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Researchers say a diet with plenty of fruits and vegetables doesn’t appear to increase potassium levels in people with chronic kidney disease. Marc Tran/Stocksy
  • Researchers report that eating more vegetables and fruits is associated with a lower risk of death in people with chronic kidney disease.
  • Doctors sometimes advise individuals with advanced chronic kidney disease (CKD) to eat a low-potassium diet because their kidneys struggle to process it, leading to high levels of potassium in the blood.
  • In this study, researchers found similar baseline serum potassium levels stratified by CKD stage across different groups compiled by frequency of intake of vegetables and fruits.
  • The researchers say this suggests that eating vegetables and fruits every day may not be associated with an increased level of serum potassium.

Individuals with chronic kidney disease (CKD) face a gradual loss of kidney function.

More than 1 in 7 adults in the United States have CKD, according to the National Institute of Diabetes and Digestive and Kidney Diseases.

Since there are often no symptoms in its early stages, CKD often goes undetected until the condition is advanced.

When kidneys are damaged they sometimes allow potassium to build up in the blood. Hyperkalemia is the term for high potassium levels.

In one study, researchers found more than one-half of the participants, all of whom had advanced CKD, had potassium levels above the conventional limit. As CKD patients lose kidney function, medical practitioners sometimes tell them to stick to foods lower in potassium.

A study of people in Japan with and without CKD found a lower intake of fruits and vegetables to be associated with a higher risk of death.

A paper about the work was published in the Journal of Renal Nutrition.

Public health officials often sing the praises of consuming plants.

Eating fruits and vegetables is associated with a reduced risk of heart disease, cancer, and all-cause mortality.

Advanced CKD patients sometimes find themselves consuming fewer meals with vegetables and fruits because of concerns about sticking to a diet low in potassium, the researchers write in their paper.

The researchers were interested in a 2019 systematic review of observational studies that showed fruit and vegetable intake to be low among participants receiving hemodialysis and that higher consumption is associated with lower all-cause and non-cardiovascular death.

Specifically, the researchers reported that increasing vegetable and fruit intake to about 17 servings per week was associated with a 20% lower risk of all-cause mortality compared to an intake of two servings per week.

Since Asian diets are often higher in fruits and vegetables, the researchers decided to conduct their study of participants with and without CKD in a Japanese hospital.

This study involved more than 2,000 adults age 20 or older who visited one of several outpatient departments on the only hospital on Sado Island in Japan between 2008 and 2016.

To be included, participants needed a record of baseline serum creatinine and urinalysis measurements as well as information about vegetable and fruit intake. They also had at least one follow-up assessment.

The mean age of participants was 69. Of the participants, 55% were men and 64% had hypertension (high blood pressure) and 39% had diabetes.

Participants were grouped according to how they answered questions about whether they ate fruits and vegetables “never or rarely,” “sometimes,” or “every day.” About half of participants reported eating fruits and vegetables every day and 15% reported never eating fruits and vegetables.

These participants were divided into groups of those without CKD, those with CKD who were not dialysis-dependent, and hemodialysis patients. Of the participants, 45% were patients with non-dialysis-dependent CKD and 7% were on hemodialysis.

More than half of the participants with non-dialysis-dependent CKD reported consuming fruits and vegetables every day. Only 28% of patients on hemodialysis reported daily consumption of fruits and vegetables.

During a median follow-up of 5.7 years, 561 deaths were observed. Researchers obtained information about whether or not the participants had died using medical records, obituaries, and reports from family members or friends.

Researchers adjusted the analysis for factors such as gender and age, demographics (including whether or not participants smoked and body mass index), and various co-morbidities.

Compared to participants who ate vegetables and fruits every day, participants who sometimes ate these foods had 25% higher risk of dying from any cause.

Those who never or rarely consumed vegetables and fruits had a 60% higher risk of dying from any cause.

Baseline data showed that serum potassium levels stratified by CKD stage were similar across all vegetable and fruit intake frequency groups. This suggests, the researchers wrote in their paper “that vegetable and fruit intake frequency is not associated with serum potassium levels even in patients with advanced CKD.”

“The association was similar regardless of CKD status, with no effect modification by CKD status,” the researchers wrote. “Our results suggest that eating both vegetables and fruits every day may not be associated with increased serum potassium levels and that it may reduce rather than increase all-cause mortality in patients with CKD including those on [hemodialysis]”

The researchers cautioned in their paper that participants with advanced CKD may have consumed fruits and vegetables that contained less potassium or soaked or boiled foods before eating them to remove potassium — a common recommendation made to Japanese CKD patients.

“However, accumulating evidence suggests that dietary potassium levels are not associated with serum potassium levels or hyperkalemia,” they wrote.

Dr. Anjay Rastogi, a professor and clinical chief of nephrology at the David Geffen School of Medicine at the University of California Los Angeles, told Medical News Today that the study was “thought-provoking” but said it had several limitations.

In Japan, he pointed out, much of the population eats more fruits and vegetables than in the United States.

“Is it even applicable to a country like the U.S.?” Rastogi asked.

Additionally, Rastogi had concerns that the participants only reported about their fruit and vegetable consumption on one occasion and may have only provided labs from one date.

“There were a lot of details that were not there,” he said.

Rastogi said he feels that people with advanced CKD need to eat a diet low in potassium.

“It’s a very important mineral element in our body, but obviously in patients with kidney disease who have hyperkalemia, it can wreak havoc,” Dr. Rastogi said of potassium. “It can cause cardiac arrest.”

It’s important for people with CKD to work with a registered dietician, Rastogi said, so that they lower their potassium and continue eating fruits and vegetables.

For people who can’t lower their potassium through diet, there are new potassium binders on the market to treat hyperkalemia, he noted.

“I am a very big proponent of diet, you know lifestyle changes, for slowing down progression of not just kidney disease, but cardiovascular disease,” Rastogi said. “The number one cause of death in a kidney patient is cardiovascular disease. They both go hand in hand.”

Kristen Carli, a registered dietician and owner of Arizona-based Camelback Nutrition & Wellness, stressed to MNT that patients do not need to eat a diet low in potassium until they reach stage four or five of CKD.

“Before we reach that severity of decrease in kidney function, then we should be encouraging a healthy diet, which of course is plentiful in fruit and veggie intake,” she said.

Dr. Deidra Crews, a professor of medicine in the division of nephrology at the Johns Hopkins University School of Medicine in Maryland, told Medical News Today that health practitioners a lot of times “advise people with chronic kidney disease in ways that are not very nuanced.”

“There are people who have very advanced chronic kidney disease, or even kidney failure, where diets that are high in potassium may pose a problem for them,” she said. “But the overwhelming majority of people who have chronic kidney disease actually have less severe chronic kidney disease. So, if you look at the more than 37 million people in the United States that have chronic kidney disease, most of them have this sort of less severe disease, where the types of dietary practices that are going to help them to not get cardiovascular disease and to live [a long life] are going to be very similar to what we might advise the more general population, which is: eat your fruits and vegetables.”

Studies like this one out of Japan are prompting interest in further research looking at whether diets rich in fruits and vegetables are actually associated with hyperkalemia in people with advanced CKD, Crews said.

Although people with advanced CKD often cannot rid their bodies of potassium through the kidneys, they may be able to do it through “pathways that exist in the gut, in the bowels,” she said.

Crews stressed that since fruits and vegetables often are high in fiber, they may help with that process.