Serum 25-hydroxyvitamin D concentrations of New Zealanders aged 15 years and older

Introduction: Vitamin D plays an important role in bone health. Our purpose was to measure serum 25-hydroxyvitamin D concentrations and their determinants in a national sample (n=2,946) of New Zealanders aged 15 years and over. Findings: Mean (99% CI) serum 25-hydroxyvitamin D concentrations were 47 (45-50) nmol/l in women and 52 (49-55) nmol/l in men. Mean concentrations in New Zealand European and Others (NZEO, n=2,440), Mori (n=370), and Pacific (n=136) were 51 (49-53), 42 (38-46) and 37 (33-42) nmol/l, respectively. Three percent of New Zealanders had serum 25-hydroxyvitamin D concentrations indicative of deficiency (≤17.5 nmol/l); 48% and 84% were insufficient based on cutoffs of ≤50 and ≤80 nmol/l. Determinants of serum 25-hydroxyvitamin D concentrations in women were age, ethnicity, obesity, latitude and season; determinants in men were ethnicity and season. Serum 25-hydroxyvitamin D in women declined with age; mean concentration was 13 (8-18) nmol/l lower in women 65 years or older and 9 (5-13) nmol/l lower in women 45-64 years compared with women 15-18 years. Spring to summer differences in serum 25-hydroxyvitamin D were 31 (28-34) and 28 (25-31) nmol/l in women and men, respectively. Obese women had lower vitamin status than normal-weight women by 6 (3-10). Women living in the South Island had a mean serum 25-hydroxyvitamin D that was 6 (3-9) nmol/l lower than women living in the North Island. Ethnicity and season are the major determinants of serum 25-hydroxyvitamin D in New Zealanders. Conclusion: The high prevalence of vitamin D insufficiency in New Zealanders, particularly in older women, may warrant strategies to improve vitamin D status.