Dietary vitamin D intake in low ultraviolet irradiation seasons is associated with a better nutritional status of vitamin D in Korean adults according to the 2013-2014 National Health and Nutrition Examination Survey.

Vitamin D deficiency poses a global public health burden; however, there are limited studies on the relationship between vitamin D intake and serum 25-hydroxyvitamin D (25(OH)D) concentration in Koreans with a special focus on seasonal variables. We hypothesized that the relationship between serum 25(OH)D and vitamin D intake levels in Korean adults would change with the seasons, and that the distribution of food sources for vitamin D would vary according to sex and age. We established a new version of the food vitamin D database, analyzed the Korean National Health and Nutrition Examination Survey 2013 to 2014 data (n = 3257), and calculated the vitamin D intake of Koreans using a complex sample model. We found that the daily vitamin D intakes of men and women were 4.09 ± 0.26 µg and 2.87 ± 0.17 µg and their 25(OH)D levels were 16.98 ± 0.24 ng/mL and 15.62 ± 0.21 ng/mL, respectively. A significant positive correlation was observed between vitamin D intake and serum 25(OH)D levels in all participants. Serum 25(OH)D levels in the spring and winter (low ultraviolet irradiation seasons) were significantly higher in the 3rd tertile of vitamin D intake than in the first tertile. Fish and shellfish were the main sources of vitamin D for Koreans, the consumption of which was the least in the 19- to 29-year-old group; additionally, their serum 25(OH)D level was the lowest. In conclusion, insufficient vitamin D intake during low ultraviolet irradiation seasons is associated with lower levels of serum 25(OH)D.