The results in Figure 2-13 suggest that intake increased between 1971–1974 and 1988–1994 and then plateaued between 1988–1994 and 2005–2006. Whether the early increases are real or due to methodological artifacts is uncertain. There were improvements in interview methodologies during that time that were associated with more complete reporting of intake (Loria et al., 2001). However, even with the caveat that intake by individuals tends to be underestimated and caution as to possible methodological sources of underestimation in the early surveys, the mean intakes, except for adult women in the first two survey periods, are all in excess of Dietary Guidelines for Americans recommendations.
One way of crudely evaluating whether or not underreporting biases have influenced time trends in estimates of sodium intake is to evaluate whether the differences in sodium intake over time and among subgroups are negated or minimized when the results are expressed as sodium densities. Using the same database as in Figure 2-13, Figure 2-14 provides data on the sodium densities for the same surveys.