Don’t ignore vitamin C management in CKD

Vitamin C, like many other nutrients in CKD, has been associated with concerns that elevated levels may cause harm. This is mainly due to the role of vitamin C in the formation of oxalate, which can lead to kidney stones, increase oxalate accumulation in bones and soft tissues, and even lead to kidney stones. may lead to damage. Although it is important to be aware of the potential harms of nutrients, oxalate nephropathy is rare, with an estimated prevalence of 3.6%.¹

Studies have found that 64% of patients undergoing hemodialysis (HD) and peritoneal dialysis (PD) have low vitamin C levels.² Another study found that 52% of people prescribed vitamin C supplements still had low vitamin C levels.³ Reduced vitamin C levels are also associated with increased mortality,^Four endothelial dysfunction, increased oxidative stress, and cardiovascular disease.^Five This suggests that increasing vitamin C intake may play a beneficial role in improving outcomes in CKD patients.

The Kidney Disease Outcomes Quality Initiative (KDOQI) guidelines set the Recommended Dietary Allowance (RDA) for vitamin C at 90% for men with CKD stages 1-5 on dialysis or undergoing kidney treatment. mg/day, and 75 mg/day for women. transplant.⁶ However, the KDOQI guidelines point out that there is limited research to clarify the need for vitamin C at all stages in CKD patients. Therefore, at present, individualized recommendations are the most appropriate clinical approach for vitamin C recommendations for CKD patients.³

Clinicians can consider the following to make individualized vitamin C recommendations:

• Remember that RDA recommendations are only appropriate for healthy individuals. Specifically, they state that alternative recommendations are more appropriate for patients with HD or PD.⁸
• Consider dialysis losses (average 66 mg per HD treatment, 29 mg per PD session). However, some studies have estimated vitamin C losses as high as 300 mg per HD treatment.⁹
• Consider current patient intake (average intake for HD patients was found to be 66 mg/day).^Ten
• Studies have shown both increased and decreased renal reabsorption in CKD.⁹
• CKD patients often have inflammation, anemia, periodontal disease, and secondary hyperparathyroidism, which may increase their need for vitamin C.^Four
• Consider the patient’s history of kidney stones or other oxalate-related problems such as gastric bypass or fat indigestion.¹¹
• If a deficiency is found, doses above the RDA are required to replenish vitamin C. Also keep in mind that doses above 500mg are not usually absorbed, so dosage adjustments may be necessary.¹²

Dosages from research to guide clinicians in making recommendations:

Treatment for deficiency (in people without CKD) starts with high concentrations and then gradually reduces them.¹³

• Take 1-2g/day divided into 2-3 days.
  • 500mg divided into 7 days
  • Monitor symptoms for resolution. Some people may have other conditions that require higher doses of vitamin C or require gut health support to optimize absorption.

Concerns regarding oxalate/kidney stones:^{6, 11, 12}

• Doses above 500 mg/day may increase serum oxalate levels
  • Evaluate fat digestion and calcium intake to reduce oxalate absorption.

Although the possibility of oxalate nephropathy should not be ignored, fear of it may increase the disease burden for patients. Clinicians can stay up to date with guidelines and updates on vitamin C and CKD, and help patients avoid nutrient fears by having trained renal nutritionists provide individualized needs assessments and dietary and supplement recommendations. We can help you focus on nourishing your body instead of on your body. Many nutritional recommendations related to CKD focus on the harm of elevated levels, overshadowing the effects of too little. However, as personalized assessment and care becomes more prevalent, clinicians will have better clinical judgment and patients will be able to reap the myriad benefits of adequate nutrition.

Lindsey Zilker, MS, RD is a renal nutritionist at the Renal Nutrition Institute in Titusville, Florida. She specializes in autoimmune kidney disease and advanced medical nutritional therapy for kidney disease patients.