Sodium/Potassium Ratio Important for Health

July 11, 2011 (Atlanta, Georgia) — People with the highest ratio of sodium to potassium in their diet had a significantly increased risk of death from cardiovascular disease compared with those who had the lowest ratio of sodium to potassium intake over a 15-year follow-up, a new study has shown [1]. Dr Quanhe Yang (Centers for Disease Control and Prevention, Atlanta, GA) and colleagues report their findings in the July 11, 2011 issue of the Archives of Internal Medicine.

"This is the first large, nationwide study where we followed a pretty big cohort of people and looked at sodium and potassium at the same time," coauthor Dr Elena V Kuklina (Centers for Disease Control and Prevention) told heartwire .

"The major implications of our findings are that a diet balanced in both micronutrients is important. People should try to reduce sodium in particular by consuming less processed food, but also they should increase potassium intake, and this is easily done by eating more fruit and vegetables and dairy products, which are a good source of potassium and low in sodium. This is nothing new; a healthy diet is good for your health."

Kuklina stresses that people must understand the massive impact that processing has on foods: for example, 100 g of unprocessed pork contains 61 mg of sodium and 340 mg of potassium, she notes, but turning this into ham alters that ratio significantly, to yield a whopping 921 mg of sodium and, to boot, reduces the potassium content to 240 mg.

In an accompanying editorial [2], Drs Lynn D Silver and Thomas A Farley (New York City Department of Health and Mental Hygiene, NY) agree: "It is crucial 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."

Sodium/Potassium Ratio of <1 Is Protective

Yang et al examined the usual intakes of sodium and potassium as well as their ratio in relation to risk of all-cause and CVD mortality in the Third National Health and Nutrition Examination Survey (NHANES III), a prospective cohort study of 12 267 US adults.

Kuklina said the methodology employed was "more rigorous" than in previous studies because as well as assessing diet for participants once, based on one-day recall, the investigators did this on a second, separate day, for a subsample of around 1000 people and extrapolated these findings to obtain "more precise dietary intake for the rest of the cohort."

During a mean follow-up of 14.8 years, there were a total of 2270 deaths, including 825 cardiovascular deaths and 443 ischemic heart-disease deaths. After multivariable adjustment, higher sodium intake was associated with increased all-cause mortality (HR 1.20 per 1000 mg/day), whereas higher potassium intake was associated with lower mortality risk (HR 0.80 per 1000 mg/day).

For sodium-potassium ratio, the adjusted hazard ratios comparing the highest quartile with the lowest quartile were 1.46 for all-cause mortality, 1.46 for CVD mortality, and 2.15 for ischemic heart disease (IHD) mortality.

Some of the findings "are not new," says Kuklina. "We know for sure the relationship between sodium and hypertension, although there is a little bit more inconsistency when it comes to sodium and CVD mortality. And we know that higher potassium is protective against hypertension, but much less is known about potassium intake and cardiovascular disease and mortality."

We found that potassium does matter.

The results show that sodium/potassium ratio of <1 is protective, she says: "We found that potassium does matter."

One simple way of boosting potassium, she notes, is to replace regular snacks with fruit. For example, a doughnut contains 210 mg of sodium and 120 mg of potassium. "Swap this for an orange, and you will have just 1.6 mg of sodium and 150 mg of potassium."

More Trials Needed on Interactive Effects of Sodium and Potassium

In their editorial, Silver and Farley discuss the well-known barriers to implementing the dietary change that will be necessary to lower sodium and increase potassium intake. They applaud efforts to reduce sodium artificially added to food during processing and say public policies to increase dietary intake of potassium--for example, by making fruits and vegetables cheaper--should be promoted.

In addition, adequately powered longer-term trials of the interactive effects of dietary sodium and potassium--including further study of the use of potassium-rich, reduced-salt substitutes--with clinically relevant outcomes, including mortality, are needed, they conclude.

Neither the authors nor the editorialists have any conflicts of interest.