2 little? 2 nutrients to get more of.
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. (1) Recent meta-analyses have echoed his findings. (2,3)
"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. (2)
"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. (4)
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. (2)
With evidence mounting, the World Health Organization and the American Heart Association have advised people to get potassium from foods, especially fruits and vegetables. (5,6) (See "Potassium on Tap," p. 10.)
"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. (7)
"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."
In theory, you could get potassium from a supplement or a (potassium chloride) salt substitute. You could also get it from foods that replace some salt (sodium chloride) with potassium chloride. Odds are, more of those foods will start popping up on shelves if the Food and Drug Administration goes ahead with its proposal to require potassium numbers on Nutrition Facts labels.
"Supplements are extraordinarily safe as long as you don't have kidney disease and aren't taking a drug that interferes with potassium excretion in the kidney," says Whelton. "If you're taking an ACE inhibitor for high blood pressure, for example, you should consult your physician."
But there's no need to talk to your doctor about eating more fruits and vegetables. And getting potassium from produce has another advantage: it may protect your bones. Why?
"Potassium-rich fruits and vegetables generate alkali in the body," says Bess Dawson-Hughes, director of the Bone Metabolism Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University.
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. (8) 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. (9)
"We estimated that they were getting a little over 8 servings of fruits and vegetables and 5 1/2 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." (10)
(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 5 1/2 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.'"
People know that losing excess weight and eating less sugar may lower their risk of type 2 diabetes. But few know that getting enough magnesium may also ward off the disease.
"In one observational study after another, we see that a higher magnesium intake is associated with a lower incidence of type 2 diabetes," says Adela Hruby, a research fellow at the Harvard School of Public Health.
For example, when she and her colleagues followed roughly 2,500 participants in the Framingham Heart Study for seven years, those who consumed the most magnesium (around 400 milligrams a day) had about half the risk of type 2 diabetes of those who consumed the least (around 240 mg). (11)
"We looked at people who were initially healthy and also at people who were prediabetic, so they were at higher risk," explains Hruby. "Magnesium appeared to be particularly beneficial for those with higher than normal blood sugar when they entered the study."
And it's not just Framingham. After looking at 13 studies on more than 536,000 people, researchers estimated that the risk of diabetes was 14 percent lower for every 100 mg of magnesium the people consumed. (12)
But something else about people who eat more magnesium could explain why they have a lower risk of diabetes. So scientists do trials to see if giving people magnesium lowers their blood sugar or insulin.
"In some studies on people who have metabolic syndrome or prediabetes, magnesium lowers fasting blood glucose or insulin or HbAlc," notes Hruby. (Hemoglobin Ale is a long-term measure of blood sugar levels.)
But not all studies agree. (13) What's more, "there haven't been sufficient numbers of trials in humans," says Hruby. "That is really the bottom line."
How might magnesium help prevent diabetes? "It might help beta-cells in the pancreas secrete insulin," says Hruby. "And it may also make cells more sensitive to insulin, so that your muscles and other tissues respond better to it."
Millions of people get less magnesium than experts recommend. (7)
"Fifty percent of the country is underconsuming magnesium," notes Hruby. But that doesn't mean they're deficient. "We don't have great data on magnesium levels in the body," she adds.
Fortunately, most magnesium-rich foods are healthy. And a growing body of evidence suggests that people who get more magnesium have a lower risk of stroke and heart disease. (14,15)
"Magnesium is at the heart of the chlorophyll molecule, so every leafy green has it," explains Hruby. "Whole grains and beans are also good sources. My favorite sources happen to be chocolate and coffee."
In fact, an 8 oz. cup of coffee has only 7 mg. But a 1 oz. shot of espresso, which is more concentrated, has 24 mg. (Cappuccinos, lattes, mochas, and macchiatos are typically made with espresso.)
And taking a magnesium supplement has a drawback: more than 350 mg a day from pills may cause diarrhea. "You can't get too much magnesium from foods," adds Hruby.
What's more, if it's not magnesium but something else in beans, leafy greens, whole grains, and coffee that protects your health, you won't get it from a pill.
(1) JAMA 277-1624, 1997.
(2) BMJ 2013. doi:10.1136/bmj.f1378.
(3) J. Hum. Hypertens. 17: 471,2003.
(4) Hypertension 55: 681, 2010.
(5) who.int/nutrition/publications/guidelines/ potassium_intake_printversion.pdf.
(6) Stroke 45: 3754, 2014.
(7) www.health.gov/dietaryguidelines/ 2015-BINDER/meeting2/docs/refMaterials/ Usual_lntake_072013.pdf.
(8) J. Clin. Endocrinol. Metab. 94: 96, 2009.
(9) J. Bone Min. Res. 2015. doi:10.1002/ jbmr.2554.
(10) J. Nutr. 133: 3130, 2003.
(11) Diab. Care 37: 419, 2014.
(12) Diab. Care 34: 2116, 2011.
(13) Diab. Med. 23:1050, 2006.
(14) Int. J. Cardiol. 796:108, 2015.
(15) J. Am. Heart Assoc. 2: e000114, 2013.
