If you're a close reader of nutrition labels, you may have noticed that a small but growing number of foods now list how much potassium they contain.
The Food and Drug Administration doesn't require food producers to reveal this information, but "there's both consumer and industry interest to provide potassium information on a voluntary basis," notes Robert Earl, senior director of nutrition policy at the Food Products Association, which represents food processors.
That's because in recent years several well-regarded groups -- the U.S. Dietary Guidelines Advisory Committee, the National Academy of Sciences' Food and Nutrition Board and the National Heart, Lung, and Blood Institute (NHLBI) -- have underscored the health benefits of potassium and the risks of not getting enough of this nutrient.
Besides, the food industry has been criticized for adding too much salt to many products. High blood pressure is a problem that afflicts nearly one in three adults in the United States, according to the American Heart Association. Studies show that a potassium-rich diet can help counter the hypertensive effects of eating too much sodium.
How much potassium do you need daily? The National Academy of Sciences says 4,700 milligrams daily is adequate for adults. But men routinely consume only about two-thirds of that, and women get about half, according to a 2004 study cited in a report from the dietary guidelines committee.
"Our diet is remarkably different from what we evolved on," says Lawrence Appel, professor of medicine at Johns Hopkins Medical Institutions in Baltimore who has examined potassium's importance in the human diet. "We evolved on a low-sodium, high-potassium diet. Now we eat a high-sodium, low-potassium diet. This flip may be in part responsible for many of the [health] problems that are commonplace today."
Besides high blood pressure, count among those possible problems stroke, kidney stones and osteoporosis -- one of the major causes of broken bones in the elderly and a frequent reason for admission to nursing homes. Potassium protects health by blunting salt sensitivity, regulating blood pressure, keeping the heart at a steady beat and muting calcium loss from bones.
While you can eat food fortified with potassium, sprinkle potassium chloride in place of table salt or take dietary supplements with potassium, "you can get all the potassium you need through foods," Appel says. Most adults can meet their needs by consuming two cups of fruit, 21/2 cups of vegetables and three glasses of milk, preferably low-fat or nonfat daily. In fact, studies show that the Dietary Approach to Stopping Hypertension (DASH) eating plan developed by NHLBI supplies all the potassium needed daily. (Find DASH free online at www.nhlbi.nih.gov/health/public/heart/hbp/dash/index.htm.)
Naturally occurring potassium seems to cover the health bases better than potassium chloride fortification alone, which only appears to offer protection against salt sensitivity and high blood pressure, not against kidney stones or bone loss.
There's another drawback to taking potassium supplements or sprinkling potassium chloride on your food: These steps could be harmful for those who have kidney damage or who take blood-pressure-lowering drugs known as angiotensin converting enzyme (ACE) inhibitors. "If you have problems with kidney function or are taking medication to lower blood pressure, check with your doctor before increasing your potassium intake," Appel says.
National nutritional surveys conducted by the federal government show that milk, white potatoes, coffee, beef, tomatoes, orange juice and grapefruit juice are among the leading sources of potassium in the American diet. But the more varied the diet -- and the less processed food eaten -- the higher the potassium intake. Here are a few other potassium-rich options:
Have a sweet potato. One baked sweet potato contains nearly 700 milligrams of potassium, twice that found in six ounces of orange juice.
Dig into some cooked greens. A cup of cooked beet greens provides about a quarter of a day's worth of potassium and clocks in at just 40 calories -- less than the calories found in half a cup of grapefruit juice. A cup of cooked spinach provides nearly as much -- about 20 percent of the daily intake.
Toss some white beans on your salad. And while you're at it, add edamame, green soybeans and some tuna. About half a cup of soybeans, half a cup of white beans and three ounces of tuna together provide about a third of the daily adequate intake for potassium.
Snack on yogurt. An eight-ounce container of plain low-fat yogurt has more than 500 milligrams of potassium. Add a banana (422 milligrams) and you'll get nearly 20 percent of the daily intake. Other good high-potassium snack options are apricots, peaches, prunes, cantaloupes and honeydew melons.
Dine on fish. Cod, halibut, clams, rockfish and rainbow trout are also packed with potassium, providing about 10 percent of the daily intake per three-ounce serving.
Sip tomato juice. Or add some tomato-based spaghetti sauce regularly to your fare. Tomato products are rich sources of potassium. Just be sure to choose canned low-sodium tomato products since the standard tomato products in cans and jars are generally high in sodium and could undermine your efforts.
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