Certified Specialist in Renal Nutrition (CSR) Practice Exam 2025 – Complete Test Prep

In the context of chronic kidney disease (CKD) and its associated bone disease, the correct answer is vitamin D. In CKD, the kidneys' ability to convert vitamin D into its active form, calcitriol, is impaired. This results in a deficiency of active vitamin D, which is essential for calcium absorption from the intestine and for maintaining healthy bone metabolism.

As a result of impaired vitamin D metabolism in CKD, individuals often experience disrupted calcium and phosphate balance, leading to secondary hyperparathyroidism and bone disease. Supplementing with active vitamin D (calcitriol) can help manage these issues by promoting better calcium absorption, regulating phosphate levels, and ultimately helping to maintain bone health.

The other micronutrients listed do not have the same direct relationship with CKD-related bone disease. For instance, vitamin C plays a role in various bodily functions but is not specifically increased due to kidney dysfunction. Calcium can be affected by CKD, but the condition typically leads to decreased active vitamin D levels, which may cause lower calcium absorption. Iron is more closely related to anemia often observed in CKD rather than directly associated with bone disease. Therefore, vitamin D is the key micronutrient that is relevant to the bone health complications experienced by individuals with