New research suggests that among kidney transplant patients, low 25(OH)D levels increases the risk of long-term mortality and are associated with a decline in estimated glomerular filtration rate. The study also showed an association between mortality and activated vitamin D, but the relationship was dependent on overall kidney function.
When researchers look at vitamin D’s role in kidney-related outcomes, they must do so with a unique perspective. Unlike most other organ-related conditions, the kidneys are intimately tied to vitamin D metabolism.
After vitamin D has been carried through the bloodstream, it is sent to the liver to be converted into the circulating form, 25(OH)D. From there, the 25(OH)D is sent to the kidneys as well as other cells and tissues in the body to be converted to the activated form that the body uses.
The kidneys contain the highest amount of the enzyme responsible for converting inactivated vitamin D, 25(OH)D, into its activated form, 1,25(OH)D. While other cells and tissues hold this ability, the kidneys are predominantly involved in the final stages of the vitamin D metabolic pathway, when it is activated and used.