When living with CKD, you may have been told to monitor your potassium, phosphorus, and sodium intake. In this post we will be focusing on potassium and potassium bioavailability. Let’s dive in!
What is potassium?
Potassium is an element on the periodic table, a soft, silver metal, but is also an essential micronutrient in our diet. Potassium helps maintain the fluid levels in our cells as well as playing a critical role in muscle contraction. Potassium has an inverse relationship with sodium in our bodies making them both important to monitor when one has CKD.
How much potassium do I need?
Potassium is a mineral with an adequate intake (AI) value in Canada. This AI value is an estimate based on scientific evidence and approximates what the mean daily intake of potassium should be for the average person. For adult men, 3400 mg/day is recommended and for adult women, 2600 mg/day is recommended. For CKD patients this value could be too high if your blood potassium is high and should be modified to follow a low potassium diet.
Potassium and CKD
With potassium and CKD you may be asked to follow a low potassium diet. A low potassium diet with CKD is 2000 mg/day. You should try to choose food with less than 200 mg of potassium per ½ cup serving. All nutrition labels list the amount of potassium per serving, allowing for easier tracking of this mineral. CKD patients need to track potassium consumption because the kidneys cannot excrete any excess potassium, and excess potassium can lead to hyperkalemia, which can lead to irregular muscle contractions which is particularly dangerous in the heart muscle. Something important to consider when tracking potassium is not only the amount of potassium in a serving, but also the potassium bioavailability.
Similar to phosphorus, bioavailability, in the context of potassium consumption, means how much of the potassium in a food will we actually digest and subsequently absorb in our bodies. The concept of potassium bioavailability is a relatively new area of research and has subsequently not been accounted for in the current guidelines. Newer research has suggested that although fresh fruits and vegetables are often high in potassium, their bioavailability is likely to be around 50-60%. The proposed explanation for this is that plant cell walls are difficult for us to digest, meaning the potassium attached to the cell walls are not being released when we are eating the fruits and vegetables. Potassium that is not bound to cell walls, so any potassium source that is not from plant sources (i.e. animal or additive sources), will have a much higher bioavailability. Research has found that potassium additives like potassium chloride and potassium gluconate have very high bioavailability of over 90%, so we want to always avoid these if we have high potassium.
What does this mean for potassium and CKD?
So if you are limiting potassium and CKD here are a few thing to consider.
Reading food labels is important not only for the potassium content on nutritional labels but also for potassium additives in the ingredient list. Common potassium additives to look out for are potassium chloride, potassium phosphate, potassium lactate, and potassium citrate. Foods that commonly contain potassium additives are processed meats, low sodium foods or foods containing sodium substitutes, drink powders, and electrolyte drinks. This is a helpful resource provided by BC Renal Services is a great starting point for label reading.
Although fruits and vegetables are sometimes high in potassium, it should be considered that only around 50-60% of it will likely be absorbed. Ultimately, when trying to monitor potassium levels, the new concept of potassium bioavailability points toward patients focusing on avoiding potassium additives, rather than fruits and vegetables and speaking with a renal dietitian can help you personalize your diet.
This article was written by Rachel Rosenberg, Nutrition Student Volunteer.
This article was reviewed by Emily Campbell, RD CDE MScFN.