Bananas, tomatoes, oranges, cantaloupe, peaches, spinach, Swiss chard, lima beans, potatoes–these are some of the world’s healthiest foods, in part because they are excellent sources of potassium.
Potassium is an important mineral, one of a class known as electrolytes. When dissolved in water, electrolytes conduct electricity needed for nerves and muscles to do their work. You may have heard of electrolytes through sports drinks designed to replenish electrolytes used up during vigorous exercise. But they are also obtained from regular foods.
Both nerves and muscles need a good supply of potassium. The mineral plays a role in the storage of carbohydrates in the muscles for endurance activities, and it helps regulate the body’s fluid balance and blood pressure. When there is insufficient potassium, nerves and muscles fail to function as they should, and the heart (the body’s most important muscle) may lose its ability to stay in normal rhythm.
About one of every five Americans admitted to a hospital has a potassium deficiency. And a large meta-analysis published in 2011 concluded that increasing potassium intake by 1.64 grams a day could result in 1.15 million fewer stroke deaths a year worldwide while also reducing the risk of heart disease.
The good news is that it’s easy to get the potassium you need just by eating a balanced diet. And you should not take potassium supplements on your own without first talking to your doctor since having too much potassium can be as dangerous as having too little.
A dangerously low level of potassium (known as hypokalemia) is rarely caused by diet alone unless you have anorexia, bulimia, alcoholism or a kidney disorder. You’re also susceptible if you’ve had bariatric surgery or take medications such as some diuretics.
More Potassium, Less Sodium
Most Americans, however, do not consume as much potassium as they should. The Institute of Medicine, in a recent report, recommended intake of 4.7 grams a day, but most American adults consume less than half that amount...and African Americans even less.
One major benefit from consuming more potassium, according to the report, is to blunt the effect of too much sodium, another important electrolyte. Ideally, a person should consume more potassium than sodium (some experts recommend a 5:1 ratio). But Americans actually get about twice as much sodium, and this imbalance is believed to be a major factor in hypertension and other heart problems.
An enzyme-based transport mechanism known as the potassium-sodium pump is charged with the duty of moving potassium and sodium in opposite directions across cell membranes. Three sodium ions are pumped out for every two potassium ions pumped in. This pumping action is particularly important for nerve cells as they transmit impulses to working muscles.
A proper balance of sodium and potassium is essential. Too much or too little of either can cause cells to malfunction and, in extreme cases, lead to serious problems and even death. In healthy persons not taking medications, the latter are rare, but less extreme imbalances are common.
Mainly through the kidneys, the body takes care of electrolyte imbalances. Eat too much salt, and you get thirsty. As you drink more water, the sodium is diluted, and your kidneys are signaled to hang onto water. This extra fluid in the cells, though, creates more work for the heart, and the result over time is hypertension.
The formula is well documented: more sodium equals higher blood pressure. Older persons, African Americans and diabetics are particularly sensitive to the effects of too much salt. Treatment with diuretic medications helps rid the body of excess sodium but the right formulation must be found to avoid having too much potassium excreted at the same time.
The Third National Health and Nutrition Survey (NHANES III), a large nationwide study published in the Archives of Internal Medicine [July 11, 2011] found that, over a 15-year period, higher sodium intake was associated with increased mortality from cardiovascular disease and all causes while higher potassium intake was associated with a lower risk of death.
“The major implications,” wrote the authors, “are that a diet balanced in both micronutrients is important.”
Most Americans know they should cut back on their sodium intake, but few actually do so, primarily because most of the sodium in the American diet comes from processed foods rather than the salt shaker.
A seven-ounce pork chop, for example, contains 680 milligrams of potassium and 122 milligrams of sodium. A similar portion of ham, on the other hand, is not only loaded with sodium (1,850 milligrams) but has a reduced level of potassium (480 milligrams).
Deli meats–even chicken and turkey–are cured and also have high concentrations of sodium relative to potassium. Canned goods and soups are notoriously high in sodium as are most restaurant meals.
But it’s at least as important to get an adequate amount of potassium, which is readily obtained from fresh fruits and vegetables, whole grains, legumes and dairy products.
The DASH diet that has been found effective in reducing hypertension calls for five servings a day of fruits and five a day of vegetables plus whole grains and low-fat dairy products. Combining the DASH diet with sodium restriction has been found even more effective.
Fresh fruits such as apricots, bananas, peaches and oranges are particularly good sources of potassium and excellent alternatives to salty snacks. Some vegetables such as spinach lose more than 50 percent of their potassium content during cooking. This, however, could be beneficial if this is leached off into a soup or stew.
It’s important not to try to improve your potassium:sodium ratio by taking potassium supplements without the advice of your doctor. For stroke prevention, studies have failed to find the same benefit from potassium obtained from supplements. And too much potassium (or too little sodium) can be even more dangerous than not enough. For that reason, persons taking potassium-sparing diuretics are advised not to use salt substitutes (which usually contain potassium chloride).
There is also no need to get hung up on laboriously counting milligrams of potassium. If you center your diet around fresh foods that you cook yourself, with at least five servings of fruits and vegetables, you’ll be getting the potassium you need.
REFERENCES:
Sonia M. Astle, R.N, MS, CCRN, “Restoring electrolyte balance,” RN/Thomsom Home Study Program CE Center, May, 2005.
Laurie Barclay, M.D., “Serum potassium may independently predict incident type 2 diabetes mellitus,” Medscape Medical News, October 29, 2010.
Caroline Cassels, “Potassium-sparing diuretics may cut Alzheimer’s risk,” Medscape Medical News, March 24, 2006.
John P. Cunha, DO, “Low potassium,” eMedicineHealth, last editorial review January 27, 2011.
“Electrolytes,” MedicineNet.com, last editorial review November 14, 2008.
Murray Epstein, M.D., and Jigiamg Wang, M.D., Ph.D., “The potassium phenomenon: hypertension in China,” Medscape Nephrology, August 4, 2011.
Susanna C. Larsson, Jarm Virtamo and Alicia Wolk, “Potassium, calcium, and magnesium intakes and risk of stroke in women,” American Journal of Epidemiology, 2011;174(1):35-43.
Lisa Nainggolan, “Boost potassium intake to cut stroke by 20%,” Heartwire, February 28, 2011.
Lisa Nainggolan, “Sodium/potassium ratio important for health,” Heartwire, July 11, 2011.
Lisa Nainggolan, “Call for increased potassium intake to lower BP, cut deaths,” Heartwire, September 14, 2010.
Amy Norton, “Potassium-rich diet tied to lower stroke risk,” Reuters Health, August 17, 2011.
“Potassium,” PubMed Health, National Library of Medicine, last reviewed September 1, 2010.
“Potassium in diet,” MedlinePlus, National Library of Medicine, updated by David Zieve, M.D., MHA, May 26, 2010.
Elizabeth Quinn, “Recommendations for water, sodium and potassium,” About.com Sports Medicine, February 6, 2008.
Steve Stiles, “Serum potassium targets in acute MI need rethink,” Heartwire, January 10, 2012.
Arian Sultan, M.D., et al, “Intravenous administration of magnesium and potassium solution lowers energy levels and increases success rates electrically cardioverting atrial fibrillation,” Journal of Cardiovascular Electrophysiology, 2012;23(1):54-59.
Lynda A. Szczech, M.D., MSCE, “The sodium-potassium seesaw: help patients balance,” Medscape Nephrology, February 27, 2012.
World’s Healthiest Foods, “Potassium.”
08/08/2012
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