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Usual Sodium Intakes Compared with Current Dietary Guidelines --- United States, 2005--2008

Morbidity and Mortality Weekly Report (MMWR)

Weekly

October 21, 2011 / 60(41);1413-1417

High sodium intake can increase blood pressure and the risk for heart disease and stroke (1,2)According to the Dietary Guidelines for Americans, 2010 (3), persons in the United States aged ≥2 years should limit daily sodium intake to <2,300 mg. Subpopulations that would benefit from further reducing sodium intake to 1,500 mg daily include 1) persons aged ≥51 years, 2) blacks, and 3) persons with hypertension, diabetes, or chronic kidney disease (3). To estimate the proportion of the U.S. population for whom the 1,500 mg recommendation applies and to assess the usual sodium intake for those persons, CDC and the National Institutes of Health used data for 2005--2008 from the National Health and Nutrition Examination Survey (NHANES). This report summarizes the results of that assessment, which determined that, although 47.6% of persons aged ≥2 years meet the criteria to limit their daily sodium intake to 1,500 mg, the usual daily sodium intake for 98.6% of those persons was >1,500 mg. Moreover, for 88.2% of the remaining U.S. population, daily sodium intake was greater than the recommended <2,300 mg. New population-based strategies and increased public health and private efforts will be needed to meet the Dietary Guidelines recommendations.

NHANES is a nationally representative, multistage survey of the U.S. non-institutionalized population.* During NHANES 2005--2008, a total of 18,823 participants aged ≥2 years were interviewed and examined. Blood pressure was measured, blood and urine were collected for testing, and a 24-hour dietary recall was administered. A second 24-hour dietary recall was administered by telephone 3--10 days later. Dietary intake for children aged 2--5 years was recalled by a proxy, for children 6--11 years by the participant assisted by a proxy, and for all others by the participant. Examination response rates were 76% during the study period. Excluded from the initial sample were pregnant women, women whose pregnancy status was not recorded (694), and participants who reported being on renal dialysis (39). Among participants aged ≥12 years, 5,508 were randomly assigned to a morning examination, fasted for 8--24 hours, and had fasting plasma glucose, glycohemoglobin (HbA1c), serum creatinine concentration, and urine albumin and creatinine measured. Excluded were persons with missing diabetes data (18) or blood pressure data (898), yielding an analytic sample of 9,468 participants, 4,268 aged 2--11 years and 5,200 aged ≥12 years.

Persons with a recommended daily sodium intake of 1,500 mg had at least one of the following characteristics: age ≥51 years, non-Hispanic black race, or hypertension, diabetes, or chronic kidney disease. Hypertension was defined as mean systolic blood pressure ≥140 mm Hg, mean diastolic blood pressure ≥90 mm Hg, or self-reported use of antihypertensive medication; diabetes as self-reported diagnosis by a health-care provider, HbA1c ≥6.5%, or fasting plasma glucose ≥126 mg/dL; and chronic kidney disease as an estimated glomerular filtration rate <60 mL/min/1.73 m2 or urinary albumin-creatinine ratio >30 mg/g (4,5).

Mean usual sodium intakes and proportions of the subpopulation with intake above 1,500 mg/day and at or above 2,300/mg day were estimated from up to two 24-hour dietary recalls using statistical software to account for day-to-day variation in intake with jackknife replicate weights based on survey sample weights to estimate standard errors and confidence intervals. For all other analyses, statistical software for complex surveys was used with the survey sample weights. For participants aged ≥12 years, survey sample weights for the fasting subsample were used. For participants aged 2--11 years, survey sample weights for the medical examination and first day diet sample were used.

Among the U.S. population aged ≥2 years in 2005--2008, an estimated 47.6% of the population met the criteria to limit sodium intake to 1,500 mg daily, according to the 2010 Dietary Guidelines (Table 1). Although this proportion differed by sex, that difference was not statistically significant after adjusting for age and race/ethnicity. The proportion of the population with a 1,500 mg daily recommendation was higher among adults (57.1%) than among children (16.2%). Among non-Hispanic blacks, non-Hispanic whites, and Mexican Americans aged ≥2 years, 100.0%, 44.1%, and 23.7%, respectively, were advised to limit their sodium intake to 1,500 mg daily.

Among persons aged ≥2 years with a 1,500 mg daily recommendation, 98.6% consumed >1,500 mg sodium on a usual daily basis, including 99.4% of those aged ≥18 years (Table 2). Among those with a sodium recommendation of <2,300 mg daily, 88.2% consumed ≥2,300 mg on a usual daily basis, including 95.0% of those aged ≥18 years.

