December 2012 Issue

Increasing Dietary Potassium — Find Out Why Most People Need to Consume More of This Mineral
By Linda Antinoro, RD, JD, LDN, CDE
Today’s Dietitian
Vol. 14 No. 12 P. 50

Did you know that many of your clients may not be getting enough potassium in their diet?

According to the 2010 Dietary Guidelines, individuals should be taking in 4,700 mg/day, except for those who have hyperkalemia due to renal disorders or who are taking certain medications. It’s estimated that the average US dietary intake of potassium is 1,755 mg/day.1 A recent article in The American Journal of Clinical Nutrition highlighting data from the National Health and Nutrition Examination Survey found that fewer than 2% of US adults met the daily 4,700 mg recommendation.2

The dearth of potassium in the typical American diet is troublesome given this mineral’s role in controlling the electrical activity of the heart, regulating acid-base balance, building muscle, and synthesizing proteins. Research suggests consuming an optimal amount of potassium may protect against cardiovascular ailments, muscle wasting, osteoporosis, and kidney stones.

Cardiovascular Protection
Scores of studies have linked potassium with lower blood pressure. It seems to have this effect by activating nitric oxide release, which promotes vasodilation. Other possible mechanisms include promoting natriuresis or the excretion of sodium in the urine, reducing vasoconstrictive sensitivity to norepinephrine and angiotensin II, improving insulin sensitivity, and decreasing oxidative stress and inflammation.1

Mark Houston, MD, MS, an associate clinical professor of medicine at Vanderbilt Medical School and director of the Hypertension Institute at St Thomas Hospital in Tennessee, says if individuals increased their potassium intake to recommended levels, hypertension among adults could be reduced by 10%, adding that he even advocates for getting 5,000 mg/day.

As mentioned, potassium’s perks go beyond lowering blood pressure. In one study involving more than 12,000 adults, high potassium intake was associated with a 20% decreased risk of dying from all causes.3 Those who consumed 4,069 mg of potassium per day had a 37% and 49% lower risk of death from cardiovascular disease and ischemic heart disease, respectively, compared with those who took 1,793 mg/day.3

“Though potassium was a consistent and strong predictor of mortality in our study, like other studies, the sodium-potassium ratio showed a stronger relationship with mortality than either sodium or potassium alone,” says Elena Kuklina, MD, PhD, an epidemiologist with the Centers for Disease Control and Prevention. Houston agrees: “An increase in potassium intake along with a decrease in sodium intake is the most important dietary change—aside from weight management—that a person can make to reduce their risk of cardiovascular disease.”

Risk of stroke also decreases with greater potassium intake. A meta-analysis of 10 prospective studies observed a statistically significant inverse association between potassium intake and stroke risk.4 For every 1,000 mg increase in potassium intake, ischemic stroke risk decreased by 11%.4

Moreover, improved blood vessel function and reduced left ventricular hypertrophy are apparent with optimal potassium intake. In a small study of 42 people with mildly raised blood pressure who were already consuming approximately 2,200 mg of potassium from dietary sources, the addition of an extra 2,500 mg through supplements for four weeks significantly improved endothelial function, increased large elastic artery compliance (a gauge of how well arteries widen and allow blood flow), reduced left ventricular mass, and improved left ventricular diastolic function compared with placebo.5 In another study involving mostly normotensive young adults, protection against greater left ventricular mass was seen in those consuming more potassium and less sodium.6 These findings suggest potassium may have a preventive role in cardiovascular health even in the absence of hypertension.

Muscle Wasting
In addition to being cardioprotective, high potassium intake appears to defend against the loss of muscle mass associated with aging. Findings from a study show participants who had a potassium intake of 5,266 mg/day from fruits and vegetables averaged 3.6 more pounds of lean tissue mass than those with one-half that potassium intake.7 This is noteworthy given this amount of lean tissue is almost as great as the amount of muscle that’s lost over a decade in older adults.

The researchers contend it’s the alkaline diet that potassium-rich produce provides that relieves metabolic acidosis caused by eating the typical American diet, which frequently contains high-protein foods, cereal grains, and other acid-producing foods. These high acidic foods promote nitrogen excretion and muscle wasting. Consuming ample dietary potassium through a plethora of fruits and vegetables has the potential to protect against chronic muscle wasting or sarcopenia, characterized by the progressive loss of muscle mass, function, quality, and strength that can contribute to mobility issues, osteoporosis, falls and fractures, frailty, and loss of physical function and independence.8

Osteoporosis
The alkaline environment that protects against muscle wasting also may help preserve bone mineral density. The neutralization of acids in the body, which results from eating a more alkaline diet, curtails calcium excretion and, theoretically, should benefit bone health. Yet clinical trials linking potassium to greater bone density remain inconsistent, with some studies showing increases in bone density with high potassium intake and others showing no significant change in bone density or any markers of bone turnover.

