The average American diet appears to have the ratio the wrong way round: high sodium and low potassium, which increases risk of death, instead of low sodium and higher potassium, which reduces it, according to a new study led by the US Centers for Disease Control and Prevention (CDC) published online in the Archives of Internal Medicine this week.
Researchers from the CDC, Emory University and Harvard University, found that:
- A diet high in sodium increases risk of death from all causes,
- Increasing potassium intake reduces risk of death from all causes, and
- A high sodium to potassium ratio (too much sodium, not enough potassium) increases risk of death from all causes and cardiovascular disease by nearly 50%, and more than doubles the risk of death from heart attacks.
The researchers analyzed data from the Third National Health and Nutrition Examination Survey (NHANES), a nationally representative survey that assesses the health and diet of the US population. Data on diet and health came from interviews where participants are asked to recall what they consumed in the previous 24 hours, and data from physical exams and lab tests helped to assess medical status.
This study used the NHANES Linked Mortality File covering data from 1988 to 2006 on 12,267 US adults and the researchers investigated links between dietary sodium and potassium intake and all-cause, cardiovascular, and ischemic heart diseases mortality.
The results showed that:
- Over a mean follow-up period of 14.8 years, there were 2,270 deaths, including 825 from cardiovascular causes and 443 from ischemic heart diseases.
- After adjusting for the usual confounders, higher sodium intake was linked to an increased risk of death from all causes (Hazard Ratio HR = 1.20; 95% Confidence Interval CI = 1.03 to 1.41; per 1000 mg per day).
- But higher potassium intake was linked to a lower risk of death (HR=0.80; 95% CI=0.67-0.94; per 1000 mg/d).
- Ranking the participants according to the ratio of sodium to potassium intake such that the highest ratio (high sodium, low potassium) was at the top, and comparing the HRs of the top 25% (upper quartile) with the bottom 25% (lower quartile), the adjusted HRs were 1.46 for all-cause mortality (95% CI=1.27-1.67), 1.46 for cardiovascular mortality (95% CI=1.11-1.92), and 2.15 for ischemic heart diseases mortality (95% CI=1.48-3.12).
- Distinguishing the results by gender, race/ethnicity, body mass index (BMI), education levels, exercise and whether participants had high blood pressure or not did not appear to make any difference to these findings.
Study investigator Dr Elena Kuklina, who is a nutritional epidemiologist in the Division for Heart Disease and Stroke Prevention at the CDC, told the press the findings are disturbing because on average, the adult American consumes about 3,300 mg of sodium a day, which is more than double the recommended limit for most Americans.
The current advice (2010 Dietary Guidelines for Americans) is that adults in general should consume no more than 2,300 mg of sodium a day, but adults over 50 years of age, African Americans, and people with high blood pressure, diabetes or chronic kidney disease (about half the population of the US), should limit themselves to no more than 1,500 mg a day.
The Guidelines also advise people to consume 4,700 mg of potassium a day and to choose more foods containing potassium.
“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,” said Kurklina.
Most of the sodium the average American consumes gets into the diet as sodium chloride or salt that is added to processed and restaurant foods as well as via the salt shaker at the table or in the kitchen.
Potassium on the other hand, is naturally present in fresh foods.
Fast foods, pastries, cheese, processed meats, breads and soups, tend to have less potassium than sodium. But milk, yogurt and fruits and vegetables have more potassium and less sodium.
Leafy greens, including spinach, collards such as cabbage and broccoli, soft fruits such as grapes and blackberries, citrus fruits such as oranges and grapefruit, and vegetables like carrots and potatoes, are all rich sources of potassium.
“Sodium and Potassium Intake and Mortality Among US Adults: Prospective Data From the Third National Health and Nutrition Examination Survey.”
Quanhe Yang, Tiebin Liu, Elena V. Kuklina, W. Dana Flanders, and others.
Arch Intern Med. 2011;171(13):1183-1191.
Published online 11 July 2011; doi:10.1001/archinternmed.2011.257
Written by: Catharine Paddock, PhD