Assessment of the Proportion of Sodium Intake From a Variety of Sources - Salt Sources Study

The Centers for Disease Control and Prevention conducted an observational cross-sectional study to obtain information about the amount of sodium consumed from various sources (including sodium from processed and restaurant foods, sodium inherent in foods, and salt added at the table and during cooking) and to examine variability across population subgroups. Data collection will include an observational component as well as a sub-study designed to refine the accuracy of estimates of total sodium intake and discretionary sodium intake.

Information was collected in three distinct geographic regions: 1) Minneapolis/St. Paul, Minnesota, 2) Birmingham, Alabama, and 3) Palo Alto, California. Over a two-year period, a study center in each location recruited 150 participants (total N=450). Overall, an approximately equal number of adults ages 18-74 years by approximately 10-year age groups in each sex-race group, including whites, blacks, Hispanics, and Asians. A sub-study was conducted among a subgroup of 150 of these participants (50 per site). University of Minnesota serves as a study coordinating center.

After informed consent and completing a screening process, each participant completed a personal questionnaire, a tap water questionnaire, four 24-hour dietary recalls, and four qualitative food records. In addition, height and weight information on each participant were collected, and each participant collected duplicate portions of their cooking/table salt. A few participants at each site also provided water samples analyzed to produce estimates of the amount of sodium in private sources of tap water.

The Salt Sources Study also included a sub-study to help determine the accuracy of estimates of total sodium intake and discretionary salt intake. About 25 participants at each site used a Study Salt for 11 days instead of their own household salt, provide additional information based on four 24-hour urine collections, four follow-up urine collection questionnaires, and three follow-up questionnaires on Study Salt use. The Study Salt has the same amount of sodium and contains a very small amount of lithium, a metal found in trace amounts in all plants and animals and excreted in urine. Participants are instructed to use the study salt as they would their salt at home and to collect duplicate samples of the amount used at the table and during home cooking. The amount of lithium excreted in the 24-hour urine collection is measured to assess the amount of sodium consumed from discretionary salt use (salt used at the table and during home cooking).

Results from the Salt Sources Study will be used to inform public health strategies to reduce sodium intake, determine if substantial variability in sources of sodium intake exists by social and demographic subgroups, and better inform estimates of salt added at the table used in Healthy People 2020 objectives related to sodium reduction.