One of the critical functions of the kidneys is maintaining homeostasis. Homeostasis refers to the body's ability to adjust its internal environment in order to sustain life. The kidneys help maintain homeostasis by keeping blood pressure, hemoglobin and blood levels of various minerals within healthy ranges. As kidney disease progresses, kidneys are less able to perform these important functions. With respect to potassium, severely scarred kidneys can no longer filter excess potassium in the blood. This means that potassium levels can get dangerously high unless proper precautions are taken.
Functions
As explained in the text "Clinical Methods" by H. Kenneth Walker et al., the difference between the levels of potassium inside the cell and outside the cell creates nerve impulses, helping the heart beat regularly. MedlinePlus notes that too much potassium in the extracellular fluid can cause missed heartbeats or heart attacks.
Monitoring
Since excess potassium has such severe consequences, nephrologists regularly monitor their patients' serum potassium levels by performing regular blood tests. The frequency of monitoring depends on the type of kidney disease and how advanced the disease is. Generally, patients with advanced disease are monitored more frequently than patients in the early stages of disease.
Guidelines
The National Kidney Foundation has established healthy levels of potassium for kidney patients. Levels between 3.5 and 5.0 milliequivalents per liter are considered safe. Levels between 5.2 and 6.0 are marginally safe. Levels higher than 6.0 are dangerous. Patients who have safe levels of potassium will not benefit by limiting the amount of potassium in their diets. Potassium restriction is advised only for patients whose potassium levels are higher than 5.2.
High-Potassium Foods
Patients often struggle with low-potassium diets, because potassium is in most food. Portion control is important, because even a low-potassium food can create high levels of potassium in the body if the patient eats too much of it.
Many foods considered healthy for the general population are high in potassium, making them risky for many kidney patients. The National Kidney Foundation points out that apricots, avocados, cantaloupe, grapefruit juice, mangoes and oranges are all high-potassium foods. Likewise, milk, cheese and yogurt should be consumed in small quantities, because they also contain a significant amount of potassium.
Alternatives
Patients on a low-potassium diet can eat a wider variety of foods if they leach potassium out of high-potassium vegetables. The National Kidney Foundation advises cutting potatoes, sweet potatoes, carrots and beets into small pieces and soaking them in 10 times their volume of warm water for at least two hours. Rinse the vegetables, then cook them in five times more water than vegetable. For instance, two cups of vegetables should be cooked in at least 10 cups of water.
