By Sharon Turban, MD, MHS
Potassium is a very important mineral needed by the body to maintain proper health. However, most individuals with kidney disease must closely monitor their potassium intake. As Dr. Sharon Turban shows us, we can have too much of a good thing.
What is potassium and what does it do?
Potassium is a very important mineral. It plays a key role in controlling the function of nerves and muscles, particularly the heart. Potassium is found in many foods, especially many fruits and vegetables. It has been shown to lower blood pressure and may also have benefits such as reducing the risk of strokes. Most of the extra potassium eaten in the diet is removed by the kidneys. When kidney function decreases to a certain level, the body cannot get rid of the extra potassium and potassium levels may rise. Therefore, it is important for people with kidneys that are not healthy to learn more about potassium and to be aware of how much potassium they consume.
What can happen if potassium levels are too high or too low?
If potassium levels become too high (for example, if too much potassium is taken in and kidney function is not good enough to remove the extra potassium, or if potassium levels rise due to certain medications), then serious and potentially life-threatening side effects can occur. These effects may include weakness, irregular heartbeat/palpitations, numbness, tingling or even death. Similar side effects can also occur if potassium levels are too low. Other effects of very low potassium include muscle cramping, nausea, vomiting and confusion. Potassium levels could become too low if intake is very low, if diarrhea is present (some potassium is lost through the stool), or from certain medications such as some fluid pills. In kidney disease patients, severely low potassium levels, particularly low enough to cause problems are not as common as high potassium levels. It is also important to know that people with low or high potassium levels may NOT have any symptoms or may have vague symptoms. This is why it is very important to make sure that your blood work is monitored regularly and that you follow the recommendations of your health care providers. And if you do notice any of the previously stated symptoms, make sure to seek medical care immediately!
How much potassium is safe for you?
For people without kidney problems, the kidney is very good about controlling the right amount of potassium in the body. It is recommended that people with healthy kidneys take in at least 4.7 grams of potassium each day. In early stages of kidney disease, problems with high potassium typically do not occur because the kidneys are still able to get rid of extra potassium. However, for people whose kidneys are not functioning normally, there comes a point when the kidneys can no longer remove extra potassium. A buildup of potassium can be very dangerous. More research still needs to be done so that we understand how much potassium people with kidney problems should take in. The current recommendations by the National Kidney Foundation are that people with mild to moderate kidney disease (not on dialysis) take in 2 to 4 grams of potassium per day. However, this has not been well-studied yet and also in part depends on how severe your kidney function is or if you are on medications (such as angiotensin converting enzyme inhibitors, angiotensin receptor blockers, or fluid pills) which may raise or lower your potassium levels, and other factors.
What should you do?
If you have kidney disease, you should follow up with your doctor(s) and have your kidney labs checked regularly (this includes your potassium level). The SAFE range of blood potassium levels is 3.5-5.0 mEq/L. If your level is lower or higher than this, you should talk to your doctor and to a kidney dietitian to find ways to get your potassium level into the safe range. You should also make sure that all of your doctors are aware of your kidney problem, because there are certain medications that you should avoid when you have kidney disease which can raise your potassium to high levels.
What if you have been told that your potassium level is on the high side and that you should limit your potassium intake?
It is very important to speak with a kidney dietitian and with your doctor to discuss ways to limit your potassium intake if your potassium level is high or your kidney function is becoming severely impaired. Many fruits and vegetables, although otherwise healthy, are often high in potassium, and may need to be limited. Most people know that bananas and oranges are high in potassium, but other fruits that are high in potassium include: avocados, cantaloupe, papayas, honeydew melons and mangoes. High-potassium vegetables include: potatoes, beans (except green beans), spinach, tomatoes and winter squash. Milk products and chocolate are also high in potassium.
One problem with a low potassium diet is that many otherwise healthy foods such as fruits and vegetables are high in potassium. However, there are several fruit options that you can choose which are lower in potassium. If you are advised to lower your potassium intake, you can choose lower potassium fruit options such as: apples, berries, grapes, watermelons, peaches, plums or pineapples. Fruit drinks like apple, cranberry or grape juice are lower in potassium than orange juice. Vegetable options that are lower in potassium include green beans, summer squash, onions and bell peppers.
Vegetables, including potatoes, can be leached (peeled, cut into small pieces, rinsed and soaked for at least four hours, then rinsed again) to lower the potassium content.
Other tips for keeping potassium at safe levels:
- Remember to watch your portion size, • because even if you eat low potassium foods, the potassium can build up if you eat large portions.
- Throw away the liquids found in canned fruits • and vegetables.
- Use caution with salt substitutes. Although lowering sodium intake is extremely important, you should be extremely careful with salt substitutes (including low-sodium packaged foods) because many of them contain potassium!
- It is important to read food labels carefully, but please note that food companies are NOT required to list the potassium content on food labels. So, foods can be high in potassium, but the label will not tell you how much potassium is in the food. If you are unsure of certain foods, talk to your doctor or a renal dietitian.
Hopefully, with additional research, we will have more answers to guide you! You can also go to http://www.kidney.org/atoz/content/potassium.cfm to find out more information about potassium in foods or visit https://aakp.org/center-for-patient-research-and-education/educational-brochures-and-resources/ to download a free copy of the American Association of Kidney Patients’ Nutrition Counter. This educational piece lists the potassium, phosphorus, sodium, protein and calories in more than 300 commonly eaten foods.
Again, be sure to see your kidney doctor and kidney dietitian regularly! Keeping potassium levels healthy and following a low-sodium diet and other recommendations by your health care team are important ways to keep your body healthy!
Dr. Sharon Turban, MD, MHS, Assistant Professor of Medicine at Johns Hopkins University, is a kidney doctor whose research interests include investigating the effects of diet on blood pressure and kidney function. She is the author of several papers and book chapters, including those related to sodium and potassium and the kidney. Dr. Turban is the principal investigator of the Chronic Kidney Disease-Potassium (CKD-K) trial, which is looking at the effects of different levels of potassium intake on patients with chronic kidney disease.
This article was originally published in aakpRENALIFE, January 2011