VITAMIN D

Definition

Vitamin D is essential for the body to absorb calcium effectively, which is important for bone health and muscle function, and for preventing conditions such as osteoporosis. The main source of vitamin D is exposure to sunlight, although small amounts can be obtained through some foods, such as eggs, fatty fish and fortified margarine and milk.^1,2

The main consequence of severe vitamin D deficiency is rickets in children and osteopenia (fragile bones) in older people.² There is some evidence to suggest that low vitamin D levels could also be a risk factor for other chronic conditions, such as diabetes and heart disease, but more research is needed to better understand these links. ^1,3

The vitamin D test measures the total amount of vitamin D obtained from both food and sunlight, circulating in the blood, at the time of the test.²

Population

Vitamin D results were obtained for persons aged 18 years and over, who agreed to participate in the NATSIHMS and who provided a blood sample. Fasting was not required for this test.

Methodology

A blood sample was collected from participants and vitamin D levels were measured at the Douglass Hanly Moir (DHM) laboratory.

Ranged cut off points for adequate and deficient levels of vitamin D were reported in the NATSIHMS. These cut offs are based on the current position statement on Vitamin D and health in adults in Australia and New Zealand, published in the Medical Journal of Australia (MJA).¹ Note that in most of the ABS output, the moderate and severe vitamin D deficiency cut offs have been collapsed due to small numbers.

In the NATSIHMS, the following definitions were used:

• Adequate levels: ≥50 nmol/L
• Mild deficiency: 30 – 49 nmol/L
• Moderate deficiency: 13* – 29 nmol/L
• Severe deficiency: <13* nmol/L
• Total deficiency: <50 nmol/L#

*Note that the cut-off recommended in the position statement is <12.5 nmol/L, but the NATSIHMS is unable to output against this cut-off as the Vitamin D data is only available in whole numbers.
# Note that the position statement states that levels may need to be 10 to 20 nmol/L higher at the end of summer, to allow for seasonal decrease.

Further information about the analysis method and machines used to measure vitamin D 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:

• Vitamin D test results do not confirm a specific diagnosis without consultation with a health professional.
• There are a number of different test methods to measure vitamin D levels and each test method may produce different results. Note that all NATSIHMS blood samples, which produced vitamin D test results, were analysed by Liquid Chromatography-tandem Mass Spectrometry (LC-MS/MS). The data from this topic should therefore be used with caution when comparing vitamin D results from other studies using a different test method.

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.

The Australian Aboriginal and Torres Strait Islander Health Survey (AATSIHS) 2012-13, which is part of the Australian Health Survey 2011-13, is currently one of eight national surveys participating in the international Vitamin D Standardization Program (VSDP), which aims to standardise the measurement of vitamin D across all laboratories to enable the transfer of findings to patient care and public health activities.⁵ For more information on the VDSP and it's progress, see details on the National Institutes of Health website.

ENDNOTES

1 Nowson CA, McGrath JJ, Ebeling PR, Haikerwal A, Daly RM, Sanders KM Seibel MJ & Mason RS, 2012, Vitamin D and health in adults in Australia and New Zealand: a position statement. Medical Journal of Australia, 196:686-687, <https://www.mja.com.au/journal/2012/196/11/vitamin-d-and-health-adults-australia-and-new-zealand-position-statement>, Last accessed 08/19/2014.
2 Gibson RS, 2005, Principles of Nutritional Assessment, 2nd ed, New York: Oxford University Press.
3 The Royal College of Pathologists of Australasia, May 2013, Position statement; Use and Interpretation of Vitamin D testing, <http://www.aims.org.au/documents/item/347>, Last accessed 08/19/2014.
4 Matsuoka LY, Wortsman J, Haddad JG, Kolm P, Hollis BW, 1991, Racial pigmentation and the cutaneous synthesis of vitamin D, Archives of Deteratology, <http://www.ncbi.nlm.nih.gov/pubmed/1848745?dopt=Abstract>, Last accessed 08/19/2014.
5 National Institutes of Health Office of Dietary Supplements, 2013,Vitamin D Standardization Program (VDSP) Symposium: Tools to Improve Laboratory Measurement, U.S. Department of Health and Human Services, <http://ods.od.nih.gov/News/VDSPSymposium_2013.aspx>, Last accessed 08/19/2014.

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