Eat Less Salt & More Potassium to Live Longer, New Study Suggests

Bananas and Sweet Potatoes - High Potassium, Low Sodium FoodsA new study conducted by researchers at the US Centers for Disease Control and Prevention (CDC), Emory University School of Public Health, and Harvard School of Public Health, has found that a diet high in salt and low in potassium may increase risk of death from any cause by almost 50% and may result in twice the risk of death from heart attack, compared to a diet low in salt and high in potassium.

The ratio of combined sodium and potassium intake was found to have significantly more impact on risks of death from heart attack, cardiovascular disease, or other causes, than did intake of either sodium or potassium alone.

“Examining the joint effects of sodium and potassium intakes on CVD [cardiovascular disease] risk is particularly important because most of the US population consumes more sodium and less potassium daily than recommended,” observed the study authors.

[See, "What Foods Should You Eat?" discussed further below]

The new study was published in the July 11, 2011 online edition of the Archives of Internal Medicine, one of the journals of the American Medical Association.

According to background information in the article, most previous studies examining the potential link of sodium or potassium intake to risk of cardiovascular disease or death have focused only on salt or only on potassium in isolation, and have produced inconsistent results for each nutrient. Other recent studies suggesting that the ratio of sodium to potassium may be a more significant risk factor for hypertension and cardiovascular disease than intake of either nutrient alone, had been performed on relatively small samples followed for short periods.

This is the first major study to examine the relationship of the dietary ratio of salt to potassium intake with risks of death from CVD, heart attack, and all causes, in a large study population followed for a long period.

The Study Methodology

Quanhe Yang, Ph.D., from the Centers from Disease Control and Prevention, Atlanta, and colleagues analyzed data on 12,267 adults, followed for an average of 14.8 years, collected in the Third National Health and Nutrition Examination Survey Linked Mortality File. The data included dietary information, demographic characteristics, and health history, as well as information on the number of deaths, and the number of deaths from cardiovascular diseases (CVD) and ischemic heart disease (IHD), matched to the participants over the follow-up period.

The researchers analyzed the data to determine consumption of sodium and potassium, as well as the sodium-potassium ratio, and to determine the relationship between these variables and the risk of all-cause mortality as well as the risk of death from cardiovascular disease (CVD) and ischemic heart disease (IHD).

After the average follow-up period of 14.8 years, 2,270 of the participants had died; 825 of the deaths were attributed to CVD and 433 to IHD.

Findings

After adjusting for other variables, the researchers found that a higher sodium intake alone was related to increased all-cause mortality but not significantly related to increased risk of death from CVD or IHD. They found that a higher potassium intake alone was also associated with a lower mortality risk, as well as significantly associated with lower risk of death from CVD and IHD.

However, a higher sodium-potassium ratio, considering the two nutrients together, in dietary intake was found to have a more significant relationship than intake of either nutrient alone to increased risk of death from all causes as well as from CVD and IHD. In fact, the analysis showed that, after adjustments, study participants in the quartile with the highest dietary salt to potassium ratio had about 50% higher risk of death from all causes, 50% higher risk of death from cardiovascular disease (CVD), and over twice the risk of death from ischemic heart disease (IHD) as participants in the quartile with the lowest dietary salt to potassium ratio.

As detailed by the study report,

“After adjustment for calorie intake by the residual method, the observed associations were slightly strengthened (adjusted HRs: 1.50 [95% CI, 1.29-1.75], 1.52 [95% CI, 1.17-1.98], and 2.34 [95% CI, 1.53-3.58] comparing the highest quartile with the lowest quartile of sodium-potassium ratio for all-cause, CVD, and IHD mortality, respectively).”

Further, the researchers observed, “The increased risk for all-cause, CVD, or IHD mortality associated with higher sodium-potassium ratio remained largely consistent across sex, race/ethnicity, BMI, hypertension status, physical activity, and educational attainments.”

As to the relationship of dietary data to the demographics of their study population, the authors reported:

“The sodium-potassium ratio was higher among males, the younger age group, current smokers, minority groups, and those with lower educational attainment (females only), lower physical activity, higher BMI (females only), lower total cholesterol or lower HDL-C (female only), and lower systolic blood pressure.”

Explanation

As to why and how a diet high in salt and low in potassium may cause increased risk of death, the researchers wrote:

“The observed stronger and more consistent associations between the sodium-potassium ratio and mortality than between each nutrient separately and mortality may be due to complex interactions between potassium and sodium at cellular levels. High sodium levels induce increased blood pressure and hypertension by stiffening endothelial cells, thickening and narrowing resistance arteries, and blocking nitric oxide synthesis, whereas high potassium levels can counteract these effects by activating nitric oxide. The opposite biological effects of sodium and potassium may explain stronger associations of sodium-potassium ratio with CVD mortality than either sodium or potassium intake alone. Future laboratory and clinical studies could shed additional light on this observation from our study.”

