Over 50% of the Korean population above 49 years have low blood vitamin D concentrations increasing the risk of osteoporosis, says a new study from Korea.
In the observational study, the 25-hydroxyvitamin D (25[OH]D) blood concentrations of 1,451 men and 1,870 women aged 49 years and above were analyzed (1). The study results showed that 8.7% of the men and 17.9% of the women had serum 25(OH)D values below 12.1 ng/mL (30nM) and 50.4% resp. 66.3% had values below 20.4 ng/mL (51nM)– vitamin D concentrations defined as insufficient. Furthermore, bone mineral density (BMD) of the participants’ femurs increased until 25(OH)D concentration dropped below
20.4 ng/mL; no significant changes were observed thereafter. Serum 25(OH)D values of 12.1 ng/mL and 20.4 ng/mL were associated with an increased risk of osteoporosis, while a value of 30 ng/mL (75.0 nmol/L) was not. 25(OH)D concentrations varied in relation to the season of the year, being highest in summer and lowest in spring.
The researchers commented that these findings are in line with earlier studies that have found that the Korean population has the lowest absolute concentration of serum 25(OH)D (17.6 ng/mL) compared to populations in other countries from a wide variety of latitudes and that vitamin D inadequacy, defined as serum 25(OH)D concentrations below 30 ng/mL, was highest in Korea with 92% (2). Also in agreement with the new results are earlier observations (3) indicating that adequate serum 25(OH)D concentrations for bone health may be lower than previously suggested. Accordingly, concentrations of 20 ng/mL might be sufficient.
The WHO defines vitamin D insufficiency as a serum 25(OH)D concentration below 20 ng/mL, and concen-trations below 10 ng/mL are considered vitamin D deficient. However, many observational studies suggest that the optimal serum 25(OH)D concentration for bone health is greater than 30 ng/mL and that concen-trations between 30 and 20 ng/mL are considered vitamin D insufficient and those below 20 ng/mL represent deficiency.