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Very low-protein diet provides no improvement in risk of CKD progression, may increase risk of mortality long-term, study data suggest

Friday, October 31 2008 | Comments

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What's This? Assignment to a very low-protein diet does not appear to delay progression of chronic kidney disease (CKD) to kidney failure in long-term analysis, but it may increase the risk of mortality, according to long-term results from study B of the MDRD study.

"There are limited data for long-term effects of very low-protein diets on clinical outcomes in patients with nondiabetic CKD; however, dietary protein restriction remains a therapeutic consideration in these patients," the authors of the study wrote.

To examine the long-term effects of a very low-protein diet in patients with CKD, researchers compared outcomes among 255 participants in the MDRD study who had predominantly stage 4 nondiabetic CKD and were randomized to either a low-protein diet (0.58 g/kg/day) or a very low-protein diet (0.28 g/kg/d) supplemented with a mixture of essential keto acids and amino acids (0.28 g/kg/d). The primary endpoint was a composite of kidney failure and all-cause mortality.

Overall, during long-term follow-up, 227 patients (89%) developed kidney failure, 79 (30.9%) died, and 244 (95.7%) reached the composite endpoint of kidney failure or death.

Kidney failure occurred in 117 patients (90.7%) in the low-protein group compared with 110 patients (87.3%) in the very low-protein group; 30 patients (23.3%) in the low-protein group died compared with 49 patients (38.9%) in the very low-protein group, and 124 patients (96.1%) in the low-protein group reached the composite primary endpoint compared with 120 patients (95.2%) in the very low-protein group.

These rates translated to a similar risk of kidney failure or the composite primary endpoint between groups, but a significant 82% greater risk of all-cause mortality among patients in the very low-protein group than in the low-protein group in unadjusted analysis (P=.01).

In additional analyses, the risk of mortality before kidney failure was similar between groups. However, mortality after kidney failure was more than 2-fold more likely among patients randomized to the very low-protein diet than among those randomized to the low-protein diet (HR, 2.43; 95% CI, 1.33-4.43).

"In summary, assignment to a very low-protein diet increased the risk of death in long-term follow-up of the MDRD study, but had no impact on delaying the progression to kidney failure and no relationship with a composite outcome of kidney failure and death," the authors concluded.

"Although very low-protein diets generally are not recommended, we believe these findings are clinically relevant given the continued interest in the use of dietary protein restriction as an intervention to delay progression of kidney disease," they continued.

These findings were published online ahead of print by the American Journal of Kidney Diseases by Menon V, et al.

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