Department of Nutrition and Food Hygiene;
College of Public Health;
Zhengzhou University;
Zhengzhou 450001;
Henan;
China;
Department of Environmental Hygiene;
College of Public Health;
Zhengzhou University;
Zhengzhou 450001;
Henan;
China;
Department of Epidemiological;
College of Public Health;
Zhengzhou University;
Zhengzhou 450001;
Henan;
China;
Polymorphisms; CYP2R1; Gene; Serum; Vitamin; D; Chinese; Rural; Population;