Vitamin D status of Irish adults: findings from the National Adult Nutrition Survey

British Journal of Nutrition
Q1
Aug 2012
Citations:124
Influential Citations:5
Observational Studies (Human)
83
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Methods
Nationally representative cross-sectional analysis from the National Adult Nutrition Survey. Participants: Irish adults aged 18–84 years (n=1500; 1132 provided blood samples). Quota sampling to achieve 50:50 sex within age groups; data collected Oct 2008–Apr 2010; serum 25(OH)D measured by ELISA; supplement use assessed by questionnaire and 4-day diary; data weighted to represent the Irish adult population; ethnicity predominantly Caucasian (~99.5%).
Intervention
Vitamin D–containing supplements; self-administered; daily doses with median 200 IU/day; among users, 67.2% took ≤200 IU/day, 15.1% took 200–<400 IU/day, and 3.5% took ≥1000 IU/day; duration not reported; taken orally.
Results
Year-round, 6.7% had serum 25(OH)D <30 nmol/L; winter prevalence for <30, <40, <50, and <75 nmol/L was 11.1%, 31.1%, 55.0%, and 84.0% respectively. Supplement users (17.5% of adults) had higher mean serum 25(OH)D than non-users in both seasons; winter mean for users was 66.1 nmol/L, similar to non-users in summer (64.3 nmol/L). Seasonality in 25(OH)D was attenuated in supplement users (summer–winter change 13.9 nmol/L in non-users vs 5.1 nmol/L in users). Overall, supplement use reduced the prevalence of low vitamin D, but at current uptake (17.5%), population-level impact is limited; food fortification strategies should be explored. The data provide the first nationally representative snapshot of vitamin D status in Irish adults.
Limitations
Cross-sectional design; observational associations cannot establish causality; subgroups were small; sample with blood samples (n=1132) may limit precision; population was predominantly Caucasian; sun exposure not directly measured; self-reported supplement use and diary data may have reporting bias; some seasonal estimates rely on modeling assumptions.

Abstract

Previous national nutrition surveys in Irish adults did not include blood samples; thus, representative serum 25-hydroxyvitamin D (25(OH)D) data are lacking. In the present study, we characterised serum 25(OH)D concentrations in Irish adults from the...