Potassium on Tap Most people get less potassium than experts recommend (4,700 mg a day). Go for fruits and vegetables so you can eat bigger servings-the ones below are small-without piling on calories ... as Potassium Calories (mg) Baked potato with skin (1 small) 130 750 Clams (4 oz. cooked) 170 710 Beet greens (% cup cooked) 20 650 Halibut (4 oz. cooked) 130 600 Yellowfin tuna (4 oz. cooked) 150 600 Sweet potato with skin (1 small) 130 540 Wild Coho salmon (4 oz. cooked) 160 490 Swiss chard (% cup cooked) 20 480 Lima beans (% cup cooked) 110 480 Acorn squash (% cup cooked) 60 450 Farmed Atlantic salmon (4 oz. cooked) 230 440 Non-fat plain yogurt (6 oz.) 100 430 Spinach (1/2 cup cooked) 20 420 Banana (1) 110 420 Low-fat plain yogurt (6 oz.) 110 400 Dried apricots (1/4 cup) 80 380 Fat-free milk (1 cup) 80 380 Cantaloupe (1/4) 50 370 Lentils (1/2 cup cooked) 120 370 Pinto beans (1/2 cup cooked) 120 370 Tomato sauce (1/2 cup) 30 360 Kidney beans (1/2 cup cooked) 110 360 Avocado (1/2 cup) 120 360 Great Northern beans (1/2 cup cooked) 100 350 Prunes (Va cup) 110 350 Navy beans (1/2 cup cooked) 130 350 Spinach (2 cups raw) 10 340 Shelled edamame (1/2 cup cooked) 100 340 Pacific cod (4 oz. cooked) 100 330 Tomato paste (2 Tbs.) 30 320 Pistachios (1/4 cup) 170 310 Low-fat fruit yogurt (6 oz.) 170 300 Tomato (1) 20 290 Butternut squash (Z2 cup cooked) 40 290 Peach or nectarine (1) 60 290 Raisins (1/4 cup) 110 270 Boston or bibb lettuce (2 cups raw) 10 260 Beets (1/2 cup cooked) 40 260 Brussels sprouts (1/2 cup cooked) 30 250 Artichoke hearts (1/2 cup cooked) 50 240 Orange (1) 70 240 Apple (1) 100 200 Crapes (1 cup) 60 180 Sources: USDA and manufacturers. The Bottom Line A diet based on the DASH & OmniHeart studies is rich in potassium (4,700 mg) and magnesium (500 mg). Bonus: it protects your arteries (see March 2015, p. 1). Here's a 2,100-calorie version. Daily Servings Vegetables & Fruit 11 (1/2 cup, 1 cup greens, 1 piece fruit) Grains 4 (1/2 cup pasta or rice or cereal, 1 slice bread) Low-fat Dairy 2 (1 cup milk or yogurt, 1/2 oz. cheese) Legumes & Nuts 2 (1/2 cup beans, 1/4 cup nuts, 1/4 oz. tofu) Poultry, Fish, Lean Meat 1 (1/4 lb., cooked) Oils & Fats 2 (1 Tbs.) Desserts & Sweets 2 (1 tsp. sugar, 1 small cookie) Wild Card 1 Poultry, Meat, Fish OR Oils & Fats OR Grains OR Desserts & Sweets Mining Magnesium Women should shoot for 320 milligrams of magnesium a day. Men should aim for 420 mg. Rule of thumb: go for beans, greens, whole grains, and nuts. Magnesium Calories (mg) Pumpkin seed kernels (1/4 cup) 180 190 Brazil nuts (1/4 cup) 220 125 Kellogg's All-Bran Original cereal (1/4 cup) 80 100 Almonds (1/4 cup) 210 95 Cashews (1/4 cup) 200 90 Spinach (1/2 cup cooked) 20 80 Swiss chard (1/4 cup cooked) 20 75 Peanuts (1/4 cup) 210 65 Black beans (1/2 cup cooked) 110 60 Quinoa (1/2 cup cooked) 110 60 Dark chocolate (1.4 oz.) 220 60 Peanut butter (2 Tbs.) 190 55 Flazelnuts (1/4 cup) 210 55 Beet greens (1/2 cup cooked) 20 50 Shelled edamame (1/2 cup cooked) 100 50 Navy beans (1/2 cup cooked) 130 50 Yellowfin tuna (4 oz. cooked) 150 50 Spinach (2 cups raw) 10 45 Oat bran (1/2 cup cooked) 40 45 Black-eyed peas (1/2 cup cooked) 100 45 Great Northern beans (1/2 cup cooked) 100 45 Pinto beans (1/2 cup cooked) 120 45 Semisweet chocolate (1.4 oz.) 190 45 Walnuts (1/4 cup) 200 45 Firm tofu (4 oz.) 80 40 Brown rice (1/2 cup cooked) 110 40 Kidney or Lima beans (1/2 cup cooked) 110 40 Garbanzo beans (1/2 cup cooked) 130 40 Sunflower seed kernels (1/4 cup) 190 40 Lentils (1/2 cup cooked) 120 35 Pistachios (1/4 cup) 170 35 Okra (1/2 cup cooked) 20 30 Bulgur (1/2 cup cooked) 80 30 Oatmeal (1/2 cup cooked) 80 30 Post Shredded Wheat Original (1/2 cup) 90 30 Haddock (4 oz. cooked) 100 30 Non-fat plain yogurt (6 oz.) 100 30 Low-fat plain yogurt (6 oz.) no 30 Halibut (4 oz. cooked) 130 30 Fat-free milk (1 cup) 80 25 Canned light tuna in water (4 oz.) 100 25 Whole wheat bread (1 slice, 1 oz.) 70 20 Low-fat fruit yogurt (6 oz.) 170 20 Daily Value (DV): 400 mg. Sources: USDA and manufacturers.
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|Title Annotation:||SPECIAL FEATURE|
|Publication:||Nutrition Action Healthletter|
|Date:||Sep 1, 2015|
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