Diet in ESRD and Hemodialysis Patients
The long forgotten salt factor and the benefits of using a 5-g-salt-restricted diet in all ESRD patients
By : Stanley Shaldon and Joerg Vienken
This is a review of the significance of reviving the routine diet management of limited salt intake to 5g per day for ESRD patients undergoing hemodialysis using several studies undertaken by several authors. Two of the latest studies were published in 2004 entitled Dialysis Outcomes Quality Initiatives Guidelines on the problem of cardiovascular disease in ESRD patients (K/DOQI) and the other one published in 2006 by the same learned body (K/DOQI) using 60 references on the use of a salt-restricted diet in the management of ESRD patients undergoing hemodialysis. This revival of this long abandoned treatment policy may be traced from an empirical observation published over 40 years ago on salt restriction to 5g/day on ESRD patients with severe hypertension (Comty and Shaldon, 1964). The findings then was that it took several months to control blood pressure without taking medications for hypertension. The lag phenomenon was independent of the initial decrease in blood pressure related to decreasing extracellular volume and getting an arbitrarily defined dry body weight This means that the delay in the reduction in mean arterial pressure happened several months after stabilizing both the exchangeable sodium and body weight. This lag phenomenon was due to the reduction in peripheral resistance which may be related to the reduction of non-osmotically active sodium that may be attached in the lining of intimal surface of blood vessels( which contains proteoglycans and glycosaminoglycans (Shaldon, 2006; Titze, 2004) . This sodium store takes months to normalize on a 5-g salt intake.
The results of these studies indicate that for ESRD patient on hemodialysis, the survival rate increases not much because of the technical aspects of the therapy but due largely to the adherence on the 5g daily salt intake in the diet. Local high sodium concentration stimulate the release of the gene that is responsible for inducing inflammatory cytokine cycle, MAPK38 (mitogen-activated protein kinase) which result to ADMA (asymmetric dimethyl arginine)-induced increase in peripheral resistance (this is due to reduction in nitric oxide synthesis). The low-salt dietary intake will reverse this whole process and at the same time reverse the production of inflammatory cytokines leading to reduction in blood pressure.
These findings are further reinforced by another randomized study (Cook, et al, 2007) of prehypertensive’ normals (ages of 35 to 55) who were monitored for 10 years with compliance estimated by monthly 24-h urinary sodium determinations. The application of this salt-restricted diet resulted to positive outcome of 25% reduction in cardiovascular morbidity and mortality for the group of patients taking 5g/day salt in their diet as compared to those with a normal unrestricted salt intake in their diet.
This may seem such a simple resolution to a problem such as hypertension but it could mean improved and prolonged survival for ESRD patients undergoing lifetime hemodialysis. However, it is my observation that even this simple management is being overlooked by the patients themselves perhaps due to the fact that many are not cognizant of how to measure and monitor their salt intake on a daily basis. Moreover, people do not relish eating bland foods and are easily tempted to use liberal amount of seasoning and salt in their diet. As observed by the authors, nowadays, there is a tendency to increase salt intake due to the worldwide acceptance of processed foods and instant cooking which contributes to the difficulty of controlling salt in the diet.
1. Kidney Disease Outcomes Quality Initiative (K/DOQI). Clinical practice guidelines on hypertension and antihypertensive agents in chronic kidney disease. Guideline 6: dietary and other therapeutic lifestyle changes in adults. Am J Kidney Dis (2004) 43(Suppl_1):s116.
2. Kidney Disease Outcomes Quality Initiative (K/DOQI10. Clinical practice guidelines for hemodialysis adequacy update 2006. Guideline 5: on control of volume and blood pressure. Am J Kidney Dis (2006) 48(Suppl 1):s33.
3. Comty C, Rottka H, Shaldon S. Blood pressure control in patients with end stage renal disease treated by intermittent haemdialysis. Proc Eur Dial Transplant Assoc (1964) 1:209–213.
4. Shaldon S. Editorial: an explanation for the lag phenomenon in drug-free control of hypertension by dietary salt restriction in patients with chronic kidney disease on hemodialysis. Clin Nephrol (2006) 66:1–2.[ISI][Medline]
5. Titze J, Shakibaie M, Schaffihuber M, et al. Glycosaminoglycan polymerization may enable osmotically inactive Na+ storage in the skin. Am J Physiol Heart Circ Physiol (2004) 287:H203–H208.[Abstract/Free Full Text]
6. Ritz E. Where does some of the ingested sodium chloride hide without exerting osmotic pressure? J Am Soc Nephrol (2006) 17:3–11.[Free Full Text]
7. Cook N, Cutler JA, Obarzanek E, et al. Long term effects of sodium reduction on cardiovascular disease outcomes: observational follow up of the trials of hypertension prevention (TOPH). BMJ (2007) 334:885.[Abstract/Free Full Text]