Kidney Stones
The decrease in calcium excretion due to an increase in potassium intake also may reduce the risk of kidney stones. Two well-known prospective studies—the Health Professionals Follow-Up Study and the Nurses’ Health Study—support this finding.9,10 In the Health Professionals Follow-Up Study, 45,000 men who consumed more than 4,000 mg of potassium per day were only one-half as likely to develop kidney stones as those who averaged less than 2,895 mg/day.9 Of the 90,000 women in the Nurses’ Health Study who took 3,458 mg of potassium per day (the highest intake), only 65% were as likely to develop symptomatic kidney stones as women who took 2,703 mg/day (the lowest intake).10

Preferred Potassium Sources
As dietitians already know, choosing potassium-rich foods is the best way clients should increase intake of this mineral. This is highlighted in the 2010 Dietary Guidelines for Americans, which state that potassium is a nutrient of public health concern and discourage individuals from using supplements to meet daily recommendations. High-dose potassium supplements can disrupt heart rhythms and be dangerous to clients who don’t know the status of their kidney function. Steer clients away from experimenting with potassium supplements, as they should take them only under their physician’s supervision.

While meat, fish, poultry, beans, nuts, and dairy foods provide potassium, consuming ample fruits and vegetables is the best way to boost intake because they contain potassium citrate, the form that offers greater alkalinity. Fortunately, winter produce and some of the items on your clients’ holiday menus are packed with this powerful mineral.

— Linda Antinoro, RD, JD, LDN, CDE, is a freelance writer and part of the Nutrition Consultation Service at Brigham and Women’s Hospital in Boston.

 

References
1. Houston MC. The importance of potassium in managing hypertension. Curr Hypertens Rep. 2011;13(4):309-317.

2. Cogswell ME, Zhang Z, Carriquiry AL, et al. Sodium and potassium intakes among US adults: NHANES 2003-2008. Am J Clin Nutr. 2012;96(3):647-657.

3. Yang Q, Liu T, Kuklina EV, et al. Sodium and potassium intake and mortality among US adults: prospective data from the Third National Health and Nutrition Examination Survey. Arch Intern Med. 2011;171(13):1183-1191.

4. Larsson SC, Orsini N, Wolk A. Dietary potassium intake and risk of stroke: a dose-response meta-analysis of prospective studies. Stroke. 2011;42(10):2746-2750.

5. He FJ, Marciniak M, Carney C, et al. Effects of potassium chloride and potassium bicarbonate on endothelial function, cardiovascular risk factors, and bone turnover in mild hypertensives. Hypertension. 2010;55(3):681-688.

6. Rodriquez CJ, Bibbins-Domingo K, Jin Z, Daviglus ML, Goff DC Jr, Jacobs DR Jr. Association of sodium and potassium intake with left ventricular mass: coronary artery risk development in young adults. Hypertension. 2011;58(3):410-416.

7. Dawson-Hughes B, Harris SS, Ceglia L. Alkaline diets favor lean tissue mass in older adults. Am J Clin Nutr. 2008;87(3):662-665.

8. Aging in motion: the facts about sarcopenia. Alliance for Aging Research website. http://www.aginginmotion.org/wp-content/uploads/2011/04/sarcopenia_fact_sheet.pdf. Updated April 2011. Accessed March 19, 2012.

9. Curhan GC, Willett WC, Rimm EB, Stampfer MJ. A prospective study of dietary calcium and other nutrients and the risk of symptomatic kidney stones. N Engl J Med. 1993;328(12):833-838.

10. Curhan GC, Willett WC, Speizer FE, Spiegelman D, Stampfer MJ. Comparison of dietary calcium with supplemental calcium and other nutrients as factors affecting the risk for kidney stones in women. Ann Intern Med. 1997:127(7):497-504.

 

Potassium Amounts in Produce
The amounts listed below range from highest to lowest in milligrams. All servings are 1 cup and vegetables are cooked unless otherwise noted.


Food

Potassium Content (mg)

Swiss chard, chopped

961

Lima beans, large, mature seeds

955

Acorn squash, cubed

896

Spinach

839

White potato, baked with skin (1 medium)

751

Butternut squash, cubed

582

Parsnips

572

Pumpkin, mashed

564

Kohlrabi

561

Tomato juice, unsalted

556

Sweet potato, baked with skin (1 medium)

542

Medjool dates (3)

501

Banana  (1 medium)

422

Apricots, dried, uncooked halves (1/4 cup)

378

Rutabagas, cubed

367

Artichoke (1 medium)

343

Orange (1 large)

333

Raisins (1/4 cup)

272

— Source: USDA National Nutrient Database for Standard Reference, Release 25