Sodium
Definition
Sodium is an essential nutrient required by the body to regulate the body’s fluids. Its main function is to maintain water balance in the body. The level of sodium within the body may vary throughout the day and is dependent on a person’s dietary intake. The most common form of sodium in the everyday diet is salt which may be added during manufacturing, processing, cooking and preparing foods and drinks, and as salt at the table. Sodium may also be present naturally in foods, in food additives, dietary supplements and/or medicines (WHO 2012; NHMRC 2017).
There is strong evidence that there is a relationship between excessive sodium intake and blood pressure. Hypertension (high blood pressure) is a significant risk factor for cardiovascular disease. Research has shown that most people are consuming more sodium than is required (WHO 2012; NHMRC 2017).
A biomedical measure of sodium intakes is useful in addition to estimating sodium intakes from the diet. Estimated total sodium intakes from food and dietary supplements can be inaccurate as salt used in cooking and preparation of food or added at the table cannot be measured and food composition tables may not reflect the sodium content of all foods available in the food supply, particularly when reformulation programs are ongoing (McLean 2014; DHAC 2023).
The 2013 National Health and Medical Research Council (NHMRC) Nutrient Reference Values for sodium for Australia and New Zealand populations were expressed as Adequate Intakes and Upper Levels of Intake (UL) (NHMRC 2013).
In 2017, following a review of nutrient reference values, a suggested dietary target (SDT) was set for sodium for adults, which is defined as the daily average intake of a nutrient that may help in the prevention of chronic disease (in this case ‘average’ refers to the median intake of the population; NHMRC 2017). The SDT for sodium for adults is <2000 mg/day. The SDT is in line with the World Health Organization (WHO) guideline sodium intake for adults of <2000 mg/day (equivalent to <5 g salt per day; WHO 2012, 2023b). In the 2017 review, the UL for adults was set as ‘not determined’ due to lack of evidence (NHMRC 2017).
Reducing sodium/salt intakes by 30% is one of the WHO’s nine key targets for reducing noncommunicable diseases (WHO 2013). Monitoring of population sodium intake should accompany public health initiatives aimed at sodium reduction in the diet (WHO,] 2023a, b).
In Australia, the Department of Health and Aged Care (DHAC) works with the food industry through a voluntary Partnership Reformulation Program to reduce the amount of saturated fat, sodium and sugar in a range of manufactured and processed food and drinks (DHAC 2023).
Laboratory test information, including analysis methods and machines used to measure sodium, is available from the Downloads page.
Methodology
Sodium results were obtained for persons aged 5 years and over who provided a urine sample. Fasting was not required for this test.
Urinary sodium levels were measured at the Douglass Hanly Moir Pathology (DHM) laboratory using an integrated chip technology method. The sodium test measures the total amount of sodium in the urine that has been excreted from the body at the time of the test (spot test), expressed as mmol/L.
There is no consensus of epidemiological cut-off reference values for reporting sodium excretion for spot urine collections. As such no cut-off points have been defined.
The WHO recommends using a 24-hour urine collection method for establishing a baseline assessment of sodium consumption (WHO/PANO 2011; WHO SEARO 2021). A 24-hour urinary collection is widely considered to be the most accurate method of measuring sodium intakes as over 90% ingested sodium is excreted in urine within a 24-hour period. The amount of sodium in the urine reflects what was eaten at the last meal and how much fluid an individual has drunk in the last 24 hours (McLean 2014). In the IHMHS, a spot urine sample was used to test sodium content as it was not practical to collect urine samples from all study participants over a 24-hour period due to the high respondent burden and other method limitations (McLean 2014). Although not ideal for estimating sodium intakes, spot urine sodium data can be used for the purposes of monitoring changes in population sodium intakes over time and has been used in other national biomedical surveys (McLean 2014; PHE 2020).
The 24-hour urine sodium excretion amount may be estimated from spot urine data but there are no position statements on the use of the available equations and formulas to estimate 24-hour sodium excretion from spot urine data for the Australian population to date. Several equations and formulas have been developed for this purpose elsewhere (WHO/PAHO 2011; McLean et al. 2018; He et al. 2019; Huang et al. 2020; WHO SEARO 2021).
