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I have kidney disease... should I avoid potassium?!


Before we answer that question, let’s talk about why potassium is important for us in general.


Potassium plays many vital roles in the body. It is both a mineral and an electrolyte. It helps regulate the amount of fluid in all cells of the body, keeps your heartbeat regular, helps nerves function and muscles contract. It can help to off-set the blood pressure raising effects of sodium. The kidneys keep blood potassium in the normal range by excreting excess potassium in the urine.


Dietary surveys have shown that Americans consume too much sodium and not enough potassium. Low potassium intake is associated with high blood pressure, stroke, poor bone health, increase risk of kidney stones and type 2 diabetes. Suboptimal potassium intake of the population prompted the Dietary Guidelines for Americans to list potassium as a “nutrient of concern” and add it to the food label. Recommended daily intake of potassium is 4,700 mg or more.


But I was told to limit potassium because I have kidney disease…


A low potassium diet (less than 2,000 mg) is a standard recommendation for those with late to end stage kidney disease. This is because, when kidney function declines, the kidneys are unable to get rid of the excess potassium in the blood. High blood potassium can lead to abnormal heart rhythms which can cause heart attack. The idea that high potassium foods lead to high blood potassium was actually based on theory, not vigorous studies. Newer research is showing a low potassium diet is actually associated with higher risk of death in those with end stage renal disease.


So I’m damned if I do, damned if I don’t?!


Here is so good news. Just because you have kidney disease it doesn’t mean you need a low potassium diet! If someone is first diagnosed with kidney disease, they may search the internet for what diet to follow. The articles that pop up will likely recommend a low potassium diet. However, high blood potassium typically does not manifest early in kidney disease. Even in the later stages, potassium may remain at normal levels. Limiting potassium too early can lead to more decline in kidney function.


There are several non-dietary factors that can impact potassium levels in the blood including medications, gastrointestinal issues (constipation, diarrhea, vomiting), bleeding, metabolic acidosis and hydration status. If you are dealing with high potassium, it’s important to address these issues with a healthcare professional. Ask if any of your medications can cause high potassium, how to manage constipation, if your body’s acid/base balance is off.


What foods contain potassium?


Many fruits, vegetables, nuts, seeds, beans, legumes and meats are good sources of potassium. Bananas, oranges, cooked spinach, butternut squash, avocado, black beans are some common high potassium foods you may be familiar with. Obviously, these are all very healthy foods! But there is another source of dietary potassium that doesn’t get much talk. Much like phosphorus, potassium can be added to food.


Due to concerns of American's high sodium intake, many food companies have switched from using sodium to potassium in processing. A recent investigation showed that foods with potassium additives can contain up to 900 mg potassium/100 g compared to 325 mg/100 g for a non-potassium additive product. Potassium additives are commonly found in “reduced sodium” products such as soups, as well as dairy products and meats. However, this added potassium isn't where we want to be getting the majority of our potassium from.


My previous blog post reviewed the bioavailability of phosphorus. Potassium found naturally in foods and potassium additives also have different bioavailability's…


I did mention above that meats contain potassium. Meats are thought to have a higher bioavailability of potassium compared to whole fruits and vegetables due to differences in cell structures. Plant cells are bound by cell walls and animal cells are not. Potassium is mostly inside the plant cells and since the cell walls are more difficult to digest, the potassium is not as readily absorbed. Since potassium in animal cells are not bound by cell walls it is more easily absorbed. And similar to phosphorus, potassium bioavailability from food additives can be up to 100% compared to only 50-60% in whole fruits and vegetables. Thus someone with late/end stage kidney disease consuming lots of processed foods is more at risk for high potassium levels.


In summary…


Lack of dietary potassium is a public health concern and it is attributed to inadequate intake of whole plant foods. A blanket potassium restriction is not warranted for every person who has kidney disease and can lead to worse health outcomes. Make sure you rule out other causes of high potassium with your medical team. Be aware of potassium in processed foods as this can increase the potassium content up to three times.


There are definitely times where a low potassium diet is warranted and it’s important to work with a registered dietitian to ensure you are still getting in quality nutrition. There are many benefits of eating plant-foods and concern over potassium should not be a reason to choose a low quality diet full of processed foods. Kidney nutrition is always evolving and I hope I was able to shed some new light on potassium for you!




References:

Picard K, 2018 ‘Potassium Additives and Bioavailability: Are We Missing Something in Hyperkalemia Management?’ Journal of Renal Nutrition, vol 29, no 4, pp 350-353


KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update


St-Jules D, Goldfarb D, Sevick M, 2016 ‘Nutrition Non-equivalence: Does Restriction High-Potassium Plant Foods Help to Prevent Hyperkalemia in Hemodialysis Patients’ Journal of Renal Nutrition, vol 26, no 5, pp 282-287


Sussman E, Singh B, Clegg D, Palmer B, Kalantar-Zadeh K, 2020 ‘Let Them Eat Healthy: Can Emerging Potassium Binders Help Overcome Dietary Potassium Restrictions in Chronic Kidney Disease?’ Journal of Renal Nutrition, vol 30, no 6, pp 475-483

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