Vitamin D status of women in the Geelong Osteoporosis Study: association with diet and casual exposure to sunlight

Pasco, Julie A., Henry, Margaret J., Nicholson, Geoff C., Sanders, Kerrie M. and Kotowicz, Mark A. (2001) Vitamin D status of women in the Geelong Osteoporosis Study: association with diet and casual exposure to sunlight. Medical Journal of Australia, 175 8: 401-405.

Author Pasco, Julie A.
Henry, Margaret J.
Nicholson, Geoff C.
Sanders, Kerrie M.
Kotowicz, Mark A.
Title Vitamin D status of women in the Geelong Osteoporosis Study: association with diet and casual exposure to sunlight
Journal name Medical Journal of Australia   Check publisher's open access policy
ISSN 0025-729X
1326-5377
Publication date 2001-10
Sub-type Article (original research)
Volume 175
Issue 8
Start page 401
End page 405
Total pages 5
Place of publication Strawberry Hills, NSW, Australia
Publisher Australasian Medical Publishing Company
Language eng
Formatted abstract
Objective:
To assess vitamin D intake and casual exposure to sunshine in relation to serum 25-hydroxyvitamin D (25OHD) 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, 218 000), which includes the city of Geelong (latitude 38° south) in Victoria.

Main outcome measures:
Vitamin D intake; serum 25OHD 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 25OHD levels was observed for sunbathing frequency before and after adjusting for age (P < 0.05). During winter (May-October), serum 25OHD levels were dependent on vitamin D intake (partial r2 = 0.01; P < 0.05) and were lower than during summer (November-April) (age-adjusted mean, 59 nmol/L [95% CI, 57-62] v 81 nmol/L [95% CI, 78-84]; P < 0.05). No association was detected between serum 25OHD and vitamin D intake during summer. The prevalences of low concentrations of serum 25OHD 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.
Keyword D deficiency
Secondary hyperparathyroidism
D supplementation
Australian women
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Medicine Publications
 
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