Trends in the Prevalence of Excess Dietary Sodium Intake — United States, 2003–2010

Excess sodium intake can lead to hypertension, the primary risk factor for cardiovascular disease, which is the leading cause of U.S. deaths (1). Monitoring the prevalence of excess sodium intake is essential to provide the evidence for public health interventions and to track reductions in sodium intake, yet few reports exist. Reducing population sodium intake is a national priority, and monitoring the amount of sodium consumed adjusted for energy intake (sodium density or sodium in milligrams divided by calories) has been recommended because a higher sodium intake is generally accompanied by a higher calorie intake from food (2). To describe the most recent estimates and trends in excess sodium intake, CDC analyzed 2003–2010 data from the National Health and Nutrition Examination Survey (NHANES) of 34,916 participants aged ≥1 year. During 2007–2010, the prevalence of excess sodium intake, defined as intake above the Institute of Medicine tolerable upper intake levels (1,500 mg/day at ages 1–3 years; 1,900 mg at 4–8 years; 2,200 mg at 9–13 years; and 2,300 mg at ≥14 years) (3), ranged by age group from 79.1% to 95.4%. Small declines in the prevalence of excess sodium intake occurred during 2003–2010 in children aged 1–13 years, but not in adolescents or adults. Mean sodium intake declined slightly among persons aged ≥1 year, whereas sodium density did not. Despite slight declines in some groups, the majority of the U.S. population aged ≥1 year consumes excess sodium.

NHANES is a nationally representative, multistage survey of the noninstitutionalized U.S. civilian population. Certain populations are oversampled to allow for reliable estimates within subgroups.* During NHANES 2003–2010, a total of 49,731 participants aged ≥1 year (including those currently breastfed) were screened. Participants who completed an initial in-person dietary recall in a mobile examination center were asked to complete a second 24-hour dietary recall by telephone 3–10 days later. After those with missing or incomplete dietary recall data were excluded, the final analytic sample was 34,916, for a response rate of 70.3% among those screened. The 24-hour dietary recall was collected by trained interviewers using the U.S. Department of Agriculture (USDA) automated multiple-pass method† by proxy for those aged 1–5 years, by participants with proxy assistance for those aged 6–11 years, and directly by participants aged ≥12 years. The nutrient values of sodium were assigned to foods and beverages using the USDA Food and Nutrient Database for Dietary Studies corresponding with each NHANES 2-year cycle.§ Sodium intake for each respondent on each recall day was estimated by summing the sodium consumed from each food and beverage during the previous 24 hours (excluding supplements, antacids, and salt added at the table). To evaluate trends, from 2003–2010, estimates of sodium in foods did not include salt adjustments for participants whose household used salt in cooking occasionally or less often.¶ For children consuming human milk, the sodium content was estimated and added to sodium from other foods and beverages.**

Up to two 24-hour dietary recalls were used. Data were analyzed with statistical software that fits a measurement error model.†† All estimates were based on usual sodium intake, adjusting for within person, day-to-day variability. After adjusting for the day of the week of the recall, age (years), sex, and race/ethnicity, estimates were calculated for mean usual sodium intake, sodium density, and prevalence of excess sodium intake. Jackknife replicate weights based on survey weights were used to estimate standard errors and account for the complex survey design. The differences in the prevalence of excess sodium intake were examined by z test. Using linear regression models with the usual mean intake for each 2-year phase weighted by the inverse of the variance, trends in sodium intake and sodium intake density were examined using a z test. A p-value of <0.05 was considered statistically significant. No adjustment was made for multiple testing.

During 2007–2010, the prevalence of excess usual sodium intake ranged from 79.1% for U.S. children aged 1–3 years to 95.4% for U.S. adults aged 19–50 years (Table 1). A statistically significant 2.7–4.9 percentage point decline in excess usual sodium intake occurred from 2003–2006 to 2007–2010 among children aged 1–3, 4–8, and 9–13 years, but not among adolescents or adults. Among children aged 4–8 years, statistically significant declines occurred across all sex and race/ethnicity subgroups.

