The Role of Vitamin D in Chronic Kidney Disease (CKD) Patients

Chronic kidney disease (CKD) is a progressive condition often accompanied by vitamin D deficiency or insufficiency. Extensive research indicates a high prevalence of vitamin D deficiency in CKD patients, which is closely associated with disorders of bone mineral metabolism, cardiovascular diseases, diabetes, and increased mortality. Vitamin D deficiency not only impacts skeletal health but is also closely linked to CKD progression and the development of complications. Thus, vitamin D supplementation plays a critical role in the management of CKD.

Causes of Vitamin D Deficiency and Its Relationship with CKD

The causes of vitamin D deficiency in CKD patients are multifactorial, primarily including the following:

1.Reduced Renal Synthesis

Declining kidney function in CKD patients leads to decreased synthesis of 1,25-dihydroxyvitamin D (active vitamin D), impairing calcium absorption and bone mineral metabolism.

2.Inadequate Dietary Intake

Many CKD patients have insufficient dietary intake of vitamin D, particularly those with limited sun exposure.

3.Increased Vitamin D Catabolism

Elevated levels of fibroblast growth factor 23 (FGF23) in CKD patients accelerate vitamin D breakdown.

4.Vitamin D Loss During Dialysis

Dialysis patients experience vitamin D loss through dialysate, resulting in persistently low serum vitamin D levels.

Figure1. Overview of Vitamin D Metabolism. Vitamin D is obtained through skin exposure to ultraviolet light or dietary sources.

Therapeutic Effects and Epidemiological Data on Vitamin D Supplementation

 Studies demonstrate significant clinical benefits of vitamin D supplementation in CKD patients. Below are key epidemiological findings and research outcomes:

1.Prevalence of Vitamin D Deficiency in CKD Patients

A large-scale epidemiological study found that approximately 80% of CKD patients exhibit vitamin D deficiency or insufficiency, highlighting the widespread nature of this issue in the CKD population.

2.Impact of Vitamin D Supplementation on PTH Levels

A randomized controlled trial involving CKD stages 3–5 patients showed that weekly supplementation with 50,000 IU of vitamin D3 (cholecalciferol) significantly increased serum 25(OH)D levels and effectively reduced parathyroid hormone (PTH) levels. Lower PTH levels help mitigate bone mineral disorders and prevent secondary hyperparathyroidism (SHPT).

3.Therapeutic Effects in Pediatric Patients

In children with CKD, vitamin D supplementation not only elevates serum 25(OH)D levels but also delays or ameliorates SHPT and reduces bone mineral disease.

4.Research Data in Adult Patients

Studies in adult CKD patients indicate that vitamin D supplementation improves bone density, reduces fracture risk, and decreases cardiovascular events. For example, one study found that vitamin D supplementation significantly enhances cardiovascular health and slows arterial stiffness progression in CKD patients.

Figure2. Renal Vitamin D Metabolism and Major Regulators of 1α‑Hydroxylase and 24‑Hydroxylase

Vitamin D Supplementation Strategies for Dialysis Patients

Dialysis patients, due to severely impaired kidney function, have minimal endogenous vitamin D synthesis and thus rely on exogenous supplementation. According to European consensus guidelines, dialysis patients should receive vitamin D3 (cholecalciferol) to maintain serum 25(OH)D levels within the optimal range.

Effects of Vitamin D Supplementation in Dialysis Patients

Research shows that weekly supplementation with 50,000 IU of vitamin D3 in dialysis patients significantly increases serum 25(OH)D concentrations, improving bone mineral metabolism and cardiovascular health. For instance, a study in dialysis patients observed reduced PTH levels, improved bone density, and a lower risk of cardiovascular disease following vitamin D supplementation.

Figure 3. Extrarenal Vitamin D Metabolism and Roles of 1α-Hydroxylase and 24-Hydroxylase

Vitamin D Supplementation Post-Kidney Transplantation

Kidney transplant recipients often experience vitamin D deficiency, particularly in the early post-transplant period, due to immunosuppressant use and incomplete renal function recovery.

Research Findings in Kidney Transplant Patients

Vitamin D supplementation in kidney transplant recipients reduces osteoporosis incidence and improves bone mineral metabolism. A study demonstrated that supplementation significantly lowers PTH levels and enhances bone health in this population.

Figure 4. Association Between Genetically Determined 25(OH)D Levels and All-Cause or Cause-Specific Mortality

Clinical Recommendations and Vitamin D Supplementation Strategies

Based on current evidence, the European Renal Association recommends vitamin D supplementation for CKD patients, particularly those with serum 25(OH)D levels below 50 nmol/L.

1.Dosage of Vitamin D Supplementation

Adult and pediatric CKD patients should receive supplementation tailored to their vitamin D status. The recommended initial dose is 50,000 IU weekly for 12 weeks, followed by a maintenance dose (e.g., 2,000 IU daily).

2.Supplementation Strategies for Dialysis Patients

Dialysis patients require individualized supplementation to maintain serum 25(OH)D levels above 50 nmol/L.

3.Vitamin D Supplementation in Kidney Transplant Patients

Post-transplant patients should undergo regular monitoring of serum 25(OH)D levels and receive appropriate supplementation to reduce osteoporosis and cardiovascular risks.

Figure 5. 25(OH)D Responses from 16 Study Groups in Randomized Controlled Trials of Nutritional Vitamin D in Adults with CKD

Vitamin D supplementation holds significant clinical importance for CKD patients, particularly children, adults, dialysis patients, and kidney transplant recipients. Appropriate supplementation improves bone density, controls PTH levels, and reduces fracture and cardiovascular risks.

References

[1].Jørgensen H. S., Vervloet M., Cavalier E., et al. The role of nutritional vitamin D in CKD-MBD in children and adults with CKD, on dialysis and after kidney transplantation – a European consensus statement. Nephrol Dial Transplant. 2025.

[2].U.S. Department of Health and Human Services. Dietary Supplement Fact Sheet: Vitamin D. National Institutes of Health, 2021.

[3].Levin A., et al. "Effect of Vitamin D on Cardiovascular Events and Mortality in Chronic Kidney Disease: A Systematic Review." J Am Coll Cardiol. 2020.

[4].Tsujita M., et al. "Effects of Vitamin D Supplementation on Bone Mineral Density in Kidney Transplant Recipients." Transplantation Proceedings. 2019.

[5].Kumar A., et al. "Safety and Efficacy of SGLT-2 Inhibitors in CKD: An Update." Kidney International Reports. 2024.