Dietary interventions may increase health-related quality of life, estimated glomerular filtration rate (eGFR), and serum albumin in patients with chronic kidney disease (CKD), however the effects on mortality, cardiovascular (CV) events and end stage kidney disease (ESKD) remain uncertain. The findings come from a new review of randomized trials published in the Cochrane Database of Systemic Reviews.

The authors searched the Cochrane Kidney and Transplant Specialized Register for randomized controlled trials (RCTs) or quasi-randomized RCTs investigating dietary interventions versus lifestyle advice, or standard care to assess three primary outcomes in CKD patients: the risk of advanced renal disease or death and quality of life.

A total of 17 studies were included in the analysis (n=1,639). Eleven of the studies (n=900) evaluated dietary counseling with or without lifestyle advice, while dietary patterns were evaluated in six studies, these included one study (n=191) of carbohydrate-restricted low-iron, polyphenol enriched diet; two studies (n=181) of increased fruit and vegetable intake; two studies (n=355) of a Mediterranean diet; and one study (n=12) of a high protein/low carbohydrate diet.  

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Results showed that dietary interventions reduced systolic blood pressure (BP) (3 studies, n=167: MD –9.26mmHg, 95% CI: –13.48 to –5.04; I2 = 80%) and diastolic BP (2 studies, n=95: MD –8.95, 95% CI: –10.69 to –7.21; I2 = 0%) compared to a control diet. Additionally, dietary interventions were associated with a higher eGFR (5 studies, n=219: SMD 1.08; 95% CI: 0.26 to 1.97; I2 = 88%) and serum albumin levels (6 studies, n=541: MD 0.16 g/dL, 95% CI: 0.07 to 0.24; I2 = 26%). The Mediterranean diet was found to be associated with reduced serum LDL cholesterol levels (1 study, n-40: MD –1.00 mmol/L, 95% CI –1.56 to –0.44). Based on these studies, it would appear that dietary changes could prevent 1 in every 3,000 people treated for 1 year avoid ESKD, however the certainty in this effect was very low. 

The researchers noted how none of the studies were designed to measure all-cause mortality or cardiovascular events, leaving the effects of such dietary interventions unknown. Given that dietary changes are regularly recommended to those with CKD, the authors of this study assert that pragmatic large-scale RCTs are required to test the effects of dietary interventions on patient outcomes.

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