Vitamin D deficiency is recognised as a public health problem globally, and a high prevalence of deficiency has previously been reported in Australia. This study details the prevalence of vitamin D deficiency in a nationally representative sample of Australian adults aged ≥25 years, using an internationally standardised method to measure serum 25-hydroxyvitamin D (25(OH)D) concentrations and identifies demographic and lifestyle factors associated with vitamin D deficiency. We used data from the 2011–2013 Australian Health Survey (n 5034 with complete information on potential predictors and serum 25(OH)D concentrations). Serum 25(OH)D concentrations were measured by a liquid chromatography-tandem MS that is certified to the reference measurement procedures developed by the National Institute of Standards and Technology, Ghent University and the US Centers for Disease Control and Prevention. Vitamin D deficiency and insufficiency were defined as serum 25(OH)D concentrations <50 nmol/l and 50 to <75 nmol/l, respectively. Overall, 20 % of participants (19 % men; 21 % women) were classified as vitamin D deficient, with a further 43 % classified as insufficient (45 % men; 42 % women). Independent predictors of vitamin D deficiency included being born in a country other than Australia or the main English-speaking countries, residing in southern (higher latitude) states of Australia, being assessed during winter or spring, being obese, smoking (women only), having low physical activity levels and not taking vitamin D or Ca supplements. Given our increasingly indoor lifestyles, there is a need to develop and promote strategies to maintain adequate vitamin D status through safe sun exposure and dietary approaches.

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Vitamin D has previously been quantified in some plants and algae, particularly in leaves of the Solanaceae family. We measured the vitamin D content of Australian native food plants and Australian-grown edible seaweed. Using liquid chromatography with triple quadrupole mass spectrometry, 13 samples (including leaf, fruit, and seed) were analyzed in duplicate for vitamin D2, vitamin D3, 25-hydroxyvitamin D2, and 25-hydroxyvitamin D3. Five samples contained vitamin D2: raw wattleseed (Acacia victoriae) (0.03 µg/100 g dry weight (DW)); fresh and dried lemon myrtle (Backhousia citriodora) leaves (0.03 and 0.24 µg/100 g DW, respectively); and dried leaves and berries of Tasmanian mountain pepper (Tasmannia lanceolata) (0.67 and 0.05 µg/100 g DW, respectively). Fresh kombu (Lessonia corrugata) contained vitamin D3 (0.01 µg/100 g DW). Detected amounts were low; however, it is possible that exposure to ultraviolet radiation may increase the vitamin D content of plants and algae if vitamin D precursors are present.

Background: Nearly one in four Australian adults is vitamin D deficient (serum 25-hydroxyvitamin D concentrations [25(OH)D] < 50 nmol L -1 ) and current vitamin D intakes in the Australian population are unknown. Internationally, vitamin D intakes are commonly below recommendations, although estimates generally rely on food composition data that do not include 25(OH)D. We aimed to estimate usual vitamin D intakes in the Australian population. Methods: Nationally representative food consumption data were collected for Australians aged ≥ 2 years (n = 12,153) as part of the cross-sectional 2011-2013 Australian Health Survey (AHS). New analytical vitamin D food composition data for vitamin D 3 , 25(OH)D 3 , vitamin D 2 and 25(OH)D 2 were mapped to foods and beverages that were commonly consumed by AHS participants.Usual vitamin D intakes (µg day -1 ) by sex and age group were estimated using the National Cancer Institute method. Results: Assuming a 25(OH)D bioactivity factor of 1, mean daily intakes of vitamin D ranged between 1.84 and 3.25 µg day -1 . Compared to the estimated average requirement of 10 µg day -1 recommended by the Institute of Medicine, more than 95% of people had inadequate vitamin D intakes. We estimated that no participant exceeded the Institute of Medicine's Upper Level of Intake (63-100 µg day -1 , depending on age group). Conclusions: Usual vitamin D intakes in Australia are low. This evidence, paired with the high prevalence of vitamin D deficiency in Australia, suggests that data-driven nutrition policy is required to safely increase dietary intakes of vitamin D and improve vitamin D status at the population level. K E Y W O R D S 25-hydroxyvitamin D, Australia, food, usual intakes, vitamin D Key points • We quantified usual intakes of vitamin D in the Australian population using up-to-date, comprehensive vitamin D composition data and nationally representative food consumption data.