25-Hydroxyvitamin D Status and Its Predictors in Greek and Cypriot Subsets of the UK Biobank Cohort

Objective: Studies show a high prevalence of vitamin D deficiency in Greece and Cyprus despite an abundance of sunlight. We investigate the vitamin D status of Greeks and Cypriots living in the UK, where sunlight availability is more limited. Design: Cross-sectional study of serum 25-hydroxyvitamin D (25(OH)D) using the UK Biobank cohort. Setting: The UK Biobank is a study of over 500K UK dwelling participants, with baseline measurements from 2006-2010. Participants: A sample of 325 Greek/Cypriot and 4158 British/Irish participants (aged 40-69 years). Results: The Greeks/Cypriots had statistically significantly lower median serum 25-hydroxyvitamin D (25(OH)D) (40.3 nmol/L) compared to the British/Irish (47.6 nmol/L). Eleven percent of British/Irish and 22.8% of Greeks/Cypriots had serum 25(OH)D < 25 nmol/L. Being exposed to summer sunlight for >30 min/d, as well as having a blood draw in summer or autumn, was statistically significantly associated with lower odds of 25 (OH))D < 50 nmol/L. Living in Scotland, having a winter blood draw, and not using a vitamin D-containing supplement were associated with increased odds of 25(OH)D < 50 nmol/L. Ethnicity was not a predictor of 25(OH)D < 50 nmol/L after confounder adjustment (Greek/Cypriot OR = 1.18 (95% CI 0.85, 1.63; British/Irish OR = 1.0). Conclusions: UK dwelling Greeks/Cypriots have a higher prevalence of vitamin D deficiency (<25 nmol/L) compared to the British/Irish population, but evidence from the literature is mixed as to whether they have a higher prevalence than when living in their country of origin. Public health interventions are required to improve 25(OH)D status in UK ethnic minority groups.