Further Evidence: Sunlight Alone is Insufficient to Rise Vitamin D Levels in Non-Western Immigrants
Wicherts et.al. ( Wicherts. 2010 ) published the results of an investigation into the effectiveness of a) sun exposure or b) supplementation with daily 800 IU or 100,000 IU once in three months on serum 25(OH)-D3 levels in 211 otherwise healthy non-western immigrant in the Netherlands. As you can see in table 1, the initial high dose of 100.000 IU raised 25(OH)D levels significantly faster but to a lower extent than the 800 IU daily dosing: Table 1: Proportion (%) of participants with serum 25(OH)D<25, 25−50, 50−75, or >75 nmol/l at baseline, 3, 6, and 12 months according to treatment group 800 IU/day, 100,000 IU/3 months or sunshine exposure ( Wicherts. 2010. Table 2 ) Otherwise, Wickerts' study confirms the results of earlier investigations, mean serum 25(OH)D increased to 53 nmol/l with 800 IU/day, to 50.5 nmol/l with 100,000 IU/3 months, and to 29.1 nmol/l with advised sunlight exposure. ...