High-Acid Diets May Increase Risk of Kidney Failure in Patients with Chronic Kidney Disease

Small clinical trials have shown that reducing dietary acid load can slow the progression of chronic kidney disease (CKD), but long-term, population-based studies have been lacking. Now, in an analysis of the 1988–1994 National Health and Nutrition Examination Survey (NHANES III), investigators revealed that patients with CKD who consumed high-acid diets were three times more likely to experience ESRD than were patients who consumed low-acid diets. The findings suggest that efforts to improve diet quality at both the population and the individual patient levels could potentially improve CKD outcomes.

Researchers have noted that contemporary Western diets are becoming more acid based. Meat, fish, cheese, grain products, and rice are relatively strong net acidifying foods, whereas fruit (apples, peaches, and raisins), legumes, vegetables (spinach and cauliflower), and potatoes are relatively strong net alkalinizing foods. The mechanisms by which acid-inducing diets affect kidney health are unknown, but tubular toxicity of elevated ammonium concentrations and activation of the renin-angiotensin system may be involved.

“Nutrition is emerging to the forefront as a major modifiable determinant of disease, with scientific evidence increasingly supporting the view that alterations in diet have important effects on health throughout life,” said Tanushree Banerjee, PhD, a researcher at the University of California–San Francisco and the lead author of the study published by the Journal of the American Society of Nephrology.

Banerjee and her colleagues analyzed information on 1486 adults who had CKD and were followed up for a median of 14.2 years. The investigators estimated the dietary acid load from 24-hour dietary recall data using previously validated equations.

In total, ESRD developed in 311 (20.9 percent) of the study participants. After adjustment for potential confounding factors, higher levels of dietary acid load were associated with increased risks of ESRD, with a 3-fold increased risk for the highest tertile and a 1.8-fold increased risk for the middle tertile compared with the lowest tertile. Even for a shorter follow-up of less than 6 years, the investigators noted a much greater risk of ESRD with high dietary acid load.

The risk of ESRD that was associated with dietary acid load increased as kidney function decreased. Also, high dietary acid load was strongly associated with ESRD risk among individuals with albuminuria of 30 mg/g or above compared with those with normal albuminuria below 30 mg/g. This suggests that higher dietary acid load may lead to kidney injury, which may portend progression to ESRD.

“Patients with CKD may want to pay more attention to diet consumption of acid-rich foods to reduce progression to kidney failure, in addition to employing recommended guidelines such as taking kidney-sparing medication and avoiding kidney toxins,” said Banerjee. “The high costs and suboptimal quality of life that dialysis treatments bring may be avoided by adopting a more healthy diet that is rich in fruits and vegetables.”

Muhammad Magdi Yaqoob, MD, PhD, FRCP, who was not involved with the study and is a professor and consultant in nephrology at the University of London & Barts Health National Health Service Trust, in the United Kingdom, noted that the research adds to the growing body of experimental and clinical evidence suggesting that acidosis can be a modifiable risk factor in the progression of CKD, but that studies with hard outcomes are needed to determine the safety and benefits of reducing dietary acid load in patients. “I strongly recommend a definitive multicenter randomized controlled clinical trial of a low dietary acid load diet compared with a normal diet in patients with CKD stages 3b–5, with progression to renal failure as a primary endpoint,” he said. “Secondary endpoints should include quality of life, mineral and bone disorder, and protein energy wasting.”

Study coauthors include Deidra Crews, MD, Donald Wesson, MD, Anca Tilea, MS, Rajiv Saran, MD, Nilka Ríos Burrows, MPH, Desmond Williams, MD, and Neil Powe, MD.

Disclosures: The authors reported no financial disclosures.

The article, entitled “High dietary acid load predicts ESRD among adults with CKD,” is available at http://jasn.asnjournals.org/content/early/2015/02/11/ASN.2014040332.