ASN Guidance on Potassium and Phosphorus Additives

For better or worse, food additives can affect the health and nutrition of people with chronic kidney diseases (CKD) more quickly and dramatically than whole foods. Additives are ubiquitous in the US food supply.

To help health care providers and patients become more savvy on what they are consuming, the American Society of Nephrology (ASN) has issued new guidance on potassium and phosphorus additives. We asked workgroup co-chairs Annabel Biruete, PhD, RD, FASN and Csaba P. Kovesdy, MD, FASN to give us an overview of the guidance and how to apply it. Dr Biruete is an assistant professor of nutrition science at Purdue University in West Lafayette, Indiana. Dr Kovesdy is the Fred Hatch professor of medicine and chief of nephrology at The University of Tennessee Health Science Center in Memphis, Tennessee. 

Why did the ASN work group decide to tackle the topic of potassium and phosphorus additives? 

Potassium and phosphorus additives can influence the health of patients with kidney diseases because they are highly bioaccessible. Identifying these additives is difficult and confusing due to incomplete information on food labels and food databases. The ASN continues to actively work to make food labels more accurate and transparent. 

The ASN’s new guidance is designed to educate clinicians on these topics so they can arm patients and caregivers with the information they need to make wise food choices. 

The document provides easy to understand, practically applicable guidance from the ASN workgroup including adult nephrologists, pediatric nephrologists, practicing renal dietitians, nutrition scientists, a food scientist, and patients. It provides a clinical pathway to assess and reduce risk of harm from these additives. It also provides clear strategies to limit these additives.

What exactly are potassium and phosphorus additives?

Food additives refer to chemical compounds incorporated into food products to improve their shelf life, texture, taste, or appearance. Potassium, phosphorus, and other additives are used as food preservatives, stabilizers, flavoring agents, sweeteners, emulsifying salts, leavening agents, or acidity regulators. They can also be found in dietary supplements and medications.

The current food label lists a total amount of potassium from natural and artificial sources; in most cases, it is only an estimate. However, the total amount of phosphorus is not listed on the food label. The additives are simply noted in the ingredient section or left out.

The top 4 potassium additives in foods are potassium chloride, potassium phosphate, potassium citrate, and potassium lactate, but there are as many as 40 different potassium additives. 

There are over 240 phosphorus additives. You may find “phos” in the ingredient list (eg, di-, tri-, or polyphosphates), but not always (eg, lecithin and modified cornstarch). 

What are some common, surprising, and “hidden” food sources of these additives?

Additives can be found in many, many food items, whether canned, jarred, bottled, boxed, bagged, packaged, frozen, or cured. They’re found in sauces, dressings, and spice blends too. Salt substitutes commonly contain potassium chloride, and these products can contain a whopping 440 mg to 2800 mg potassium per teaspoon. 

Dark carbonated sodas (colas) and beverages all contain phosphorus additives. Deli meats are frequently infused with various additives. 

Enhanced or plumped meat cuts, including seemingly fresh chicken or seafood, may contain potassium phosphates. These products often contain statements, such as “brined,” “cured,” “contains solution,” or “natural flavorings.”

With the holiday season upon us, why is this topic more important than ever?

Holidays are known for food indulgences and eating more and different foods than we normally would. Family, friends, and neighbors are hosting get-togethers with full buffets, and food gifts abound. It’s all too easy to overload on calories – but also on food additives – during these times. That’s why many us make healthier eating one of our New Year’s resolutions.

It’s important for health care providers to arm patients with knowledge to prevent a health crisis and long-term health problems. Portion control and sticking to whole foods, such as fresh fruits, vegetables, whole grains, and fresh fish, poultry, and meat, can help. Watch out for those condiments!

How can potassium additives affect the health of patients with kidney diseases — positively or negatively? 

For patients with stage 1 through 3A CKD, added potassium may be beneficial. Mounting evidence from various clinical trials suggests increasing potassium towards the higher end of normal is beneficial for preventing malignant arrhythmias. 

On the other hand, patients with more advanced stages 4-5 CKD are at greater risk for hyperkalemia, especially if they’re taking potassium-sparing medications or have diabetes mellitus, metabolic acidosis, or constipation. 

How harmful are phosphorus additives to patients’ health?

There is no benefit from consuming phosphorus additives. Most individuals — with or without CKD — are consuming more dietary phosphorus than the recommended dietary allowance (RDA). 

Hyperphosphatemia, or excess blood phosphate levels, can lead to bone problems and calcification of soft tissue and blood vessels. These pathologic changes can result in CKD mineral and bone disorder. 

Some patients need to limit phosphorus additives. Others, such as those with overt cardiovascular disease or calcification, require intensive individualized strategies to directly reduce these additives in their daily diets. Renal dietitians are indispensable for achieving these goals. 

How can health providers apply ASN’s guidance to better care for their patients? 

We tried to make this guidance helpful for clinicians and patients alike. The strategies are presented by their level of complexity, healthcare team involvement, and patient burden – from easy, straightforward steps to stricter regimens. 

The guidance matches dietary interventions with patients’ disease severity, health literacy, and physical abilities. So, for example, if there is a patient with CKD that does not have a high risk of hyperkalemia or CKD-mineral and bone disorder, clinicians could provide basic guidance to help the patient eat healthier, including through balanced meals and portion control, incorporating more fresh fruits, vegetables, whole grains, legumes, nuts, and seeds. 

Another patient, however, may be at high risk for hyperkalemia due to a combination of advanced CKD, diabetes, constipation, and use of an ACE inhibitor. The renal dietitian can do a comprehensive diet history and work with that patient to limit certain foods that contain potassium additives. 

How can a renal dietitian help patients navigate the complex food choices?

Renal dietitians can help patients with food literacy, gauge motivation for change, assess food diaries or recalls, and develop individualized strategies, including demineralizing cooking techniques. They may also be able to help patients access healthy foods, if patients are food insecure or reside in neighborhoods with few grocery stores.

What special populations particularly need a renal dietitian?

All individuals with CKD would benefit from seeing a trained renal dietitian, including those on maintenance dialysis. Additionally, children and kidney transplant recipients have unique nutrition and dietary needs that are best served by a renal dietitian. Excess additives can be harmful to children due to their smaller body size. Kidney transplant recipients taking immunosuppressive drugs may experience adverse consequences when they consume too much of these additives.