Vitamins in dialysis: who, when and how much?

Despite the significant technical evolution of the blood purification methods, cardiovascular morbidity and mortality in dialysis patients is still several times higher than that observed in the general population. Vitamins are playing a crucial role in multiple key metabolic pathways. Due to multiple factors, dialysis patients present very often hypo- or hypervitaminosis for a broad range of vitamins. Dialysis in the context of renal replacement therapy is associated with a non-physiological potassium-sparing dietetic regime. Additionally, there is a non-selective intradialytic loss of micro- and macronutrients, deranged intracellular kinetics and gastrointestinal malabsorption due to uratemia. Frequent treatment with antibiotics due to infections associated with the acquired uremia-related immunosuppression may derange the vitamin-producing intestinal microflora. Certain agents prescribed in the context of renal failure or other conditions may reduce the absorption of vitamins from the gastrointestinal tract. These factors may deplete a dialysis patient from vitamins, especially the ones with antioxidant activity that may be associated with cardioprotective properties. In other cases, vitamins metabolized and excreted by the kidneys may be accumulated and exert toxic effects. The scope of this paper is to describe the main issues on vitamin therapy in dialysis patients in view of the ever contradictory opinions and practices.