Study Conclusions

“In summary,” the authors wrote, “our findings indicate that higher sodium-potassium ratio is associated with significantly increased risk of CVD and all-cause mortality in the general US population.” “Public health recommendations should emphasize simultaneous reduction in sodium intake and increase in potassium intake.”

In the study, they noted, “From a public health point of view, reduced sodium intake accompanied by increased potassium intake could achieve greater health benefits than restricting sodium alone.”

In an accompanying commentary published in the same issue of the Archives of Internal Medicine, Lynn D. Silver, M.D., M.P.H., and Thomas A. Farley, M.D., M.P.H., of the New York City Department of Health and Mental Hygiene, wrote, “This article [referring to the study] strengthens the already compelling evidence of the relationship between sodium intake and mortality.”

The authors of the Commentary went on to recommend that potassium content should be added to the Nutrition Facts panels of all food labels. They also called for the creation of a nutritional database that would help consumers and scientists better learn about the nutrient content of the U.S. food supply. “It is crucial,” they concluded, “that we understand the interplay of sodium and potassium in the diet and how to optimize intake in an increasingly processed food supply without generating harm.”

“The study’s findings are particularly troubling because U.S. adults consume an average of 3,300 milligrams of sodium per day, more than twice the current recommended limit for most Americans,” said Elena Kuklina, M.D., Ph.D., an investigator on the study and a nutritional epidemiologist with CDC’s Division for Heart Disease and Stroke Prevention.

Among the study participants, men consumed an average of 4,323 milligrams of sodium a day, while women consumed 2,918 milligrams.

“This study provides further evidence to support current public health recommendations to reduce sodium levels in processed foods, given that nearly 80 percent of people’s sodium intake comes from packaged and restaurant foods. Increasing potassium intake may have additional health benefits,” Dr. Kuklina said.

What Foods Should You Eat

The 2010 Dietary Guidelines for Americans recommends limiting intake of sodium to 1,500 milligrams per day for people 51 and older, African Americans, and those who have high blood pressure, diabetes, or chronic kidney disease. This includes about half the U.S. population. The dietary guidelines recommend that all other adults consume less than 2,300 milligrams of sodium per day, and also recommend that people eat more potassium-rich foods. They recommend consuming 4,700 milligrams of potassium per day.

Foods to avoid that are high in sodium include processed meats, such as bacon, sausage, and ham, canned soups and canned vegetables, and fast foods generally, according to MedLinePlus, a website of the National Library of Medicine, National Institutes of Health (NIH).

To lower your salt intake, it will help to eat less of these foods, less processed foods in general, and be careful about eating in restaurants. The study authors note that “it is estimated that American adults consume on average about 80% of their sodium from processed or restaurants foods.”

Foods rich in potassium include fruits such as bananas, citrus fruits, cantaloupe, prunes, and dried apricots, as well as vegetables including broccoli, peas, lima beans, tomatoes, potatoes (especially their skins), sweet potatoes, and winter squashes, according to MedinePlus.

To find the potassium content of foods, see the USDA National Nutrient Database for Standard Reference, Release 17, Potassium, K (mg) Content of Selected Foods per Common Measure.

What combination of foods will lower the salt to potassium ratio in your diet? The study authors explain,

“Because sodium is added to many foods, especially processed foods, while potassium is naturally present in most foods, a low sodium-potassium ratio may be a marker of high intake of plant foods and lower intake of processed foods. For example, cheeses, cooked meats, breads, soups, fast foods, pastries, and sugary products tend to have a higher sodium-potassium ratio, whereas fruits, vegetables, dairy products, and hot beverages tend to have a lower ratio.”

More Information

The entire study report, Sodium and Potassium Intake and Mortality Among US Adults, is available in the July 11, 2011 online edition of the Archives of Internal Medicine, one of the journals of the American Medical Association.

For more information on Salt in Food, see Nutrition.gov, a website maintained by the US Department of Agriculture.

For information on Potassium in Diet, see MedlinePlus, the website of the NIH.

See also, HelpingYouCare™’s reports on:

New Dietary Guidelines for Americans Issued by USDA and HHS

MyPlate Icon Replaces Food Pyramid

Healthy Sounding Labels Are Not Always Low In Sodium! and

Some Healthy Tips for Dining Out

See also our resource pages on Diet & Nutrition: Physical Wellness.

And, see generally, our resource pages on Wellness/ Healthy Living for Seniors & Caregivers.

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Copyright © 2011 Care-Help LLC

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