Vitamin D Intervention Trial in Healthy Chinese

Recent epidemiological studies suggested that serum 25-hydroxyvitamin D [25(OH)D] concentration ≥75 nmol/L appeared to be optimal for preventing cardiometabolic diseases and improving bone health. To achieve this goal, a daily intake of 1000 IU or equivalent amount from other sources, is needed, which is twice as much as the RDA recommended by Chinese Nutrition Society. Meanwhile,epidemiological evidences show that large proportions of Chinese may suffer vitamin D insufficiency or deficiency whereas the current RDA in China might be too low to provide adequate vitamin D for people's health.

In order to fill up this gap, therefore, it is essential to determine the dose-response between the doses of vitamin D3 supplements and raised serum levels of 25(OH)D and also the dose of vitamin D3 required to achieve circulating 25(OH)D ≥ 75 nmol/L.Ultimately, the current study will provide important evidence for establishing optimal vitamin D requirement for Chinese people

Inclusion criteria

• Age: 20-45 years. with vitamin D deficiency (25(OH)D < 50 nmol/l)

Exclusion criteria

• BMI < 18.5 kg/m2, or BMI ≥ 25 kg/m2
• Total intake of calcium from diet or supplements >1200mg/d, or fasting serum calcium level ≥2.75 mmol/l
• Participating in other clinical studies within previous 3 months
• Taking vitamin D supplements within previous 3 months
• Using medications that may affect vitamin D metabolism in previous 3 months;
• Concomitant with clinical conditions, like liver dysfunction (serum alanine transaminase (ALT) ≥40 U/L; and/or aspartate transaminase (AST) ≥40 U/L; Glutamyl transpeptidase （GGT）≥50 U/L; serum creatinine < 50 or > 120 µmol/L; urea nitrogen (UN) < 7 or > 18 mg/dl, and/or urine acid <90 or >420 µmol/L; which may affect vitamin D metabolism;
• History of drug or alcohol abuse (>40 g/d)
• Women during pregnancy or lactation
• Individuals with mental disorders or current use of antidepressants, the conditions which may affect him or her understanding and unwillingness to the intervention;
• Having clinically diagnosed AIDS, hepatitis A, hepatitis B, tuberculosis and other infectious diseases.