Three research papers on vitamin D have been published in the New Zealand Medical Journal today (28 November). Jim Bartley, from Green Lane Clinical Centre, Auckland, looks at prevalence of vitamin D deficiency among patients attending a tertiary pain clinic. Results showed that of 177 patients, 3% had 25-hydroxyvitamin D levels <17.5nmol/L – a level associated with osteomalacia, and 32% had 25-hydroxyvitamin D levels <50nmol/L, a level associated with vitamin D deficiency. This study confirms a high prevalence of vitamin D deficiency within a tertiary pain clinic.
A second study, by Mark Bolland (a Research Fellow at the University of Auckland) and colleagues, looked at the effects of seasonal variation of 25-hydroxyvitamin D on diagnosis of vitamin D insufficiency, and recommends that clinicians need to consider the month of sampling when interpreting vitamin D results as seasonal variations can occur (the major biological determinant of serum 25-hydroxyvitamin D levels being ultraviolet light). In New Zealand, a summertime 25-hydroxyvitamin D level of >60-75 nmol/L is generally required to ensure year-round 25-hydroxyvitamin D levels of >50nmol/L.
The final study, by Jennifer Rockell (a PhD candidate from the University of Otago) and colleagues, looked at the implications of vitamin D insufficiency on bone health. Rockell et al. found that mean plasma 25-hydroxyvitamin D concentrations were higher in late summer versus early spring (79 vs 51 nmol/L). The lower levels in early spring were associated with a higher parathyroid hormone (PTH) concentration. Annually recurring cycles of low vitamin D with elevated PTH may contribute to age-related bone loss and increased fracture risk. The authors conclude that strategies to improve the vitamin D status of the population in New Zealand may be needed, such as supplementation and food fortification.
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