SODIUM
Definition
Sodium is an essential nutrient required by the body to balance electrolyte levels. Its main function is to maintain water balance in the body. The most common form of sodium in the everyday diet is salt, with 40% composing of sodium and 60% composing of chloride.1 The level of sodium within the body may vary throughout the day and is dependent on a person’s dietary intake.1
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. Research has shown that people are consuming far more sodium than is required which can contribute to increased blood pressure and chronic disease such as cardiovascular disease.1
It should be noted that the most accepted and reliable assessment of sodium excretion is done using a 24 hour urine collection method. However asking participants to collect their urine over 24 hours is burdensome and likely to deter participation. Consequently, only spot urine samples were collected in the National Aboriginal and Torres Strait Islander Health Measures Survey (NATSIHMS).
WHO have recommended using a 24 hour urine collection method for establishing a baseline assessment of sodium consumption. However, there are equations and formulas that have been developed to estimate 24 hour sodium excretion from spot urine collections. 2,3,4,5,6 Note, there are no position statements on the use of these equations and formulas for the Australian or Aboriginal and Torres Strait Islander population to date, and as such estimated 24 hour sodium excretion data has not been reported in the NATSIHMS.
Population
Sodium results were obtained for persons aged 18 years and over, who agreed to participate in the NATSIHMS and who provided a urine sample. Fasting was not required for this test.
Methodology
A spot urine sample was collected from participants and urinary sodium levels were measured at the Douglass Hanly Moir (DHM) laboratory.
There is no consensus of epidemiological cut off reference values for measuring sodium excretion from spot or estimated 24 hour urine collections, and as such no cut off points have been defined in the NATSIHMS.
Further information about the analysis method and machines used to measure sodium levels are available in Excel spreadsheet format in the Downloads page of this product.
Data items
The data items and related output categories for this topic are available in Excel spreadsheet format from the Downloads page of this product.
Interpretation
Points to be considered when interpreting data for this topic include the following:
- The urinary excretion of sodium varies significantly with dietary intake and there is no method to determine expected values based on a spot urine collection. It should be noted that other studies and research may have collected and measured 24 hour urine sodium excretion.
- There are a number of different test methods to measure sodium levels and each test method may produce different results.
Comparability with other surveys
The NATSIHMS is the first ABS Aboriginal and Torres Strait Islander survey to collect biomedical information. Given it was also the first national level survey (ABS or otherwise) to collect such data for the Aboriginal and Torres Strait Islander population, no comparisons with previous surveys for this population are possible.
However, biomedical data was also collected for all Australians in the 2011-12 National Health Measures Survey (NHMS) and information about comparisons between the NHMS results and those of non-ABS surveys is available from the
Comparisons with other Australian surveys section of the
Biomedical Results for Chronic Diseases, 2011-12 publication.
ENDNOTES
1 Gibson RS, 2005,
Principles of Nutritional Assessment, 2nd ed, New York: Oxford University Press.
2 Brown IJ, Dyer AR, Chan Q, Cogswell ME, Ueshima H, Stamler J, & Elliott P, 2013, ' INTERSALT Co-Operative Research Group, 2012, 'Estimating 24-Hour Urinary Sodium Excretion From Casual Urinary Sodium Concentrations in Western Populations',
American Journal of Epidemiology, 1;177(11):1180-92.
3 Pan American Health Organization/ World Health Organization, 2010, 'Protocol for population level sodium determination in 24‐hour urine samples' ,WHO/PAHO Regional Expert Group for Cardiovascular Disease Prevention through Population]wide Dietary Salt Reduction, <
http://new.paho.org/hq/dmdocuments/2010/pahosaltprotocol.pdf>, Last accessed 08/09/2014.
4 Kawasaki T, Itoh K, Uezono K & Sasaki H, 1993, 'A simple method for estimating 24 h urinary sodium and potassium excretion from second morning voiding urine specimen in adults',
Clinical and Experimental Pharmacology and Physiology, 20(1):7–14.
5 Tanaka T, Okamura T, Miura K, Kadowaki T, Ueshima H, Nakagawa H, & Hashimoto T, 2002, 'A simple method to estimate populational 24-h urinary sodium and potassium excretion using a casual urine specimen',
Journal of Human Hypertension, 16(2):97-103 <
http://www.nature.com/jhh/journal/v16/n2/full/1001307a.html>, Last accessed 08/09/2014.
6 World Health Organization 2011,
Strategies to monitor and evaluate population sodium consumption and sources of sodium in the diet: report of a joint technical meeting convened by WHO and the Government of Canada, Report, 3-40. Geneva, Switzerland, WHO Press, <
http://whqlibdoc.who.int/publications/2011/9789241501699_eng.pdf>, Last accessed 08/09/2014.
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