Pharmacokinetics and effects of demographic factors on blood 25(OH)D3 levels after a single orally administered high dose of vitamin D3

Aim: To examine the biological consequences and demographic factors that might affect the pharmacokinetics of vitamin D3 after a single high dose intervention in a young Chinese population with vitamin D insufficiency status. Methods: A total of 28 young subjects (25 to 35 years old) with vitamin D insufficiency status [serum 25(OH) D <30 ng/mL] was recruited in Shanghai, China. The subjects were orally administered a single high dose of vitamin D3 (300 000 IU). Baseline characteristics and blood samples were collected at d 0, 1, 2, 3, 7, 28, 56, 84 and 112 after the intervention. The blood biomarker levels were determined with standardized methods. Results: The intervention markedly increased the blood 25(OH) D3 levels within the first five days (mean T-max = 5.1 +/- 2.1 d) and sustained an optimal circulating level of 25(OH) D3 (>= 30 ng/mL) for 56 d. After the intervention, body weight and baseline 25(OH) D3 levels were significantly correlated with circulating 25(OH) D3 levels. No adverse events and no consistently significant changes in serum calcium, creatinine, glucose, parathyroid hormone, vitamin D binding protein, or the urinary calcium/creatinine ratio were observed. However, there was a significant increase in phosphorus after the vitamin D3 intervention. Total cholesterol and triglyceride levels were decreased at the end of the trial. Conclusion: The pharmacokinetics of vitamin D after intervention were influenced by baseline 25(OH) D3 levels and the body weight of the subjects. The results suggest that a single high oral vitamin D3 intervention is safe and efficient for improving the vitamin D status of young Chinese people with vitamin D insufficiency.