Vitamin C supplementation in dialysis patients: Benefits and risks

Abstract

Foods that are the main sources of vitamin C are often restricted or needed to be avoided in potassium restricted diets in dialysis patients. Inadequate intake and dialysis losses can result in ascorbate deficiency. Serious vitamin C deficiency seen in many patients may also contribute to poor oral health, chronic fatigue and some comorbidities including cardiovascular and neurological dysfunction. Therefore, a daily vitamin C supplement of 30-90 mg is recommended according to the guidelines on nutrition. However, vitamin C is also used as an adjuvant therapy besides nutritional requirement. The recent accumulating evidences show that vitamin C improves the management of anemia in dialysis patients. Erythropoietin stimulating agent (ESA) hyporesponsive anemia in HD patients most commonly results from iron deficiency, the contributory role of chronic inflammation and OS in its pathogenesis is poorly understood. It also represents, in a great majority of HD patients, the effect of malnutrition-inflammation complex syndrome. The impact of low vitamin C levels and concurrent inflammation causes a large amount of iron to be stored, with relatively inefficient utilization for erythropoiesis, and inflammation has a very similar effect. Research strategies to improve vitamin C status and to decrease inflammation can lead to better utilization of iron stores and enhance the response to ESAs treatment in chronic renal disease patients with functional iron deficiency, and could have parallel benefits for the long-term health of patients on HD. However, potential toxicological effects of usage of large doses of parenteral vitamin C precludes a recommendation for routine clinical use, including the risk of oxalate deposition and the possible risk of development of kidney stones, and the pro-oxidant effect due to an increased formation of vitamin C radicals. In this article, we briefly review vitamin C status in uremic patients, clinical outcome of ascorbate deficiency and its traditional supplementation approaches together with new treatment strategies under development, focusing on its possible disadvantages. © 2011 by Nova Science Publishers, Inc. All rights reserved.