Nutrition Therapy as an Intervention for Metabolic Acidosis

Nephology providers are used to looking at multiple ways to preserve kidney function, such as managing hypertension and blood sugar levels and using medications to reduce proteinuria and ameliorate cardiovascular problems. For many patients, however, kidney function continues to deteriorate and progress to kidney failure. This could be due to modifiable risk factors that clinicians fail to identify and address. Metabolic acidosis is one of them.

Metabolic acidosis, defined as serum total CO2 concentration less than 22 mmol/L, is estimated to be present in about 27.6% of those with CKD stage 4 and 46.4% of those with stage 5 CKD.1 Metabolic acidosis is associated with poor outcomes in those with CKD, such as bone demineralization, muscle wasting, hormone imbalance, hyperkalemia, failure to thrive, malnutrition, increased risk of falls or fractures, and increased progression of CKD.2,3 Despite this, it is estimated that only 17% of patients receive treatment for metabolic acidosis.4 We can only speculate as to the reasons why there is a low treatment rate, but what we do know is that there are clear targets and interventions for correcting metabolic acidosis.

The KDOQI (Kidney Disease Outcomes Quality Initiative program) guidelines recommend a serum bicarbonate level between 24-26mmol/L.5 Sodium bicarbonate is a common and effective treatment for metabolic acidosis, but there are nutrition interventions that may be more appropriate for some patients or may be used successfully in addition to the sodium bicarbonate.

Multiple studies show that reducing net endogenous acid production (NEAP) can help to improve or correct metabolic acidosis.2,5 Dietary components such as phosphorus and protein are acid-forming in the body, whereas potassium, calcium, and magnesium are more alkalizing.2 Following a low-protein diet or a diet richer in plant proteins naturally reduces the amount of phosphorus and protein, thus reducing NEAP. Although without careful planning, these diets can still be low in potassium, magnesium, and calcium, which can deplete the body's stores. Highly motivated patients can keep electronic food logs that can estimate mineral intake and a diet's potential renal-acid load. A renal dietitian can review these logs to help the patient make food choices that support a lower acid load as well as adequate alkalizing minerals. In some cases, supplements may be appropriate to ensure adequate nutrition and good food quality of life because magnesium and calcium from plant sources are not as well absorbed.

While all these approaches may not be the perfect option for every patient, a survey of CKD patients found that 43% of patients felt that they were capable of making lifestyle changes to reduce complications of CKD and 32% of patients indicated that they would be interested in being referred to see a dietitian.6 The dietitian can work with the patient individually to assess the best way to help them make changes. The key is for the patient to know that they have options to make diet changes or to see a dietitian to slow the progression of their kidney disease.

Research indicates that correcting metabolic acidosis through dietary changes can provide a multitude of benefits: increased insulin sensitivity, improved muscle mass growth, increased protein reserves, slow progression of kidney disease, improve lipid profiles, reduced inflammation, improve blood pressure, reduce pill burden from sodium bicarbonate, and keep the diet more liberal.2,5,7,8

Correcting metabolic acidosis is another tool for providers to use in helping to slow the progression of kidney disease. Including dietary changes (and dietitians) as an intervention for metabolic acidosis provides additional benefits that can support the patient's health on multiple levels.

Lindsey Zirker MS, RD, CSR is a renal dietitian and Director of Clinical Services for the Kidney Nutrition Institute in Titusville, Florida. She specializes in autoimmune kidney disease and advanced practice medical nutrition therapy for people with kidney disease.

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