Mean usual sodium intake among the U.S. population aged ≥1 year decreased slightly from 2003–2004 to 2009–2010 (3,518 mg versus 3,424 mg; p-value for trend = 0.037). The U.S. population aged ≥1 year consumed, on average, approximately 1,700 mg sodium per 1,000 kcal during 2009–2010, with no significant trend over time compared with previous investigation years (Table 2). Across age groups, mean usual sodium density did not change significantly over time, with the exception of youths aged 14–18 years, for whom sodium density increased slightly. Within age groups, mean usual sodium density slightly increased among males aged 4–8 years and females aged 14–18 years and slightly declined among non-Hispanic whites aged ≥51 years.

Reported by

Alicia Carriquiry, PhD, Iowa State Univ. Alanna J. Moshfegh, MS, Lois C. Steinfeldt, MPH, Food Surveys Research Group, Beltsville Human Nutrition Research Center, Agricultural Research Svc, US Dept of Agriculture. Mary E. Cogswell, DrPH, Fleetwood Loustalot, PhD, Zefeng Zhang, MD, PhD, Quanhe Yang, PhD, Div for Heart Disease and Stroke Prevention, National Center for Chronic Disease Prevention and Health Promotion; Niu Tian, MD, PhD, EIS Officer, CDC. Corresponding contributor: Niu Tian, vii9@cdc.gov, 770-488-5679.

Editorial Note

The findings in this report indicate that during 2007–2010, approximately eight out of 10 U.S. children aged 1–3 years and nine out of 10 U.S. residents aged ≥4 years were at potential risk for high blood pressure attributable to excess sodium intake. Although a slight decrease in the prevalence of excess usual sodium intake occurred after 2003–2006 among children aged 1–13 years, excess intake did not decrease among adolescents and adults. During 2003–2010, a slight decrease occurred in average population sodium intake, but not sodium intake per calorie. Although some variation in trends occurred among population subgroups in usual mean sodium intake and sodium density, the lack of a change in sodium consumed per calorie (approximately 1,700 mg/1,000 kcal) suggests that the small reduction in usual sodium intake might be related to declines in calorie consumption, rather than to changes in sodium density of foods.

Previous reports (4,5) included data on trends in U.S. sodium intake from the 1970s to 2003. The findings in this report update these trends, and include new data on usual excess sodium intake and sodium density. The slight declines in excess usual sodium intake among children aged 1–13 years might be partially explained by declines in energy intake among children over the same period.§§ Given an average sodium consumption of 1,700 mg/1,000 kcal/day, reducing 100 calories per day could result in a mean reduction of 170 mg of sodium per day, slightly shifting the distribution of sodium intake and lowering the percentage of those with excess intake. Among adults, the pattern of trends in sodium intake also might be explained by changes in energy intake over time. Although average energy intake declined slightly during 1999–2010 among adults aged 20–39 years, it did not change among older adults (6).

The findings in this report are subject to at least four limitations. First, NHANES data exclude military personnel and institutionalized populations such as persons who reside in long-term care or correctional facilities. Second, the response rate was 70.3%; lower response rates can result in response bias. Third, the 24-hour dietary recall underestimates mean caloric intake by an estimated 11% and sodium intake by 9%, and sodium intake excluded use of salt at the table, which accounts for nearly 5% of U.S. sodium intake (7). Finally, no adjustments for multiple comparisons were performed to determine whether differences between any pair of estimates were statistically significant.

Despite slight declines in sodium intake among some population groups, most U.S. residents aged ≥1 year consume excess sodium. Given consumption of approximately 1,700 mg of sodium per 1,000 kilocalories/day, a mean energy reduction of approximately 600 kcal/day would be required to reduce mean sodium intake by approximately 1,000 mg, to approximately 2,300 mg/day. A sodium density target of 1,000 mg/1,000 kcal was recently proposed to lower sodium intake to <2,300 mg per day (2). Given that average energy and sodium intakes have changed little over time, coupling efforts to reduce obesity with efforts to reduce the sodium content per calorie in foods might accelerate progress. Considering that 8.1% of sodium intake among U.S. children comes from school meals (8), new school food guidelines might promote progress toward achieving goals for reducing sodium consumption among children who obtain meals at school.¶¶ Other ongoing public health efforts include working with industry to gradually reduce sodium in commercially processed packaged and restaurant foods.*** Even a 400 mg reduction in mean U.S. sodium intake might save billions of health-care dollars (9).

References

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