Circannual prevalence of vitamin D insufficiency in older and minoritized ethnic adults in Northern Britain: screening outcomes from a clinical trial (ISRCTN13778806)

Vitamin D is essential for bone and metabolic health. Deficiency remains a global health issue, particularly among older adults and ethnic minorities with darker skin pigmentation. Data on circannual variation these groups remain sparse.

This study reports vitamin D status in older adults (≥65 years) and ethnic adults (≥18 years, Fitzpatrick classes IV–VI) in northern Britain during the screening phase of a supplementation trial. Participants were screened for inclusion between December 2024 and August 2025. Serum 25-hydroxyvitamin D (25(OH)D) was assessed in dried blood spots followed by LC-MS/MS analysis.

299 participants were screened. Vitamin D insufficiency or deficiency (<50 nmol/L) was noted in 54.8% of older adults and 72.1% of ethnic individuals. These rates did not decline during summer months. These findings highlight persistently high rates of vitamin D insufficiency across high-risk groups in northern Britain and underscore the inadequacy of sunlight exposure as a corrective measure.