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Vitamin D status of women in the Geelong Osteoporosis Study: association with diet and casual exposure to sunlight
Author(s) -
Pasco Julie A,
Henry Margaret J,
Nicholson Geoff C,
Sanders Kerrie M,
Kotowicz Mark A
Publication year - 2001
Publication title -
medical journal of australia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.904
H-Index - 131
eISSN - 1326-5377
pISSN - 0025-729X
DOI - 10.5694/j.1326-5377.2001.tb143643.x
Subject(s) - vitamin d and neurology , sunbathing , medicine , sunlight , vitamin d deficiency , population , cross sectional study , physiology , zoology , biology , environmental health , physics , dermatology , astronomy , pathology
Objective To assess vitamin D intake and casual exposure to sunshine in relation to serum 25‐hydroxyvitamin D (250HD) levels. Design Cross‐sectional study of a population‐based, random sample of women aged 20–92 years, assessed between 1994 and 1997. Setting and participants 861 women from the Barwon Statistical Division (population, 218000), which includes the city of Geelong (latitude 38° south) in Victoria. Main outcome measures Vitamin D intake; serum 250HD level; season of assessment; exposure to sunshine. Results Median intake of vitamin D was 1.2 μg/day (range, 0.0–11.4 μg/day). Vitamin D supplements, taken by 7.9% of participants, increased intake by 8.1% to 1.3 μg/day (range, 0.0–101.2 μg/day) ( P < 0.001). A dose–response relationship in serum 250HD levels was observed for sunbathing frequency before and after adjusting for age ( P <0.05). During winter (May–October), serum 250HD levels were dependent on vitamin D intake (partial r 2 =0.01; P <0.05) and were lower than during summer (November–April) (age‐adjusted mean, 59nmol/L [95% CI, 57–62] v 81 nmol/L [95% CI, 78–84]; P <0.05). No association was detected between serum 250HD and vitamin D intake during summer. The prevalences of low concentrations of serum 250HD were, for <28 nmol/L, 7.2% and 11.3% overall and in winter, respectively; and, for < 50 nmol/L, 30.0% and 43.2% overall and in winter, respectively. Conclusions At latitude 38° south, the contribution of vitamin D from dietary sources appears to be insignificant during summer. However, during winter vitamin D status is influenced by dietary intake. Australia has no recommended dietary intake (RDI) for vitamin D, in the belief that adequate vitamin D can be obtained from solar irradiation alone. Our results suggest that an RDI may be needed.