Targetted sun exposure guidance for South Asians living at northerly latitude could assist avoidance of vitamin D deficient status (25[OH]D

Low vitamin D status remains prevalent in S.Asians living at northerly latitudes despite dietary advice. It is known that following general recommendations on summer-sunlight exposure (geared for white skinned people) has little impact on their vitamin D status. As their skin cancer risk is low, increased sun-exposure may be appropriate to assist their status. We thus examined the efficacy of a dose-range of simulated UK summer sunlight exposures in raising vitamin D status in adults of S.Asian ethnicity. Healthy S.Asians (n=60, 20-60y) received one of 6 UVR exposures ranging from 0.65-3.9 SED, equivalent to 15-90 minutes midday summer-sunlight at 53.5°N (Manchester, UK), 3x/week for 6 weeks. This occurred in a whole body cabinet (95% 320-400 nm, 5% 290-320 nm), while wearing casual clothes to reveal 35% skin area. Serum 25-hydroxyvitamin D (25[OH]D) was measured weekly. Mean dietary vitamin D intake was 2 µg/day (range 0.12-14.48). At baseline, all completing participants (n=51) were vitamin D insufficient (25[OH]D <20 ng/mL) with 90% deficient (<10 ng/mL, a level associated with osteomalacia and rickets). Post-course, only 6/51 attained 20 ng/mL 25(OH)D. Level of 25(OH)D increased in all groups (P≤0.01). Rise in 25(OH)D increased with UVR dose to 3.25 SED, this group had a mean±SD rise of 12.7±7.8 ng/mL (P<0.01) and attained 18.0±6.2 ng/mL post-course. Notably, the majority (94%) of those volunteers receiving exposure doses ≥1.95 SED achieved 25(OH)D >10 ng/mL (n=31, mean±SD 15.7±5.0 ng/mL), equivalent to ≥45 minutes unshaded midday sunlight exposure at UK latitude. Targeted sunlight exposure guidance to S.Asians could enhance vitamin D status to a level to avoid deficiency. However, more effective advice on oral vitamin D intake is required for S.Asians living at northerly latitude to achieve 25(OH)D ≥20 ng/mL.