51–70 years, and > 70 years is 4,808, 3,734, 3,179, and 2,589 mg/d, respectively.
Data from NHANES 2003–2006 on all sources of sodium included salt added at the table. On average, 5 percent of total sodium (178 mg of 3,614 mg) is estimated to be from salt added at the table (see Table 5-1 and Appendix F, Table F-1). The proportion of total sodium contributed by table salt is similar across age and gender groups. These data are consistent with those of Mattes and Donnelly (1991) who reported a similar estimate in 1991 using a sample of 62 adults.
Approximately 1 percent (0.7 percent or 27 of 3,614 mg) of sodium intake is contributed by water, as shown in Table 5-1 and Appendix F (Table F-1). These data agree with the earlier, small study of Mattes and Donnelly (1991). Factors contributing to the sodium content of natural water include the evaporation of ocean spray particles that turn into raindrops, contamination of freshwater aquifers with seawater, road salt that is carried into water supplies by melting snow or rainwater, and the use of home water softeners (Korch, 1986). The sodium content of tap water varies by geographic location and even by source within the same locality (Azoulay, 2001). In the United States, sodium has been found to range from 0.1 to 39.1 mg/100 g in water supplies (Pehrsson et al., 2008), with an average 50 mg/L in tap water (Hoffman, 1988) and less than 10 mg/L in bottled water (according to the USDA National Nutrient Database for Standard Reference11).
Use of water softeners also contributes sodium to water (Bradshaw and Powell, 2002). Water softeners convert hard water characterized by a high calcium and magnesium content into softer water by an ion-exchange process that swaps sodium for these minerals. The amount of sodium added by a water softener is a function of the hardness of the water; the harder the water, the more sodium is needed to soften it. One study (Korch, 1986) found that the amount of sodium added by a water softener ranges up to 100 mg/L. Another study (Yarows et al., 1997) examined sodium concentrations in samples of softened water compared to sodium concentrations
Available online: http://www.nal.usda.gov/fnic/foodcomp/search/ (accessed November 11, 2009).