Vitamin D status in South Korean population: Seven-year trend from the KNHANES

Vitamin D deficiency has become one of the most prevalent health problems in modern society. However, there has been no study that has reported the trend of vitamin D status in Asia. We performed an observational study to investigate the trend of vitamin D status in South Korea based on a representative national database acquired from the Korea National Health and Nutrition Examination Surveys (KNHANES) conducted from 2008 to 2014. A total of 39,759 patients were included in the final analyses. Serum 25-hydroxyvitamin D (25 (OH)D) levels were measured by radioimmunoassay. The overall mean serum level of 25 (OH)D was 45.7 nmol/L in males and 40.9 nmol/L in females in KNHANES 2008 to 2014. There was a significant trend toward lower serum 25 (OH)D levels from 2008 to 2014 in males by -1.2 (95% confidence interval [CI] -1.5 to -0.9) nmol/L per year and in female by -0.7 (95% CI -0.9 to -0.4) nmol/L per year. The overall mean serum level of 25 (OH)D in 2008 was 53.0 nmol/L in males and 45.7 nmol/L in females. It decreased to 43.2 nmol/L in males and 39.2 nmol/L in females in 2014. Vitamin D deficiency, defined as the serum 25 (OH)D level of