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Vitamin D status of women in the Geelong Osteoporosis Study : association with diet and casual exposure to sunlight
journal contribution
posted on 2001-10-15, 00:00 authored by Julie PascoJulie Pasco, Margaret Rogers, G Nicholson, K Sanders, Mark KotowiczMark KotowiczObjective: 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.
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.
History
Journal
Medical journal of AustraliaVolume
175Issue
8Pagination
401 - 405Publisher
Australasian Medical Publishing CompanyLocation
Sydney, N.S.W.ISSN
0025-729XeISSN
1326-5377Language
engPublication classification
C1.1 Refereed article in a scholarly journalCopyright notice
2001, Australasian Medical Publishing CompanyUsage metrics
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