Is the Juice Worth the Squeeze? Vitamin C Supplementation in Hemodialysis Patients: A Systematic Review

<b>Background:</b> Patients undergoing hemodialysis commonly exhibit deficiencies in water-soluble vitamins, primarily as a result of inadequate dietary intake and loss into the dialysate. Given the essential role of vitamin C in numerous metabolic pathways, routine supplementation has been proposed as a potentially beneficial intervention in this population. <b>Aim:</b> We aimed to evaluate the current evidence on vitamin C supplementation in patients undergoing hemodialysis, with particular attention to clinical conditions associated with renal replacement therapy, including anemia, chronic inflammation, restless legs syndrome (RLS), and secondary hyperparathyroidism. <b>Methods:</b> This systematic review was conducted in accordance with PRISMA guidelines. The MEDLINE (via PubMed) and EMBASE databases were searched. The initial search yielded 844 articles, of which 37 studies met the inclusion criteria for this review. <b>Results:</b> Evidence indicates that hemodialysis patients exhibit vitamin C deficiency, both in dietary intake and in plasma or serum concentrations. Despite its intrinsic antioxidant properties and proposed anti-inflammatory effects, vitamin C supplementation has demonstrated inconsistent effects on inflammatory markers. Most clinical studies support a beneficial role of vitamin C supplementation in functional iron deficiency and in alleviating symptoms of RLS within this population. <b>Conclusions</b>: Evidence on vitamin C supplementation for functional iron deficiency and RLS suggests that it might be an effective therapeutic approach. However, despite low serum vitamin C level in hemodialysis patients, current data does not justify the routine use of vitamin C in the hemodialyzed population for other comorbidities, including chronic inflammation and secondary hyperparathyroidism. Further high-quality studies are required to establish the broader clinical utility of targeted vitamin C supplementation.