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for white men, 3,584 for African American women, and 3,612 for white women. These data complement data from national surveys and support the finding that dietary intake was well above recommended levels (Loria et al., 2001). The urinary sodium estimates are closer to the self-reported dietary estimates for men than for women in the 1988–1994 NHANES, providing additional evidence that dietary reports underestimate total sodium intake for some groups.

TRENDS IN SODIUM INTAKE: NHANES 1971–1974 THROUGH 2003–2006

This section enhances the information available on changes in sodium intake over time by adding information from NHANES 2003–2006 to existing data on time trends. Background information on the analyses and data derivation can be found in Appendix E. As described in the appendix, as is always the case with time trends data, changes in intake over time must be cautiously interpreted because of limitations in these data, particularly in older data with differences in methodologies.

Intake from Foods Over Time

While the completeness and accuracy of early NHANES data is unknown, in the four decades that sodium intake has been monitored, estimates of mean sodium intake appear to have not decreased and, in fact, have trended upward since 1971–1974 across age and gender groups. There is a less consistent upward pattern between 1988–1994 and 2003–2006 (Table 5-5).

Reasons for these changes in estimates cannot be specified with certainty. The general pattern is consistent with observed calorie increases in the population during the same period (Smiciklas-Wright et al., 2003). As discussed earlier, sodium intake is positively correlated with energy intake, so increases in energy intake are generally associated with increases in sodium. Further, different food composition databases have been used to estimate sodium intake over time, there are challenges in estimating sodium from all sources that may have changed over time, and there are likely methodological changes in assessing salt use and food composition data.

Sodium Intake Density Over Time

As described earlier, expressing sodium intake on the basis of milligrams of sodium per 1,000 calories provides another means of assessing sodium intake over time and between groups. This expression of sodium intake density can be calculated for estimates of sodium intake collected in



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