Table 2.

A synthesis of the present panorama on diet and dialysis through four open questions and four paradoxes.

The Questions	Pros	Cons	Comments
Are the nutritional requirements usually cited (calories: 30–35 kcal/kg; proteins > 1.2 g/kg) still relevant?	International standard followed for more than 40 years	The requirements were assessed in a different dialysis population, and may not be relevant to the present one; they do not consider the changes in the indications given to the overall population	There is a need for a re-assessment of the requirements of elderly dialysis patients
Are the present standards of “adequate nutrition” applicable to intensive dialysis schedules, and to haemodiafiltration?	Simple markers such as albumin level make it possible to compare results, and are robust enough to maintain a constant predictive value	Sensibility may be lower in non conventional dialysis techniques, and can be affected by albumin losses in haemodiafiltration	None of the proposed evaluations of malnutrition is clearly superior or self-standing; results of studies depend in part on the definition-diagnoses chosen
Processed and preserved food may be significantly different from untreated food. What are we eating?	Nutritional approaches have to be simple and basing them on quantity and quality may not be feasible	Processed foods may be rich in rapidly absorbable phosphate and potassium	Not acknowledging the importance of additives in processed and preserved foods can lead to unnecessary restrictions
Is malnutrition a single disease or the result of several diseases?	The clinical signs of malnutrition are universal and do not depend on pathogenesis	If malnutrition is not linked to poor intake but to poor clinical conditions, itwill not respond to therapy	Differentiation may allow setting attainable goals according to the individualpatient’s comorbidity
The paradoxes	The “logic” (overall population or general data in the dialysis population)	The finding (in the dialysis population or in specific dialysis populations)	Comments
Obesity and survival	Obesity is associated with lower survival in the overall population	Obesity is associated with higher survival in dialysis patients; losing weight is associated with higher mortality on dialysis	Obesity is often a contraindication for kidney transplantation
High protein intake and phosphate control	A high protein diet is indicated after dialysis start	Reduction of phosphate intake is not compatible with a high-protein diet	Plant derived phosphate may be less well absorbed; acidosis induced by catabolism is often a missing element in hyperphosphatemia
Albumin level, Kt/V and survival	Low serum albumin and low dialysis efficiency are associated with reduced survival	In haemodiafiltration, high efficiency is coupled with significant albumin losses	Albumin losses are incompletely quantified; nutrition is probably more important than high efficiency in elderly or fragile sarcopenic patients
Potassium and vascular health	Since dialysis patients are at risk for hyperkalemia, potassium is often restricted	Banning plant derived food to avoid hyperkalemia limits consumption of “vascular healthy” food in a high-risk population	Hyperkalemia is still a rare, but possible cause of death