Estimated vitamin D synthesis and dietary vitamin D intake among Asians in two distinct geographical locations (Kuala Lumpur, 3°N v. Aberdeen, 57°N) and climates

Objective: To compare the contributions of UVB exposure and diet to total vitamin D among Asians living in Kuala Lumpur (KL) and Aberdeen (AB). Design: Longitudinal study. Setting:UVB exposure (using polysulfone film badges) and skin colour and dietary vitamin D intake (by web-based questionnaire) were measured at each season in AB and during south-west (SWM) and north-east monsoons (NEM) in KL. Subjects: One hundred and fifteen Asians in KL and eighty-five Asians in AB aged 20-50 years. Results Median summer UVB exposure of Asians in AB (0.25 SED/d) was higher than UVB exposure for the KL participants (SWM=0.20 SED/d, P = 0.02; NEM = 0.14 SED/d, P < 0.01). UVB exposure was the major source of vitamin D in KL year-round (60%) but only during summer in AB (59%). Median dietary vitamin D intake was higher in AB (3.50 mu g/d (140 IU/d)), year-round, than in KL (SWM = 2.05 mu g/d (82 IU/d); NEM = 1.83 mu g/d (73 IU/d), P < 0.01). Median total vitamin D (UVB plus diet) was higher in AB only during summer (8.45 mu g/d (338 IU/d)) compared with KL (SWM = 6.03 mu g/d (241 IU/d), P = 0.04; NEM = 5.35 mu g/d (214 IU/d), P < 0.01), with a comparable intake across the full year (AB=5.75 mu g/d (230 IU/d); KL = 6.15 mu g/d (246 IU/d), P = 0.78). Conclusions: UVB exposure among Asians in their home country is low. For Asians residing at the northerly latitude of Scotland, acquiring vitamin D needs from UVB exposure alone (except in summer) may be challenging due to low ambient UVB in AB (available only from April to October).