Sodium data is not currently included in ABS publications. However, sodium results are available in DataLab microdata products.
Interpretation
Points to be considered when interpreting data for this topic include the following:
- Urinary sodium results do not indicate a specific diagnosis without consultation with a health professional.
- There are several different methods to measure urinary sodium levels, and each test method or collection method may produce different results. The data from this topic should therefore be used with caution when comparing sodium results from other studies using a different test method.
- The urinary excretion of sodium varies significantly with dietary intake and there is no consensus on methods to determine expected 24-hour values based on a spot urine sodium data. As such estimated 24-hour sodium excretion data has not been reported.
Comparison to other sodium biomarker data
This is the second time the ABS has collected information on sodium levels. Urinary sodium data was previously collected in the NHMS 2011–12 and the NATSIHMS 2012–13. For information on time series comparability, see Comparing biomedical collections over time.
Sodium data has been collected in other non-ABS surveys. However, caution must be taken when interpreting results due to the differences in scope, assay and the instrument used, and any thresholds applied in the final analysis.
References
Department of Health and Aged Care (DHAC) (2023), Partnership Reformulation Program, DHAC website, accessed 20/02/2025.
He FJ, Ma Y, Campbell NRC, MacGregor GA, Cogswell ME, Cook NR (2019), Formulas to Estimate Dietary Sodium Intake From Spot Urine Alter Sodium-Mortality Relationship, Hypertension, 74(3):572-580, accessed 20/02/2025.
Huang L, Trieu K, Yoshimura S, Neal B, Woodward M, Campbell NRC, Li Q, Lackland DT, Leung AA, Anderson CAM, MacGregor GA, He FJ. 2020. Effect of dose and duration of reduction in dietary sodium on blood pressure levels: systematic review and meta-analysis of randomised trials, BMJ, 368:m315, accessed 20/02/2025.
McLean RM (2014), Measuring Population Sodium Intake: A Review of Methods, Nutrients, 6(11):4651-4662, accessed 20/02/2025.
McLean RM, Williams SM, Te Morenga LA, Man JI (2018), Spot urine and 24-h diet recall estimates of dietary sodium intake from the 2008/09 New Zealand Adult Nutrition Survey: a comparison, European Journal of Clinical Nutrition, 72:1120-1127, accessed 20/02/2025.
National Health and Medical Research Council (NHMRC) (2013), Nutrient Reference Values for Australia and New Zealand: Including Recommended Dietary Intakes, NHMRC, accessed 20/02/2025.
National Health and Medical Research Council (NHMRC) (2017), ‘Sodium’ Nutrient Reference Values for Australia and New Zealand, Eat for Health website, accessed 20/02/2025.
Public Health England (PHE) (2020), National Diet and Nutrition Survey: Assessment of salt intake from urinary sodium in adults (aged 19 to 64 years) in England, 2018 to 2019, National Diet and Nutrition Survey, GOV UK, accessed 20/02/2025.
World Health Organization (WHO) (2012), Guideline: sodium intake for adults and children, WHO, accessed 20/02/2025.
World Health Organization (WHO) (2013), NCD Global Monitoring Framework, WHO, accessed 20/02/2025.
World Health Organization (WHO) (2023b), Sodium reduction, WHO website, accessed 20/02/2025.
World Health Organization (WHO) (2023a), WHO Global Report on sodium intake, WHO, accessed 20/02/2025.
World Health Organization South-East Asia Regional Office (WHO SEARO) (2021), Measurement of population sodium intakes, World Action on Salt, Sugar and Health, accessed 20/02/2025.
World Health Organization (WHO)/Pan American Health Organization (PAHO) Regional Expert Group for Cardiovascular Disease Prevention through Population-wide Dietary Salt Reduction (2011), Protocol for Population Level Sodium Determination in 24-Hour Urine Samples, PAHO, accessed 20/02/2025.