Vitamin d status in Korea.

The majority of the vitamin D in our body is produced by cutaneous synthesis in response to sunlight. As more and more people live in cities and spend the bulk of their time indoors, it can be difficult to get sufficient sun exposure for adequate cutaneous production of vitamin D. Therefore, vitamin D insufficiency has become a very common health problem worldwide. The Korea National Health and Nutrition Examination Survey IV 2008 showed that the prevalence of vitamin D insufficiency, defined as a serum 25-hydroxyvitamin D [25(OH)D] level below 50 nmol/L, was 47.3% in males and 64.5% in females. Only 13.2% of males and 6.7% of females had a serum 25(OH)D level of greater than 75 nmol/L. In Korea, vitamin D insufficiency was more prevalent in young adults than in elderly people, likely due to the indoor lifestyle of younger people. Compared with the United States and Canada, Korea has a lower mean 25(OH)D level and a higher prevalence of vitamin D insufficiency. To improve the vitamin D status of the Korean population, more aggressive policies on food fortification and vitamin D supplementation are needed.