium) or a placebo each day for four weeks. After this relatively short treatment
period the group getting the potassium experienced a drop of 12 mm Hg in
systolic and 7 mm Hg in diastolic blood pressure. These results compare quite
favorably to the reduction of blood pressure produced by drug therapy in the
European Working Party on High Blood Pressure in Elderly Study.
Pharmacological preparations of potassium are
commonly prescribed for many of these conditions. A 10 percent potassium
chloride solution is often given, but its taste is unpleasant. More easily used
formulas are tablets that are swallowed or effervescent tablets. K-Lor, Slow-K,
K-Lyte, and Kaochlor are common preparations. Time-release formulas such as
Micro-K are also available.
Potassium chloride has occasionally been helpful
in treating infant colic, some cases of allergies, and headaches. During and
after diarrhea, potassium replacement may be necessary, and many people feel
better taking potassium during weight-loss programs. Fatigue or weakness,
especially in the elderly, is often alleviated with supplemental potassium,
along with magnesium. Additional potassium may also be required for dehydration
states after fluid losses and may be used to prevent or reduce hangover
symptoms after alcohol consumption.
Deficiency and Toxicity:
Elevations or depletions of this important
mineral can cause problems and, in the extreme, even death. Maintaining
consistent levels of potassium in the blood and cells is vital to body
function.
Even with high intakes of potassium, the kidneys
will clear any excess, and blood levels will not be increased. For elevated
potassium levels, called hyperkalemia, to occur, there must usually be other
factors involved; decrease in renal function is the most likely cause. Major
infection, gastrointestinal bleeding, and rapid protein breakdown also may
cause elevated potassium levels. Cardiac function is affected by hyperkalemia;
electrocardiogram changes can be seen in this condition.
Deficiency of potassium is much more common,
especially with aging or chronic disease. Some common problems that have been
associated with low potassium levels include hypertension, congestive heart
failure, cardiac arrhythmia, fatigue, and depression and other mood changes.
Many factors reduce body levels of potassium. Diarrhea, vomiting, and other
gastrointestinal problems may rapidly reduce potassium. Infants with diarrhea
must be watched closely for low blood potassium, termed hypokalemia. Diabetes
and renal disease may cause low as well as high potassium levels.
Several drugs can cause hypokalemia-diuretic therapy
is of most concern; long-term use of laxatives, aspirin, digitalis, and
cortisone may also deplete potassium. Heat waves and profuse sweating can cause
potassium loss and lead to dehydration, with potassium leaving the cells along
with sodium and being lost in the urine. This can generate some of the symptoms
associated with low potassium; most people are helped rapidly with potassium
supplements or potassium-rich foods. People who consume excess sodium can lose
extra urinary potassium, and people who eat lots of sugar also may become low
in potassium.
Fatigue is the most common symptom of chronic
potassium deficiency. Early symptoms include muscle weakness, slow reflexes,
and dry skin or acne; these initial problems may progress to nervous disorders,
insomnia, slow or irregular heartbeat, and loss of gastrointestinal tone. A
sudden loss of potassium may lead to cardiac arrhythmia Low potassium may
impair glucose metabolism and lead to elevated blood sugar. In more severe
potassium deficiency, there can be serious muscle weakness, bone fragility,
central nervous system changes, decreased heart rate, and even death.
Potassium is the most commonly measured blood
mineral in medicine, and deficiencies must be watched for carefully and treated
without delay with supplemental potassium.
Requirements:
There is no specific RDA for potassium, though it
is thought that at least 2-2.5 grams per day are needed, or about 0.8-1.5 grams
per 1,000 calories consumed. The average American diet includes from 2-6 grams
per day.
In cooking or canning foods, potassium is
depleted but sodium is increased, as it is in most American processed foods as
well. It is suggested that we include more potassium than sodium in our diets;
a ratio of about 2:1 would be ideal. When we increase sodium intake, we should
also consume more potassium-rich foods or take a potassium supplement.
Prescribed potassium replacement
Over-the-counter potassium supplements usually
contain 99 mg. per tablet. Prescription potassium is usually measured in
milliequivalents (mEq.); 1 mEq. equals about 64 mg. About 10-20 mEq. (640-1280
mg.) per day may be recommended as a supplement to the individual's diet.
The inorganic potassium salts are found as the
sulfate, chloride, oxide, or carbonate. Organic salts are potassium gluconate,
fumarate, or citrate. These organic molecules are normally part of our cells
and body tissues. Potassium liquids and salt substitutes containing potassium
chloride (KCl) are other ways to obtain additional sources of this mineral.
Potassium is well absorbed, so it is available to the body in most forms.
