Dietary-based Approaches to Treating Metabolic Acidosis in Patients with Chronic Kidney Disease

A diet rich in highly alkaline fruits and vegetables helps reduce a marker of metabolic acidosis and preserve kidney function in patients with chronic kidney disease.

Fruits and vegetables can be an important healthy addition to the diet of patients with kidney disease and subtract less from the wallet than might be expected, according a researcher who presented study results during Kidney Week 2012, a conference of the American Society of Nephrology held in San Diego.

A study, conducted by Nimrit Goraya, MD, of Texas A&M College of Medicine, sought to learn more about whether adding fruits and vegetables to their diet improves the health of patients who have chronic kidney disease.

Patients in the study were given either bicarbonate or affordable fruits and vegetables that were highly alkaline, to test whether this would slow the rate of decline in kidney function in patients who have moderately reduced function and hypertension-associated kidney disease, Goraya said.

Alkali therapy is often used to treat kidney patients who have too much acid in the body, also known as severe metabolic acidosis, but treatment guidelines are in a “gray zone” for those whose condition is not severe, Goraya said. Study participants all had metabolic acidosis that was not severe enough to recommend alkali treatment under current guidelines, she said.

The study involved 108 people who had moderately reduced kidney function and high urine protein excretion, a known marker of kidney disease.They were randomized to three groups, to receive bicarbonate, fruits and vegetables, or to a control group with nothing given for dietary acid reduction. ACE inhibitors were given to patients to control blood pressure. All were followed and had lab work monitored for three years.

Most of the patients were living at the poverty line, with an average income of roughly $1,400 a month; Goraya said. Participants in the food group as well as their families were given extra fruit and vegetables that were distributed through local food banks and churches. They were asked to use food diaries to write down whatever they ate for three-day periods in order to track dietary acid consumption.

“We didn’t ask them to change their whole diet. We gave them the amount of fruit and vegetables that we had calculated would reduce their potential renal acid load,” said Goraya.

The additional fruits and vegetables included affordable, alkaline-based items like potatoes and raisins and cost about $150 a month for each family. “We’re not asking them to eat very exclusive food from farmers’ markets, but simple foods,” noted Goraya.

At the beginning of the study, systolic blood pressure in all groups was similar and after three years of treatment it decreased in all groups, but was the lowest in the fruits-and-vegetables group, Goraya said. Urinary angiotensinogen, a marker of kidney injury, also decreased among those who were given fruits and vegetables or bicarbonate.

“So again, fruits and vegetables were shown to lower blood pressure in these patients as was also noted by the DASH data,” said Goraya, referencing the Dietary Approaches to Stop Hypertension (DASH), a government-sponsored research initiative that encourages a diet rich in fruits, vegetables, whole grains, and low-fat dairy foods.

Goraya said the crux of the research is to find ways to manage kidney disease by preventing injury before it occurs.