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Greater fruit, vegetable intake associated with lower risk of mortality for patients on hemodialysis
Greater consumption of fruits and vegetables was associated with a reduced risk for all-cause and non-cardiovascular mortality in patients with ESKD on hemodialysis, yet their fruit and vegetable intake continued to be lower than that of the general population, according to a study published in the Clinical Journal of the American Society of Nephrology.
“Emerging evidence suggests that a diet rich in fruit and vegetables may be associated with lower mortality among adults with CKD,” Valeria M. Saglimbene, MScMed, of the Sydney School of Public Health at the University of Sydney in Australia and the Diaverum Medical-Scientific Office in Sweden, and colleagues wrote. “In patients with ESKD treated with hemodialysis, a high consumption of these foods is generally discouraged to prevent hyperkalemia. However, the effects of fruit and vegetables on mortality in this population have not been examined.”
To evaluate the association of fruit and vegetable intake with all-cause cardiovascular and non-cardiovascular mortality in adults undergoing hemodialysis, researchers analyzed data from 8,078 participants (58% men; mean age, 63 years; on hemodialysis for median of 3.6 years) who completed a food frequency questionnaire as part of the Dietary Intake, Death and Hospitalization in Adults with ESKD Treated with Hemodialysis (DIET-HD) study. DIET-HD was a multinational, prospective, cohort study conducted in 11 countries between January 2014 and January 2015 and the food frequency questionnaire asked participants how often they ate fresh fruit and vegetables during the previous year.
Researchers converted responses into average servings per week. Participants were followed up for a median of 2.7 years. During this time, 2,082 deaths occurred. Of these, 954 were cardiovascular.
The questionnaire revealed that respondents consumed a median of eight servings of fruit and vegetables per week and 4% consumed at least four servings per day as recommended in the general population.
Researchers also found that, when compared with the lowest tertile of servings per week (0 to 5.5, median 2), the adjusted HR for the middle (5.6 to 10, median 8) and highest (greater than 10, median 17) tertiles were 0.90 and 0.80 for all-cause mortality, 0.88 and 0.77 for non-cardiovascular mortality and 0.95 and 0.84 for cardiovascular mortality.
“Our findings suggest that well-meaning guidance to limit fruit and vegetable intake to prevent higher dietary potassium load may deprive hemodialysis patients of the potential benefits of these foods,” the researchers wrote. “As the evidentiary basis for dietary fruit and vegetable consumption is currently reliant on non-randomized data, intervention trials of fruit and vegetable intake are needed to support dietary recommendations for hemodialysis patients. Future studies exploring the potential benefits of a whole dietary approach in the hemodialysis setting are also warranted.”
In a related editorial, Ranjani Moorthi, MD, MPH, MS, of the division of nephrology in the department of medicine at Indiana University School of Medicine, wrote: “Inadequate fruit and vegetable intake may be a lifelong habit in some individuals, but the findings from this study demonstrate that it is dramatically lower in those on hemodialysis compared to the general population. As the authors point out, patients undergoing hemodialysis are routinely advised to eat a 2 g potassium/day diet. Patient education materials often include food lists categorizing potassium-containing foods. Given the repeated advice patients on dialysis hear to avoid potassium-containing foods (as well as for years in pre-dialysis CKD clinics), it is plausible that many patients just chose to avoid fruits and vegetables to limit potassium. The inadvertent consequence of this avoidance is that they fail to derive benefits from fruits and vegetables such as the antioxidants, fiber and other benefits. Despite this recommendation, there is actually little data to support that eating fruits and vegetables increases serum potassium. The hope is this excellent cohort study will form the basis of well-designed randomized control trials to test the effect of fruits and vegetables in patients undergoing hemodialysis, so we, as their nephrologists, along with renal dieticians, can provide the details of dietary guidance they deserve.” – by Melissa J. Webb
Disclosures: The authors report no relevant financial disclosures.
Perspective
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In this study, published in the Clinical Journal of the American Society of Nephrology, Saglimbene and colleagues show that dialysis patients who consumed higher amounts of fruits and vegetables had a decreased risk of mortality. The classic renal diet was under inquiry in the study, as well as the evidence linking potassium foods to high serum potassium levels. In an accompanying editorial, Moorthi highlights the radically low intake of fruits and vegetables in the hemodialysis population.
Kidney Disease Outcomes Quality Initiative guidelines for renal nutrition encourage 2,000 mg to 3,000 mg of potassium per day, which may lead patients to avoid many fruits and vegetables. From my standpoint, there has been a disservice to the CKD population in the past as patients were told to avoid many plant-based foods for the risk of elevating potassium. Current education by registered dietitian nutritionists, such as the Renal Practice Group, aims to increase plant-based nutrient-dense food sources and decrease processed foods that are more detrimental to overall health.
Randomized controlled studies are necessary to evaluate potential outcomes of higher fruit and vegetable intake in the CKD population. The western diet is significantly different from that of other nations. Average intakes of fruit and vegetables vary among genders. The direct effect of potassium foods on serum potassium levels and patient outcomes needs to be evaluated. Increases in natural fibers from plant-based diets are likely to promote the excretion of potassium and ought to be considered.
As clinicians, we must evaluate and balance potassium in the diet. Are patients overeating potassium fruits and vegetables or are processed foods more than likely the culprit? Fruits and vegetables have numerous benefits, such as alkalinizing effects against metabolic acidosis, as well as decreasing inflammation, oxidative stress and constipation. The KDOQI nutrition guidelines are currently under review and may provide the reprieve we need to offer guidance that is more specific.
References:
Clegg D, et al. Clin J Am Soc Nephrol. 2019;doi.org/10.2215/CJN.08960718.
Sparks B. Jrnl of Renal Nut. 2017;doi.org/10.1053/j.jrn.2017.12.002.
St-Jules D, et al. Jrnl of Renal Nut. 2016;doi.org/10.1053/j.jrn.2016.02.005.
American Renal Associates
Beverley, Massachusetts