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

Med J Aust. 2001 Oct 15;175(8):401-5. doi: 10.5694/j.1326-5377.2001.tb143643.x.


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, 218000), which includes the city of Geelong (latitude 38 degrees 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 microg/day (range, 0.0-11.4 microg/day). Vitamin D supplements, taken by 7.9% of participants, increased intake by 8.1% to 1.3 microg/day (range, 0.0-101.2 microg/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, 59nmol/L [95% Cl, 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 <28nmol/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 degrees 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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Age Factors
  • Aged
  • Aged, 80 and over
  • Australia
  • Cross-Sectional Studies
  • Dietary Supplements*
  • Female
  • Humans
  • Middle Aged
  • Multivariate Analysis
  • Osteoporosis / physiopathology*
  • Osteoporosis / prevention & control*
  • Population Surveillance
  • Probability
  • Regression Analysis
  • Risk Assessment
  • Sampling Studies
  • Seasons
  • Sensitivity and Specificity
  • Sunlight*
  • Vitamin D / administration & dosage*
  • Vitamin D / blood*


  • Vitamin D