Why you need potassium -- and how much is too much, too little, or just right.
By Elizabeth M. Ward, MS, RD
Reviewed by Laura J. Martin, MD
Potassium is a key player in good health, but you may not be getting enough from food. Here's how potassium contributes to good health, and how to get the potassium you need.
Potassium is part of every cell in the body, and life would be impossible without it.
However, potassium is often taken for granted, in spite of its role in maintaining fluid balance, and keeping your brain, nerves, heart, and muscles functioning normally on a constant basis.
It's important to eat enough potassium every day to feel your best, and to help prevent certain chronic conditions. Falling short on potassium on a regular basis could jeopardize your long-term health in more ways that one.
Potassium Protects the Heart, Brain, and More
"Potassium in the diet lowers blood pressure. High blood pressure is the major risk factor for stroke and heart disease," says Lawrence Appel, MD, MPH, a professor of medicine, epidemiology, and international health at the Johns Hopkins Medical Institutions.
Appel, who has studied the effects of diet on blood pressure, tells WebMD that potassium may curb elevated blood pressure by contributing to more flexible arteries, and by helping the body get rid of excess sodium. Sodium promotes fluid retention, which may result in higher blood pressure.
Potassium may bolster bone strength by helping guard against bone loss, and it helps to reduce the risk for kidney stones.
Potassium's Partners in Better Blood Pressure
Potassium is important, but there's more to lowering blood pressure than a single mineral.
"Diets that include foods rich in potassium are associated with lower blood pressure, but it's not entirely accurate to give all the credit to potassium," says Marla Heller, MS, RD.
Appel has researched the effects of the Dietary Approaches to Stop Hypertension (DASH) diet on elevated blood pressure and found that it's capable of lowering blood pressure, often in a matter of weeks.
Heller, author of The DASH Diet Action Plan, says the relatively low-sodium DASH diet is based on large amounts of fruits and vegetables, low-fat and nonfat dairy, beans, nuts, seeds, whole grains, and lean meats, fish, and poultry.
Although the DASH diet is a treasure trove of potassium, it's also rich in calcium and magnesium, which help reduce blood pressure.
Experts suggest 4,700 milligrams of dietary potassium a day for adults as part of a balanced diet.
But average intake is lower for U.S. adults. Men average 3,200 milligrams per day of potassium, and women average 2,400 milligrams.
"Relying on convenience and restaurants foods and not eating enough fruits and vegetables is why so many people don't get enough potassium," Heller says. "Fresh and lightly processed foods, including dairy and meat, have the most potassium."
Home cooking determines potassium levels in produce, too.
Boiling depletes potassium. For example, a boiled potato has almost half the potassium of a baked potato. To preserve potassium, eat fruits and vegetables raw, or roast or lightly steam them.
When dining out, increase potassium by ordering a salad, extra steamed or roasted vegetables, bean-based dishes, fruit cups, and low-fat milk instead of soda.
Top Potassium Food Sources
Experts say food, not supplements, is the best way to meet potassium needs.
"My preference is food because potassium is found in foods that provide other nutrients, such as fiber, that also have beneficial health effects," Appel says.
Here's how many milligrams (mg) of potassium you'll get from these potassium-rich foods:
- Winter squash, cubed, 1 cup, cooked: 896 mg
- Sweet potato, medium, baked with skin: 694 mg
- Potato, medium, baked with skin: 610 mg
- White beans, canned, drained, half cup: 595 mg
- Yogurt, fat-free, 1 cup: 579 mg
- Halibut, 3 ounces, cooked: 490 mg
- 100% orange juice, 8 ounces: 496 mg
- Broccoli, 1 cup, cooked: 457 mg
- Cantaloupe, cubed, 1 cup: 431 mg
- Banana, 1 medium: 422 mg
- Pork tenderloin, 3 ounces, cooked: 382 mg
- Lentils, half cup, cooked: 366 mg
- Milk, 1% low fat, 8 ounces: 366 mg
- Salmon, farmed Atlantic, 3 ounces, cooked: 326 mg
- Pistachios, shelled, 1 ounce, dry roasted: 295 mg
- Raisins, quarter cup: 250 mg
- Chicken breast, 3 ounces, cooked: 218 mg
- Tuna, light, canned, drained, 3 ounces: 201 mg
Source: U.S. Department of Agriculture (USDA)
You May Need More or Less Potassium
Besides being linked to the potassium in your diet, potassium levels in your body are influenced by several factors, including kidney function, hormones, and prescription and over-the-counter medications.
People who take thiazide diuretics, often used to treat high blood pressure, may need more potassium. That's because thiazide diuretics promote potassium loss from the body. Steroids and laxatives also deplete potassium.
Other drugs used to lower blood pressure, including beta-blockers and ACE inhibitors, raise potassium levels in the body.
People with reduced kidney function may need to limit their daily potassium intake.
Ask your doctor or pharmacist about how all of the medications you take affect the potassium levels in your body, and if you need more, or less, of the mineral.
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Lawrence Appel, MD, MPH, professor of medicine, epidemiology, and international health, Johns Hopkins Medical Institutions.
Marla Heller, MS, RD, author, The DASH Diet Action Plan, Amidon Press, 2007.
U.S. Department of Agriculture: "Report of the Dietary Guidelines Advisory Committee Report on the Dietary Guidelines for Americans, 2010: Sodium, Potassium, and Water."
Appel, L. The New England Journal of Medicine, April 17, 1997; vol 336: pp 1117-1124.
Reviewed on September 22, 2010 © 2010 WebMD, LLC. All rights reserved.