Kidney Coach

Potassium Leaching – Study Shows Not All Leaching Methods Work

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Just thought I would tell you about this really cool study I saw today. Some of you may already know that one of the key nutrients to avoid in kidney disease is potassium (from food). Now potassium is an essential nutrient, and in particular a VERY good nutrient for the heart – in fact, one of the best remedies for high blood pressure is taking a potassium supplement. However in kidney disease it is very easy for the levels of this nutrient to sky-rocket in the blood – due to the fact that the body (kidneys) can no longer maintain the ideal levels necessary for optimal health. This is not the case for everybody with kidney disease, so it is a good thing to have your levels checked at your next blood test.

One of the best ways to manage your potassium levels is to limit the amount of foods that contain high amounts of potassium. As you will see this is easier said than done! This is because most of the ‘healthy’ foods contain high amounts of potassium: fruit, vegetables, and nuts. So what to do? Well you may have heard that there is a technique called potassium leaching; potassium leaching is a simple method used to ‘leach’ out some, or the majority, of potassium.

Here is a typical method for leaching potassium from vegetables:

  • Peel the vegetable, cut into small pieces.
  • Rinse the vegetables thoroughly.
  • Fill a pot of water and place the vegetables within to soak for a minimum of four hours at room temperature (or you can let them soak overnight in the refrigerator).
  • After soaking, rinse the vegetables with fresh water.
  • Cook vegetables as desired.

Ordinarily this method works a treat, but what some of you may not know is that this method will not work for all vegetables. Damn! … But don’t worry I have come across a solution 🙂

Jerrilynn D. Burrowes, PhD, RD & Nicholas J. Ramer, PhD conducted a study to measure the amount of potassium loss in tuberous root vegetables using different methods. The tuberous root vegetables used in the study were: fresh and sweet batata, cocomalanga, dasheen, eddo, black yam, white yam, yellow yam, yampi, malanga, red yautia, white yautia, and yuca. These are not the most common vegetables in the world, but they chose these because of their high fibrous density. Why? Well if you can reduce the potassium in these vegetables, then the same techniques will apply to the softer more porous vegetables.

Five experiential environments were created using varying soak times and cooking methods, and they analysed the potassium levels of each vegetable using atomic absorption spectrophotometry (= fancy technical term), and the residue of dried vegetables.


The results were very interesting – what Burrowes & Ramer discovered was that the traditional and most common method of leaching potassium from vegetables wasn’t worth your time at all! There was virtually no difference between soaking these vegetables and not soaking them. What they did find out which is of interest, is that double cooking (double boiling) is the only sure way to reduce potassium levels significantly in most vegetables. One round of boiling helps, but the clear winner was the double cooking method.

So what does this mean for you? Start double cooking!

Here is the NEW method for leaching vegetables:

  • Peel the vegetable, slice into small pieces (roughly 3mm width).
  • Wash the vegetables thoroughly, and rinse.
  • Fill a pot of water and place the vegetables within to boil (2:1 ratio / water:vegetables).
  • Bring to the boil, and then drain water off.
  • Fill pot again with water (2:1 ratio), and boil until soft, but integrity is retained.
  • And you’re done!

So to summarise:

  • You can’t beat the double cooking method; it is simply the most effective potassium leaching method to date.
  • Not all kidney disease patients need to watch their potassium levels, so check with your doctor.

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