Patients with chronic kidney disease should consider a diet with a higher proportion of protein from plant sources — such as tofu and beans — to improve their health and lower their mortality risk, according to a study titled “The Associations of Plant Protein Intake With All-Cause Mortality in CKD,” published in the American Journal of Kidney Diseases.
Because high protein intake might accelerate CKD progression, the current national recommendations for daily dietary protein intake are 0.60 grams of protein per kilogram of body weight for people with CKD, and 1.2 grams of protein per kilogram for clinically stable maintenance hemodialysis patients.
To test the hypothesis that at a given total protein intake, a higher proportion of dietary protein from plant sources is associated with lower risk for mortality in CKD, Xiaorui Chen and colleagues examined the association between plant protein intake and all-cause mortality in 14,866 adults (age 20 or older) with estimated Glomerular filtration rates (eGFRs) < 150 mL/min/1.73 m2 (CKD is defined as either kidney damage or GFR <60mL/min/1.73 m2 for >3 months).
A higher proportion of protein from plant sources was found to be associated with lower mortality in CKD patients. “In this study, we found every 33% increase in the plant to total protein ratio was associated with a statistically significant decreased risk of death in those with CKD,” Srinivasan Beddhu, MD, a nephrologist with University of Utah Health Care, said in a recent news release. “Our research indicates that plant-based proteins could play an important role in improving the health outcomes for people with decreased kidney function.”
While the effects of adding plant protein to daily diets are clear, the reasons are less certain. One theory is that plant proteins lower the production of uremic toxins. “These toxins have been implicated in the progression of CKD,” Dr. Beddhu said. “They can also contribute to cardiovascular disease, and death in patients with kidney disease.”
Another possible explanation relates to the levels of phosphorus in the body. When kidneys are functioning normally, they are able to remove phosphorous in the blood. But the kidneys of CKD patients cannot remove the mineral, which can lead to leaching of calcium from the bones and calcium deposits in organs.
“In animal protein sources the absorption rate of phosphorus is higher,” said Dr. Chen, MS, a study co-author and graduate research assistant at the University of Utah School of Medicine. “However, in plant proteins there is a low bioavailability of phosphorus, so a diet high in plant protein for patients with CKD may also lower body phosphorus burden.”
A needed next step is clinical testing of this finding in CKD patients, the researchers said. “Dietary interventions, such as increasing plant protein intake, may have an effect on slowing down the progression of kidney disease,” said Dr. Beddhu. “But this needs to be tested in randomized controlled trials.”