New NZ research on vitamin D

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.

For further information, or to talk to an expert on vitamin D, please contact the Science Media Centre on tel: 04 499 5476 or email: