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

Abstract

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 r2=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.

Vitamin D and Calcium Insufficiency-Related Chronic Diseases: an Emerging World-Wide Public Health Problem

“…A relatively low value of 5% has been reported for the USA [51]. However, if 50 nM 25-(OH)D is considered the upper reference limit, on the average one-half of the adult population in Europe [26,38,44–47], Western Canada [52], Australia [53,54] and New Zealand [55] presents with vitamin D insufficiency, whereas only one-third is afflicted in the USA [51] (Table 2). …”

So depression is an inflammatory disease, but where does the inflammation come from?

“…Low levels of Vitamin D, particularly 25-hydroxyvitamin D are widespread among Western populations [219], making it the most prevalent deficiency state. Low Vitamin D is linked to a diversity of adverse health outcomes, such as osteoporosis and cancer [220].…”

The ABC of Vitamin D: A Qualitative Study of the Knowledge and Attitudes Regarding Vitamin D Deficiency amongst Selected Population Groups

“…Because of its relationship to UV exposure, vitamin D status is associated with geography. There is greater insufficiency of vitamin D at high latitudes, like northern European countries [5,6,7], but it is also found at low latitudes, like Australia, where UV levels are generally high and rates of skin cancer are amongst the highest in the world [8,9]. This co-occurrence of vitamin D insufficiency and skin cancer is puzzling and has led to the development of guidelines for a balanced approach to sun exposure for both the public [10,11] and health professionals [12].…”