The RenalTracker Team
September 16, 2019

Potatoes are a versatile root crop that can be enjoyed in many ways such as crispy French Fries, delectable mashed potatoes, and potato salad.

Whatever the occasion and however it may be prepared, potatoes have long since become a staple ingredient in household dishes. It has, in a way, earned its place in our homes.

But do potatoes still have a place for someone on a renal diet?

Spud 101

Potatoes, scientifically known as Solanum tuberosum, are grown for their starchy edible tubers and are considered one of the main food crops worldwide. These underground-growing crops are also rich in essential vitamins and minerals -- vitamin C, thiamine, and niacin, to name a few. Potatoes are, however, also rich in potassium. A medium-sized baked potato has 610 mg.

How much potassium is in potatoes?

According to the USDA Database, a medium-sized potato (roughly 213 grams & about 2¼-3 ¼ inches in diameter) contains the following nutrients: 

Potatoes (medium-sized)

Sodium

13 mg

Protein

4.37 g

Potassium

905 mg

Phosphorus

121 mg

Calcium

26 mg

Calories

164 kcal

Fat

0.19 g

Water

168.80 g

Carbohydrates

37.25 g

The suggested potassium intake limit for people with kidney disease, per the National Kidney Foundation (NKF), is 2000 mg (or less) daily.

Considering that, it would mean that a single potato can give you almost half of your daily potassium intake in one sitting! That's not accounting for the amount of potassium you get from the other food items you eat during the day.

The safe amount of potassium in the blood

Your monthly level of potassium is measured in millimoles per liter of blood (mmol/L), which can be categorized into 3 levels:

  • 3.5 to 5.0 mmol/L is a SAFE Zone.
  • 5.1 To 6.0 Mmol/L is a Caution Zone. 
  • 6.0 Mmol/L Or Higher is a Danger Zone.

The Effects of High Potassium Content on CKD Patients

Potassium functions as a regulator of fluids in the body, helps in the proper function of muscles and sends nerve signals throughout the body. It, therefore, plays a major role in regulating muscle and heart contractions, reducing HBP as well as water retention, preventing the formation of kidney stones and even preventing Osteoporosis. The body uses the potassium it needs and removes the excess nutrient through the kidney. Efficient functioning kidneys can clean up to159 quarts of blood per day, removing excess waste materials into 1 to 2 quarts of urine. The kidneys also balance the amounts of sodium, potassium, and phosphate in the blood.

If you have Chronic Kidney Disease, your kidneys may have difficulty removing the extra potassium in your blood. This, in effect, could increase the potassium level in your blood.
Unfortunately, many people don't feel the symptoms of high potassium until they worsen.

 Too much potassium in the body is called hyperkalemia, which symptoms include:

  • Diarrhea
  • Abdominal pain
  • Nausea
  • Chest pain
  • Irregular heartbeat or heart palpitations. 
  • Muscle weakness 

Other than consuming high-potassium food, certain CKD medications such as ACE inhibitors and diuretics can also spike potassium level in the blood. CKD patients with diabetes may struggle to remove potassium from the blood. Call your doctor if you are experiencing hyperkalemia symptoms.

Can potatoes be included in a CKD diet?

Despite the health benefits of potatoes, CKD patients are encouraged to lay low on potatoes as they are high in potassium. However, some cooking methods can reduce the total potassium content in the potato. You can still enjoy potatoes, albeit in small, dietitian-approved portions, and through a preparation method called... leaching.

Leaching

Leaching is a process of removing potassium from food by extracting and dissolving it in a liquid. You don't have to completely give up high-potassium vegetables; however, you would simply need more time to prepare them.

 Here's how you can do it:


  1. Peel and place potatoes in cold water (to avoid darkening).
  2. Slice into 1/8 inch thick pieces and briefly rinse in warm water.
  3. Soak in warm water for a minimum of 2 hours. Use ten times the amount of water to the amount of vegetables (e.g., 10 cups of water for 1 cup of vegetables).
  4. Rinse in warm water again for a few seconds
  5. Cook vegetables. Use five times the amount of water to the amount of vegetables (e.g., 5 cups of water for 1 cup of vegetables).

Cutting, slicing thinly, or grating the potatoes is an effective way to minimize potassium content. You can reduce half the original amount of potassium when you boil the potatoes for at least 10 minutes in a large pot of water. The amount of potassium, after leaching, ranges from  100 to 200 milligrams in half a cup serving.

A study conducted by the National Library of Medicine (https://pubmed.ncbi.nlm.nih.gov/31444038/) among fresh potatoes, canned potatoes, frozen French fried potatoes, soaking potatoes after normal cooking is found to leach up to 70% of the potassium. This process leaches the potato up to 130 mg/100g edible portion. 

Frying the potatoes didn't leach the potassium but increased it instead. A 100 gram of French Fries in food chains has 579 milligrams of potassium. In contrast, the large serving can have 890 mg potassium, almost half of the recommended daily intake. On the other hand, canned potatoes go through natural leaching as these potatoes are soaked in water.

The least effective potassium reduction method is soaking the potatoes in the fridge and cooking them without boiling.


The Bottom line

Potatoes are rich in vitamins, minerals, and antioxidants that can be beneficial to the body. They are also filling which can be beneficial for those who want to curb hunger pains and cravings. However, if you have kidney disease, you may want to reconsider eating this vegetable as it can affect your potassium level. Too much potassium level in the body (called Hyperkalemia) can be hard on your kidneys. Kidneys will have a hard time removing excess potassium from your blood that could result in vomiting, diarrhea, nausea chest pain, and heart palpitations. 

If you wish to include potatoes in your renal diet, you can leach or double boil to reduce potassium content in the potatoes. Bear in mind to watch your portion size though since these cooking methods still have great potassium content. It is still important to talk to your doctor or dietitian to know your recommended daily potassium intake.

Sources:

Is It Possible to Include Potato in the Diet of Chronic Kidney Disease Patients? New Culinary Alternatives for Limiting Potassium Content - https://pubmed.ncbi.nlm.nih.gov/31444038/

Potassium. - https://medlineplus.gov/potassium.html#:~:text=It%20helps%20your%20nerves%20to,harmful%20effects%20on%20blood%20pressure.

High potassium (hyperkalemia) - Causes, Prevention & Treatment.
https://www.kidneyfund.org/kidney-disease/chronic-kidney-disease-ckd/complications/high-potassium-hyperkalemia.html

Is It Possible to Include Potato in the Diet of Chronic Kidney Disease Patients? New Culinary Alternatives for Limiting Potassium Content - https://pubmed.ncbi.nlm.nih.gov/31444038/

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