Environmental and genetic determinants of vitamin D status among older adults in London, UK.

•We report that 65% of a cohort of older adults living in sheltered accommodation in London, UK, were vitamin D deficient (serum 25-hydroxyvitamin D concentrations <50nmol/L).•Sampling in winter/spring, non-white ethnic origin and lack of vitamin D supplement use were independently associated with lower vitamin D status.•None of a panel of 15 single nucleotide polymorphisms in DBP, DHCR7, CYP2R1, CYP27B1, CYP24A1 or VDR associated with serum 25-hydroxyvitamin D concentrations in this population.•Vigorous efforts should be made to improve uptake of vitamin D supplements among older adults in the UK in order to protect them against vitamin D deficiency.