Nutrition and Chronic Kidney Disease

Denis Fouque; Solenne Pelletier; Denise Mafra; Philippe Chauveau

Disclosures

Kidney Int. 2011;80(4):348-357. 

In This Article

Increasing Protein Intake in Dialysis: The Phosphate Paradigm

If there is no clear nutritional advantage to increase protein intake, is there a metabolic risk to do so? This question arises as protein is linked to phosphate in a strong and accurate relationship: 1 g protein brings 13–15 mg phosphate, of which 30–70% is absorbed through the intestinal lumen. Thus, a 80 kg-patient eating 90 g protein/day may absorb 600–700 mg phosphate daily, which results in a net balance of 1200–1400 mg every other day, an amount that cannot be eliminated through dialysis as a single regular hemodialysis session can only clear 500–600 mg phosphate every other day and 1-day peritoneal dialysis clears ~300 mg phosphate. However, this theoretical calculation is not fully confirmed by clinical observation. Indeed, in a randomized controlled trial, Kloppenburg et al.[75] tested, during 40 weeks twice, two different levels of protein intake (0.94 vs 1.15 g protein/kg/day) that did not result in a variation of serum phosphate (1.89 vs 1.88 mmol/l, respectively, P=nonsignificant), despite a difference in protein intake of 20 g and phosphate intake of 250 mg/day.[75] In a subsequent report, Shinaberger et al.[82] showed that, in more than 50,000 maintenance hemodialysis patients, serum phosphate slightly increased from 5.8 to 6.3 mg/dl when patients' normalized protein nitrogen appearance increase from 1.0 to 1.4 g/kg/day (Figure 2, top). However and more importantly when analyzing patients' survival, the more they ate protein, the more they survived, until reaching a protein intake of 1.4 g/kg/day or above (Figure 2, bottom).[82] In a post hoc analysis of the HEMO study, Lynch et al.[83] also reported that the patients who received no prescribed dietary phosphate restriction had the best survival. In a current follow-up of more than 3000 maintenance hemodialysis patients in France, survival at 30 month was best for the highest protein intakes, without a trend for a J-curve (Figure 1).[76] Taken together, these recent studies indicate that the optimal protein intake in maintenance hemodialysis, based on nPNA, should be targeted from 1.0 to 1.4 g/kg/day. There is no such survival data based on protein intake in peritoneal dialysis patients.

Figure 2.

The phosphate and protein intake paradigm. Mortality decreases when protein intake increases up to 1.4 g/kg/day (lower panel), despite a slight increase in serum phosphate (upper panel; from Shinaberger et al.,82 with the authorization of the American Society of Nutrition). nPNA, normalized protein nitrogen appearance.

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