Effect of fruit and vegetable intake on the progression of kidney failure in adults with chronic kidney disease: a systematic review

Abstract

Background: Dietary intervention has been a significant part of chronic kidney disease (CKD) treatment with the emphasis on reducing protein, sodium, phosphorus, and potassium intake, limiting fruit and vegetable consumption. These dietary recommendations are very restrictive and difficult to comply with. Recent evidence shows that fruit and vegetable intake might be a cost-effective and acceptable management option for patients with CKD and that overall healthy dietary patterns rich in fruit and vegetables may improve clinical outcomes of these patients. The aim of the current study was therefore to perform a systematic review that investigated the effect of various fruit and vegetables on specified clinical outcomes of patients with CKD. Methods: Two systematic reviews were performed. The first aimed to investigate the effect of fruit and vegetable intake on clinical outcomes of patients with CKD, especially on estimated Glomerular Filtration Rate (eGFR). Randomised controlled trials (RCTs) of the effect of fruit and vegetable intake on blood pressure, metabolic acidosis and eGFR in adult patients with CKD (eGFR <60 ml/min/1.73m2) published before April 2019 were included. Control groups received usual care. The aim of the second narrative systematic review was to investigate the effect of dietary patterns on clinical outcomes of patients with CKD, especially the progression of kidney failure. Cohort studies with an adult population with CKD not receiving dialysis, published before July 2019, were included. The searches for both studies were systematically performed on EBSCO Host, Google Scholar, MedLine, Pubmed, Science Direct, Scopus and The Web of Science on studies and The Cochrane Central Register of Controlled Trials using keywords and MeSh terms. Results: Two studies with a total of 143 participants were included in the systematic review of RCTs. The eGFR of the fruit and vegetable group in the first study was the same as that of the group receiving oral sodium bicarbonate (NaHCO3) after one year (Goraya et al., 2013). The eGFR was also significantly higher in the fruit and vegetable group when compared with usual care. The included studies found a significant reduction in body weight, systolic blood pressure and potential renal acid load (PRAL) when compared to baseline and to control group, and significant improvement in plasma total carbon dioxide (TCO2) in the fruit and vegetable group when compared to baseline. Fruit and vegetable intake had no effect on plasma potassium when compared to baseline and/or to the control group in both the studies included. Five observational studies with a total of 8 649 participants were included in the narrative systematic review of cohort studies. Four of the included studies found that a higher plant-based dietary pattern and intake of fruit and vegetable reduce all-cause mortality in patients with CKD when compared with the lowest quintile intake. Conclusion: Fruit and vegetables are just as effective in delaying the progression of kidney failure as NaHCO3 in CKD patients with metabolic acidosis, without producing hyperkalaemia. Dietary patterns rich in fruit and vegetables are associated with lower mortality rates in patients with CKD, but further well-designed trials with clearly defined portion sizes and quantities of fruit and vegetable intake or dietary pattern are needed.