by Elson M. Haas, M.D.
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.
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.
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.
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.
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.
Copyright 2000 Elson M. Haas, M.D.
Used with Permission