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

Study answer

What this study found

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…

Study & population

Nationally representative cross-sectional analysis from the National Adult Nutrition Survey.

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.

Key limitation

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…

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Original abstract