evaluated the effect and safety of a single high dose of cholecalciferol in Chinese young people.

Inclusion Criteria:

• Healthy, younger, Chinese Hans aged from 25-35 years, including 25 and 35 years;
• haven't taken vitamin D supplement for the past 6 months;
• with a normal BMI (18-25 kg/m2);
• with baseline serum 25(OH)D < 30 ng/ml;
• be willing to follow the instruction and complete the study.

Exclusion Criteria:

• clinically diagnosed cardiovascular disease, gastrointestinal disease, endocrine, blood, liver, lung, kidney, nerve or mental illness;
• self-reported current use of any dietary supplements containing vitamin D within the 6 months before enrollment;
• Severe anemia (hemoglobin concentration < 70 g/L);
• Serum 25(OH)D ≥ 30 ng/mL at enrollment;
• participating in other research studies within the 3 months before enrollment;
• history of drug dependence or drug abuse;
• History of heavy drinking (drinking 14 cups or more per week, equivalent to 360 mL beer or 150 mL white wine or 45 mL liquor per cup) and smokers (more than 10 cigarette per day);
• clinical abnormal of blood biochemistry, hematology or urine laboratory values;
• current pregnancy or lactation.