Reported by

Catherine M. Loria, PhD, Michael E. Mussolino, PhD, Div of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, National Institutes of Health. Mary E. Cogswell, DrPH, Cathleen Gillespie, MS, Janelle P. Gunn, MPH, Darwin R. Labarthe, MD, PhD, Div for Heart Disease and Stroke Prevention; Sharon Saydah, PhD, Meda E. Pavkov, MD, Div of Diabetes Translation, National Center for Chronic Disease Prevention and Health Promotion, CDC. Corresponding contributor: Mary E. Cogswell, mcogswell@cdc.gov, 770-488-8053.

Editorial Note

The findings in this report indicate that 47.6% of the U.S. population aged ≥2 years meet the criteria of the 2010 Dietary Guidelines for persons who should limit sodium consumption to 1,500 mg daily (3). For the Dietary Guidelines, the 2005 Institute of Medicine (IOM), Dietary Reference Intakes were used to define the specific subpopulations for whom the 1,500 mg recommendation applies (2). These subpopulations tend to be more responsive than others to the blood pressure-raising effects of sodium (2,3). Additionally, IOM recommends that sodium intake not exceed the tolerable upper intake level of 1,500 mg/day for all children aged 2--3 years. The tolerable upper intake level is defined as the highest daily nutrient intake level that is likely to pose no risk of adverse health effects to nearly all persons in the general population (2). When the IOM recommendation for children aged 2--3 years is combined with the subpopulations recommended in the 2010 Dietary Guidelines to reduce intake to 1,500 mg, 50.0% (95% confidence interval [CI] = 47.6%--52.5%) of the U.S. population aged ≥2 years and 30.6% (CI = 27.8%--33.6%) of persons aged 2--17 years are advised to limit sodium intake to 1,500 mg daily.

According to IOM, a usual sodium intake of 1,500 mg daily is adequate for most adults, allowing for sweat loss among moderately active persons or those exposed to high temperatures after living in a moderate temperature environment (2)The 1,500 mg level does not apply to highly active persons (e.g., competitive athletes) or to workers exposed to high temperatures (e.g., foundry workers or firefighters) because of increased loss of sodium via sweat. However, the proportion of U.S. adults who are competitive athletes, firefighters, or foundry workers is estimated to be <0.2%.

The analysis in this report confirms that mean sodium intake in 2005--2008 exceeded guidelines for persons in all subpopulations by sex, age group, race/ethnicity, and certain chronic diseases. The results generally are consistent with previous findings that the 1,500 mg recommendation applies to the majority of U.S. adults (6) and sodium intake exceeds guidelines substantially (7).

The findings in this report are subject to at least four limitations. First, NHANES data exclude institutionalized populations such as persons who reside in long-term care or correctional facilities. Second, hypertension in children aged 2--7 years or chronic kidney disease in children aged 2--11 years were not considered because both conditions are relatively rare and their precise prevalence is unknown. Third, the assessment of sodium intake excluded table salt and sodium from dietary supplements and antacids, underestimating intake by approximately 6% (1,8). Finally, dietary data are self-reported and subject to bias because of changes in food composition not reflected in nutrient databases and because of underreporting of foods or portion sizes.

Approximately 75% of sodium consumed is added to commercial foods during processing or to restaurant foods during preparation; only about 25% occurs naturally or is added at the table or in cooking by the consumer (1,8). In 2010, IOM outlined new strategies to reduce sodium intake (1). The primary strategy is to set mandatory sodium targets for processed and restaurant foods, with supporting strategies including improved sodium content labeling, and encouraging organizations (e.g., governments or businesses) to implement procurement policies that establish sodium limits for foods they distribute (1). Recent examples of efforts to reduce populationwide sodium intake include strategies implemented by five local communities that participate in CDC's Sodium Reduction in Communities Program,§ CDC's procurement guideline for limiting sodium, which provides guidance to state and local governments on improving the food environment through nutrition standards,¶ recently released HHS standards providing guidelines that limit the sodium content of foods purchased for federal concessions and vending machines,** and U.S. Department of Agriculture (USDA) policies related to provision of low-sodium food commodities (e.g., <140 mg of sodium per serving for all canned beans and vegetables) in the National School Lunch Program.†† In addition, the U.S. Department of Health and Human Services (HHS) recently launched the Million Hearts initiative to prevent a million heart attacks and strokes in the next 5 years. As a component of this initiative, HHS and USDA formally requested comments, data, and approaches designed to promote sodium reduction.§§

Reductions in sodium intake can be achieved through population level strategies, as demonstrated by an estimated 9.5% reduction in salt intake over 7--8 years in the United Kingdom.¶¶ The reductions were associated with a government-manufacturer partnership to reduce sodium through use of voluntary maximum targets for specific processed foods.*** Similar reductions, if achieved in the United States, are estimated to save $4 billion in health-care costs per year and $32.1 billion over the lifetime of adults aged 40--85 years today (9,10). In the United States, the New York City-led National Salt Reduction Initiative set sodium benchmarks for processed and restaurant foods. To date, 28 companies have committed to meeting various benchmarks.††† In collaboration with USDA, the Food and Drug Administration, and the National Institutes of Health, CDC is monitoring sodium in the food supply, sodium intake, hypertension, and consumer readiness for programs and policies. Additional coordinated efforts involving the public and private sectors are needed to help U.S. residents follow sodium intake recommendations and to reduce medical costs and deaths from stroke and cardiovascular disease.

