Diet may contribute to metabolic acidosis in renal transplant recipients (RTRs), according to investigators.

In a study of 707 (RTRs), Else van den Berg, MD, of University Medical Center Groningen in Groningen, the Netherlands, and colleagues found that patients with high intake of animal protein, such as from meat, fish, and fish, and low intake of fruits and vegetables had significantly lower serum bicarbonate and serum pH.

Dr. van den Berg and her colleagues explained that many RTRs have metabolic acidosis, which may adversely impact cardiometabolic processes, such as blood pressure (BP) and insulin resistance, and interfere with the proper functioning of multiple tissues.

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“Modification of the diet by increasing fruit and vegetable intake and decreasing intake of animal protein might improve acid-base balances in RTRs,” the authors concluded in an online report in the Clinical Journal of the American Society of Nephrology.

The researchers assessed metabolic acid load by measuring 24-hour urinary net acid excretion (NAE). They defined acidosis as a serum bicarbonate level below 24 mmol/L. Overall, acidosis was present in 31% of subjects.

After adjusting for age, gender, body surface area, medication use, estimated glomerular filtration rate, time since transplantation, and smoking behavior, NAE was inversely associated with serum bicarbonate and serum pH. NAE was positively associated with acidosis, but was not associated with insulin resistance and high BP.

The researchers observed that their findings, if confirmed by prospective and interventional studies, might have implications for clinical practice. Acidosis is highly prevalent among RTRs, they noted, so venous blood gas analysis should be performed occasionally because it provides important information on acid-base status relatively easily, they noted. “If acidosis is confirmed, attention should be paid not only to known risk factors such as graft function but also to dietary habits,” they stated.

On the basis of their results, the investigators reported, daily enrichment of the diet with 100 grams of vegetables and 100 grams of fruits and elimination of 50 grams of meat and 20 grams of cheese would decrease NAE by 15 mEq/day and serum bicarbonate levels would ris by about 0.5 mmol/L.

Study strengths included a large sample size and the use of 24-hour urine samples, which allowed direct measurement of NAE as a marker of metabolic acid load as well as estimation of dietary acid load based on dietary recall. Study limitations included its observational and cross-section design, which does not allow for proving causality.