Here's One of the Nutrients That Many of Us Get Too Little Of

Elli Quark

Too much salt. Too much sugar. Too much saturated fat. We often hear about what we get too much of. But we also get too little of some nutrients. Potassium is an important one that you’re better off getting from food than from a pill.

The power of potassium

Too much salt raises blood pressure. Most people know that. But far fewer know that getting enough potassium lowers blood pressure.

“The evidence is very strong and very consistent,” says Paul Whelton, a hypertension expert and professor of epidemiology at the Tulane School of Public Health and Tropical Medicine. “A higher potassium intake may blunt the effect of excess salt on blood pressure.” And most Americans get too much salt.

In  1997, Whelton combined the results of 29 trials that randomly assigned people to get high or low levels of potassium, largely from supplements. Recent meta-​analyses have echoed his findings. “They found a 3 to 5 point reduction in systolic blood pressure in those who got a potassium supplement,” he notes. “That’s not to be sneezed at.”

In people with hypertension who reached a total of 3,500 to 4,700 mg a day of potassium, the drop was 7 points.  “Potassium’s effect is bigger in people who have higher blood pressure, bigger in older people, and bigger in people who are consuming a lot of salt,” Whelton explains.

Potassium doesn’t just lower blood pressure. It may also make blood vessels less stiff, so they expand as the heart pumps blood through them.

What’s more, “a higher potassium intake is very closely linked to a lower risk of stroke,” says Whelton. In a recent meta-​analysis of nine studies, people who consumed the most potassium (3,500 to 4,700 mg a day) from foods had a 30 percent lower risk of stroke.

Health organizations are urging us to consume more potassium

With evidence mounting, the World Health Organization and the American Heart Association have advised people to get potassium from foods, especially fruits and vegetables.

“Citrus fruits, bananas, cantaloupe, prunes, apricots, raisins, and kiwi are all high in potassium,” notes Whelton, “as are all the dark green leafy vegetables, broccoli, beans, peas, squash, and tomatoes. And potato is a great source if you eat the skin.” Milk and yogurt are also good sources, he adds, as are nuts, soy foods, salmon, cod, flounder, and sardines.

The daily target is 4,700 milligrams, according to the National Academy of Medicine. But more than 95 percent of Americans get less than that. “The average is just over 3,000 mg a day for men and 2,300 mg a day for women,” says Whelton. “If we could just bump that up by  1,500 mg a day, we’d be doing pretty well.”

The superiority of the potassium found in fruits and vegetables

In fact, it’s not the potassium, but the citrate, malate, or other compounds that the potassium in fruits and vegetables is bound to, that makes the body produce alkali.

Why does alkali matter? “If you don’t have adequate alkali to balance the acid load from the grains and protein in a typical American diet, you lose calcium in the urine and you have bone loss,” says Dawson-Hughes. “When the body has more acid than it is easily able to excrete, bone cells get a signal that the body needs to neutralize the acid with alkali,” she explains. “And bone is a big alkali reservoir, so the body breaks down some bone to add alkali to the system.” Over time, those minute losses of bone and calcium can lead to osteoporosis, or brittle bones.

Unlike the potassium citrate, malate, etc., in fruits and vegetables, the potassium chloride in many supplements doesn’t stem bone loss.

How much fruit or vegetables do you need?

“In our recent trial, we identified people who were in the neutral range for net acid excretion—that is, they weren’t excreting acid or alkali, indicating that they were in pretty good balance,” notes Dawson-Hughes. “We estimated that they were getting a little over 8 servings of fruits and vegetables and 5½ servings of grain a day. After rounding, you come up with half as many servings of grains as fruits and vegetables.

“That’s close to the fruit-and-vegetable-to-grain serving ratio in the DASH diet. And when other researchers fed people a DASH diet, they saw reductions in bone loss markers similar to ours.” (The DASH—Dietary Approaches to Stop Hypertension—study, which was designed to lower blood pressure, is rich in fruits and vegetables, low in added sugars and refined grains, and includes fish, beans, nuts, oils, and low-fat dairy.)

“The ratio was just the reverse in people in our trial who had the most acid-producing diets,” adds Dawson-Hughes. “They ate 5½ servings of fruits and vegetables and just over 7 servings of grains.”

Just remember: a “serving” of grain is smaller than a restaurant bagel, tortilla, pizza crust, muffin, or bowl of pasta, rice, or cereal. Many restaurants serve not half a cup, but 3 or 4 cups, of spaghetti.

Protein also produces acid in the body, but people in the study who consumed more meat, poultry, fish, or dairy didn’t excrete more acid than those who ate less. “So we didn’t have to say that older people should eat less protein, which is important for their bone and muscle,” says Dawson-​Hughes. “Instead, we can just say, ‘Add some fruit and vegetables and drop some grains.’”

Some of the best sources of Potassium (milligrams)

Baked potato with skin (1 small) 750
Clams (4 oz. cooked) 710
Beet greens (½ cup cooked) 650
Halibut (4 oz. cooked) 600
Yellowfin tuna (4 oz. cooked) 600
Sweet potato with skin (1 small) 540
Wild Coho salmon (4 oz. cooked) 490
Swiss chard (½ cup cooked) 480
Lima beans (½ cup cooked) 480
Acorn squash (½ cup cooked) 450
Farmed Atlantic salmon (4 oz. cooked) 440
Non-fat plain yogurt (6 oz.) 430
Spinach (½ cup cooked) 420
Banana (1) 420
Low-fat plain yogurt (6 oz.) 400

Sources: JAMA 277: 1624, 1997; 2 BMJ 2013. doi:10.1136/bmj.f1378; J. Hum. Hypertens. 17: 471, 2003;Hypertension 55: 681, 2010;; Stroke 45: 3754, 2014;;Clin. Endocrinol. Metab. 94: 96, 2009; J. Bone Min. Res. 2015. doi:10.1002/jbmr.2554;Nutr. 133: 3130, 2003.


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