Necessity of daily 1000-IU vitamin D supplementation for maintaining a sufficient vitamin D status

The changes in the serum 25-hydroxyvitamin D (25(OH)D) concentrations after daily 1000-IU vitamin D intake for 3 months (3-month-VD), 6 months (6-month-VD) and then 6-month cessation of vitamin D intake (6-month-VD cessation) were examined. The serum 25(OH)D levels in 11 male and 16 female subjects were 12.1 ± 3.5 ng / mL at baseline, increased to 27.1 ± 4.7 ng / mL at 3-month-VD, 28.5 ± 5.1 ng / mL at 6-month-VD and decreased to 16.4 ± 4.0 ng / mL at 6-month-VD cessation. The present study suggested that a vitamin D intake of 1000 IU / day is required to maintain the 25(OH) D concentration at 30 ng / mL or higher without vitamin D intoxication.