References

  1. Institute of Medicine. Strategies to reduce sodium intake in the United States. Washington, DC: The National Academies Press; 2010.
  2. Institute of Medicine. Dietary reference intakes for water, potassium, sodium, chloride, and sulfate. Washington DC: The National Academies Press; 2005.
  3. US Department of Health and Human Services, US Department of Agriculture. Dietary guidelines for Americans, 2010. 7th ed. Washington DC: US Department of Health and Human Services, US Department of Agriculture; 2011. Available at http://health.gov/dietaryguidelines/2010.aspExternal Web Site Icon. Accessed October 18, 2011.
  4. Levey AS, Coresh J, Balk E, et al. National Kidney Foundation practice guidelines for chronic kidney disease: evaluation, classification, and stratification. Ann Intern Med 2003;139:137--47.
  5. Levey AS, Stevens LA, Schmid CH, et al. A new equation to estimate glomerular filtration rate. Ann Intern Med 2009;150:604--12.
  6. CDC. Application of lower sodium intake recommendations to adults---United States, 1999--2006. MMWR 2009; 58: 281--3.
  7. CDC. Sodium intake among adults---United States, 2005--2006. MMWR 2010;59:746--9.
  8. Mattes RD, Donnelly D. Relative contributions of dietary sodium sources. J Am Coll Nutr 1991;10:383--93.
  9. Smith-Spangler CM, Juusola JL, Enns EA, Owens DK, Garber AM. Population strategies to decrease sodium intake and the burden of cardiovascular disease. Ann Intern Med 2010;152:481--7.
  10. Bibbins-Domingo K, Chertow GM, Coxson PG, et al. Projected effect of dietary salt reductions on future cardiovascular disease. N Engl J Med 2010;372:590--9.


* Additional information available at http://www.cdc.gov/nchs/nhanes.htm.

† Based on the estimated number of persons who were firefighters (305,500), competitive athletes (13,620), and foundry mold and coremakers (13,550) as of May 2009 (data available at http://www.bls.gov/oes/current/oes_alph.htmExternal Web Site Icon), divided by the estimated U.S Census Population as of July 1, 2009 (307,006,550).

§ Additional information available at http://www.cdc.gov/dhdsp/programs/sodium_reduction.htm.

¶ Additional information available at http://www.cdc.gov/salt/pdfs/dhdsp_procurement_guide.pdf Adobe PDF file.

** Additional information available at http://www.gsa.gov/portal/content/104429External Web Site Icon.

†† Additional information available at http://www.fns.usda.gov/fdd/news/schupdates1010.pdf Adobe PDF fileExternal Web Site Icon.

§§ Additional information available at http://www.fda.gov/food/newsevents/constituentupdates/ucm271915.htmExternal Web Site Icon.

¶¶ Additional information available at http://www.food.gov.uk/multimedia/pdfs/08sodiumreport.pdf Adobe PDF fileExternal Web Site Icon.

*** Additional information available at http://www.food.gov.uk/multimedia/pdfs/consultation/iarevsaltredtargets.pdf Adobe PDF fileExternal Web Site Icon.

††† Additional information available at http://www.nyc.gov/html/doh/html/cardio/cardio-salt-initiative.shtmlExternal Web Site Icon.


What is already known on this topic?

Dietary Guidelines for Americans, 2010 recommends that persons in the United States aged ≥2 years limit sodium intake to <2,300 mg daily and that 1) persons aged ≥51 years, 2) blacks, and 3) persons with hypertension, diabetes, or chronic kidney disease should limit sodium intake to 1,500 mg daily to reduce their risk for hypertension, heart disease, and stroke.

What is added by this report?

According to the 2005--2008 National Health and Nutrition Examination Survey, the recommendations to restrict daily sodium intake to 1,500 mg applied to 47.6% of persons in the United States aged >2 years. However, 98.5% of those persons consumed more than the recommended amount of sodium on a usual daily basis, and among those with a sodium recommendation of <2,300 mg daily, 88.2% consumed more than the recommended amount on a usual daily basis.

What are the implications for public health practice?

Because usual sodium intake for nearly all U.S. residents exceeds the 2010 Dietary Guidelines, increased efforts involving the public and private sectors (e.g., voluntary reductions in processed and restaurant food) will be needed to help the public follow sodium intake recommendations and reduce medical costs and deaths associated with stroke and cardiovascular disease.

from CDC