Surveillance

Establish mean daily sodium intake

Mean dietary sodium provides information on intake relative to the WHO recommended maximum adult intake of 2,000 mg of sodium (5 g salt) per day and sets the baseline for measuring future progress. Assess sodium intake through a nationally representative, adequately powered survey.

Several different methodologies can be used for measuring mean daily sodium intake. While more expensive and labor-intensive than other methods, the most accurate method is to collect complete 24-hour urine samples and analyze them for sodium and creatinine. (Although single 24-hour urine collections are not a reliable indicator of an individual’s usual sodium intake, the method is accurate on a population basis if the urine collections are complete.).

Measurement of sodium and creatinine using spot urine samples can be used to estimate average population 24-hour sodium intake. This method is used as part of the WHO STEPS survey and is less expensive and technically much easier than 24-hour urine collection. While it appears to be an acceptable way to assess the average population sodium intake at a single time point, using spot urine samples to assess change in average population sodium intake over time is considered to be less reliable (though research is still ongoing). Spot urine samples also underestimate the distribution of sodium intake. Ideally, if using spot urine samples, there should be a validation sub-sample where 24-hour urine samples are collected.

Dietary recall surveys (e.g., one or more 24-hour recalls) are another option for measuring sodium intake. Validity is highly dependent on the recall ability of the respondents, completeness and accuracy of the food database used to support the survey, and it is an unreliable method for assessing sodium added during cooking or at the table. While sodium intake can be significantly underestimated using this method (especially where food databases are less reliable or large proportions of sodium are added at home, in cooking or at the table), one advantage of the dietary recall survey is that it also assesses the dietary sources of sodium and provides information that is valuable for other, complementary nutrition initiatives. In some cases, surveys also quantified sodium intake using food weighing methods (Du 2014).

Establish the main sources of dietary sodium

Dietary sodium is typically consumed from three distinct sources: sodium added to packaged food during manufacturing, sodium added to food consumed outside the home (e.g., restaurants, street food vendors, cafeterias/canteens), and discretionary sources (sodium added in the home, either during cooking or while eating). The main dietary sources of sodium are usually established by dietary recall surveys or food frequency questionnaires (FFQ). The validity of the survey results is highly dependent on the recall ability of the respondents and the accuracy and completeness of the sodium content of the foods in the database used to support the survey. It is important to have data for the sodium content in targeted primary sources of sodium in order to track reductions over time (in addition to broader data on population sodium intake). Developing and updating a database to track the sodium content of foods is important for tracking changes that may occur during the intervention. If the intervention is successful, there may also be changes in the main dietary sources of sodium.

If it is not possible to pinpoint the main dietary sources of sodium, understanding the main components of the diet (regardless of the sodium content) can help plan and prioritize interventions.

Identify the sodium content in key packaged food categories

Many of the well-defined, evidenced-based policies to reduce sodium intake focus on packaged foods. A crucial starting point for these policies is to establish a database including key categories of packaged foods and their sodium levels. The easiest way to build this type of database is to use the sodium content from nutrition labels. Appendix 3 provides guidance on developing a food database via visits to food retail stores. In some settings, most of the data can be collected efficiently from online sources, and commercial groups may sell data on the nutrient content of packaged foods. Various technologies have been developed to assist collection of packaged food label data, such as applications that allow for simpler in-person data collection (e.g., FLIP, FoodSwitch), web-scraping techniques (e.g., foodDB), or crowd-sourcing (e.g., FoodSwitch).

While the Food and Agriculture Organization and WHO’s Codex Alimentarius (“Codex”) recommends that sodium be required on packaged food nutrient declarations, many countries still do not require it. See Section 10A for specific recommendations on mandatory nutrient declaration labeling. In addition to collecting label data, it may be necessary to measure the sodium level of selected foods for monitoring; in some countries, labeled nutrient content can be inaccurate even if labeling is required. Government food authorities can also create a national database of packaged foods by making it mandatory for food industry to submit nutritional content (including sodium) of packaged foods when applying for product registration.

Establish the levels of iodine fortification and intake

Once a major global public health concern, iodine deficiency has been largely overcome in many countries by iodizing salt. The levels of iodine added to salt should be based on sodium intake in the population; more iodine can be added as sodium intake falls, allowing for optimum intake of both nutrients. Iodine fortification and sodium reduction programs are thus mutually compatible and should be coordinated wherever possible in terms of both advocacy and communication (to policymakers, the food industry and the public) and to program surveillance and evaluation.

Iodine intake can be monitored along with sodium, with particular attention to the populations most vulnerable to iodine deficiency: children and pregnant women.Iodine is typically assessed using spot urine samples but, like sodium, can be more accurately measured using complete 24-hour urine samples.

Assess public knowledge, attitudes and practices (KAP)

Assessing the public’s knowledge, attitudes and practices (KAP) relating to dietary sodium can help in the design and monitoring of behavior change and education programs and provides a baseline of the public’s receptivity to and support of potential policy interventions. The result of repeated KAP surveys can be used to track the effectiveness of mass media campaigns, educational interventions and policy changes. However, monitoring changes in practice through KAP indicators cannot replace a quantitative assessment of sodium intake; many projects have seen changes in KAP survey indicators without changes to sodium intake.

KAP surveys can also be designed to assess the food industry’s knowledge, willingness and intention to change, the support or challenges from the health and scientific sector and from policymakers.

Innovative methods: household budget surveys to assess sodium intake and sources

A small number of countries (Brazil, Poland, Slovenia, and Costa Rica) have used Household Budget Surveys (HBS) to estimate average sodium consumption and major dietary sources of sodium. The method is rapid and inexpensive, with most countries collecting data through HBS every 4-5 years. There is inadequate research at this time to assess the generalizability or reliability of using this approach.