Lifestyle factors including less cutaneous sun exposure contribute to starkly lower vitamin D levels in U . K . South Asians compared with the white population

Summary Background Long‐standing concerns over the vitamin D status of S outh A sian adults in the U . K . require studies using statistically valid sample sizes to measure annual variation and contributory lifestyle factors. Objectives To measure annual variation in the vitamin D status of U . K . S outh A sians, to determine the associated lifestyle influences, and to compare these with a similar study of white adults. Methods A single‐centre, prospective cohort study measuring circulating 25‐hydroxyvitamin D [25( OH ) D ], sunlight exposure levels and lifestyle factors for 1 year in 125 ambulant S outh A sian adults with sun‐reactive skin type V , aged 20–60 years, in G reater M anchester, U . K . (53·5°N). Results The 25( OH ) D levels of S outh A sians were alarmingly low. In summer, their median 25( OH ) D level was 9·0 ng mL −1 , [interquartile range ( IQR ) 6·7–13·1], falling to 5·8 ng mL −1 (IQR 4·0–8·1) in winter. This compared with values in the white population of 26·2 ng mL −1 (IQR 19·9–31·5) in summer and 18·9 ng mL −1 IQR (11·6–23·7) in winter. Median daily dietary vitamin D was lower in S outh A sians (1·32 μg vs. 3·26 μg for white subjects) and was compounded by low supplement use. Despite similar times spent outdoors, ultraviolet ( UV ) dosimeters recorded lower personal UV exposure among S outh A sians, indicating sun avoidance when outside, while sun exposure diaries recorded lower amounts of skin surface exposure. Conclusions The majority of S outh A sians never reached sufficiency in vitamin D status. Lifestyle differences, with lower oral intake, sun exposure and rates of cutaneous production due to darker skin, indicate that standard advice on obtaining sufficient vitamin D needs modification for the S outh A sian community in the U . K .