Should water-soluble vitamins, including B vitamins (thiamine, riboflavin, niacin, pantothenic acid, vitamin B6, biotin, and folate) and vitamin C, be supplemented in dialysis patients?

Water-Soluble Vitamin Supplementation in Dialysis Patients

Water-soluble vitamins should be monitored and supplemented in dialysis patients due to increased requirements during kidney failure and large effluent losses during kidney replacement therapy (KRT). 1

Rationale for Supplementation

Increased Requirements and Losses

• Dialysis patients experience significant losses of water-soluble vitamins through:
  • Dialysate effluent losses (approximately 68 mg/day of vitamin C, 0.3 mg/day of folate, and 4 mg/day of thiamine) 1
  • Increased utilization during critical illness 1
  • Decreased dietary intake due to appetite loss and dietary restrictions 2

Documented Deficiencies

• Studies show high prevalence of deficiencies in dialysis patients:
  • Thiamine (B1), vitamin B6, and zinc are the most commonly deficient micronutrients (24.7%, 35.1%, and 44.1% respectively) in chronic hemodialysis patients 1
  • Vitamin C deficiency is common in patients not taking supplements 2
  • Extended hours hemodialysis patients show significantly lower vitamin C and thiamine levels compared to conventional hemodialysis patients 3

Specific Supplementation Recommendations

Priority Vitamins

1. Vitamin C: Special attention required due to significant dialysate losses 1
2. Folate: Critical for reducing homocysteine levels and supporting DNA synthesis 1
3. Thiamine (B1): Essential for preventing metabolic complications 1
4. Vitamin B6: Important for protein metabolism and homocysteine regulation 1
5. Vitamin B12: Necessary for homocysteine metabolism 1
6. Riboflavin (B2): Contributes to homocysteine regulation 1

Dosing Considerations

• Standard multivitamin supplementation after each dialysis session is common practice 4
• However, evidence suggests that standard dosing may lead to excessive levels of some B vitamins while still leaving patients deficient in vitamin C 4
• The K/DOQI guidelines recommend daily vitamin supplementation with special attention to folic acid and vitamins B2, B6, and B12 1

Implementation Algorithm

1. Baseline Assessment:

   • Measure serum levels of water-soluble vitamins before initiating supplementation
   • Pay particular attention to vitamin C, folate, thiamine, and B6 levels

2. Initial Supplementation:

   • Provide water-soluble vitamin supplementation after each dialysis session
   • Focus on replacing documented losses: vitamin C, folate, and thiamine

3. Monitoring and Adjustment:

   • Periodically monitor serum vitamin levels (especially for extended hours dialysis patients)
   • Adjust dosing based on measured levels to avoid both deficiency and excess

4. Special Considerations:

   • Patients on extended hours hemodialysis (>15 hours/week) may require higher doses of vitamin C and thiamine 3
   • Patients with poor nutritional intake may need additional supplementation

Potential Pitfalls and Caveats

• Oversupplementation: Excessive B vitamin supplementation may contribute to left ventricular diastolic dysfunction in CKD patients 5
• Vitamin C Dosing: While supplementation is necessary, high-dose vitamin C (>1g/day) should be avoided as it can increase oxalate formation 2
• Homocysteine Levels: While B vitamin supplementation can lower homocysteine levels, studies have not shown this translates to improved cardiovascular outcomes 1, 2
• Individual Variability: Significant variability exists in vitamin requirements and supplement prescription practices 3

Despite some controversy regarding routine multivitamin supplementation 6, the most recent guidelines from ESPEN (2021,2024) strongly recommend water-soluble vitamin supplementation in dialysis patients, particularly focusing on vitamin C, folate, and thiamine 1.