Moving to a Plant-Based CKD Diet (Part 1): Can Foods High in Potassium and Phosphorus Be Included in Your Diet?
By Stephanie Legin RD, LDN
WHY SHOULD YOU STRIVE FOR A MORE PLANT-BASED DIET?
Moving to a plant-based diet has many health benefits. Research has shown that diets that include more plant-based foods can help reduce your risk for cardiovascular disease, manage diabetes, supply a wide variety of immune boosting and anti-inflammatory phytochemicals and antioxidants, and provide adequate dietary fiber to help reduce cholesterol and maintain a healthy digestive tract.
Unfortunately, many plant-based foods are high in potassium and phosphorus. If you have CKD, you may have to limit or avoid consuming these foods. How much you can consume depends on your level of kidney function. Your nephrologist and your renal dietitian monitor your kidney function and advise you on your dietary restrictions.
WHERE DO YOU FIND POTASSIUM AND PHOSPHORUS IN PLANT-BASED FOODS?
Potassium is found in:
- Beans, nuts, nut butters and seeds
- Soy and soy based foods
Phosphorus is found in:
- Beans, nuts, nut butters and seeds
- Soy and soy based foods
- Whole wheat/bran based foods, brown rice, whole grain breads and cereals
- Any plant-based processed food that has had inorganic phosphorus added to it
Phosphorus consumed from unprocessed, natural plant-based sources is absorbed at 40-50% by your body. Phosphorus consumed from inorganic sources is absorbed at 100%.
WHAT CAN YOU DO IF YOU HAVE CKD AND WANT TO EAT A MORE PLANT-BASED DIET?
Fortunately, there are few ways to help reduce the amount of potassium and phosphorus in some of these plant-based foods and help you fit them into your CKD diet.
- Reduce your portion sizes of high potassium or phosphorus foods. Typically, portion sizes are ½ cup or one medium piece. Cut portions in half and only eat ¼ cup or half of a medium piece. Half the amount eaten=half the amount of potassium and phosphorus.
- Limit servings of high potassium foods to one per day and servings of medium potassium foods to two per day. Refer to the article, “Chronic Kidney Disease and Potassium: A Guide for the CKD Patient” for lists of low, medium and high potassium content foods. https://kidneychef.com/chronic-kidney-disease-and-potassium-a-guide-for-the-ckd-patient/
- Swap canned fruits and vegetables for their fresh or frozen counterparts. The potassium in canned goods leaches into the water or juice in the can.
- Discard the fluid from canned fruits and vegetables as they will contain the potassium that leached from the food.
- Rinse canned goods for more potassium removal before cooking or eating.
- Always choose unprocessed or minimally processed plant-based foods to include in your diet.
- Avoid processed plant-based foods that may have potassium and phosphorus additives.
- You can identify if a food has potassium and/or phosphorus additives by reading the ingredient list. Refer to the articles, “Chronic Kidney Disease and Potassium—Beyond the Basics” and “Get the Facts on Phosphorus Additives” for information on how to identify foods with added potassium and/or phosphorus. https://kidneychef.com/chronic-kidney-disease-and-potassium/, https://kidneychef.com/the-facts-on-phosphorus-additives/
- Unfortunately, it is very difficult to identify if and how much phosphorus is in a food. Nutrition Facts Labels are not required to list the amount of phosphorus in a food. You can only identify if a food has added phosphorus by reading the ingredient label.
- Your level of kidney function will dictate your phosphorus limitations. Typically, limiting phosphorus intake to 800-1000mg/day is recommended.
- Practice cooking techniques that lower the potassium and phosphorus content of foods (see below).
- If you use the soak and boil method of cooking, limit your servings of plant-based foods that used to be high in potassium and phosphorus before cooking, to a maximum of three per day.
HOW SHOULD YOU COOK PLANT-BASED FOODS TO REDUCE POTASSIUM AND PHOSPHORUS?
Potassium and phosphorus are both minerals that can be reduced in foods if they are prepared a certain way. Unfortunately, not all cooking methods will reduce the amount of potassium and phosphorus. In fact, some methods can actually increase the amount. For instance, drying one cup of grapes to make one cup of raisins, increases the amount of potassium in them by 4 times.
Soaking (aka “leaching”) and boiling high potassium and phosphorus foods in water seems to be the most effective method of reducing the amount of these minerals in food. Research has shown that soaking and then cooking raw, fresh produce in boiling water can decrease the amount of potassium in foods by 50-80%. Soaking and boiling canned foods, particularly legumes, has been shown to reduce the amount of potassium further to almost 95%. Studies show a reduction in phosphorus content as well; however, not as significant as potassium.
Unfortunately, not all plant-based foods can be soaked and boiled to reduce potassium and phosphorus content such as bananas and oranges. For that reason, these foods would have to be avoided or eaten in smaller portions and less frequently than other plant-based foods.
Prior to soaking and cooking your food, peeling and the size of the pieces will affect how much potassium and phosphorus is leached out. Removal of peels and cutting into smaller pieces, the more minerals will be leached out due to greater surface area being exposed.
For example, soaking and boiling 1” peeled, cubed potatoes will reduce potassium content by 50 percent. Soaking and boiling peeled, shredded potatoes will reduce potassium by 75 percent.
It is important to remember that soaking and boiling will not pull all of the potassium and phosphorus out of the food.
- Peel and dice your food into at least 1 inch pieces.
- Place the food in a pot and fill with water until completely covered.
- Soak for a minimum of two hours (the longer the soak, the more mineral is leached out).
- If soaking longer, change the water every four hours.
- Discard the soaking water.
- Fill the pot up with fresh water before cooking.
Evolving your diet to a more CKD plant-based diet is possible but requires a lot of planning, preparation, diligence and dedication to achieve. Work closely with your renal dietitian and MD to monitor your bloodwork and discuss your dietary limits to ensure you are eating the right foods for you.
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