To reduce the potassium content in vegetables, the National Kidney Foundation recommends leaching them prior to cooking or eating. To leach vegetables such as potatoes and squash, peel, thinly slice and soak the vegetables for two hours in warm water. Use ten times the amount of water as vegetables.
Another way to leach vegetables is to boil the vegetables twice and discard the cooking water afterward. Also discard any liquid from canned vegetables. Even with leaching, the vegetables still retain some potassium. Thus, individuals with kidney problems may need to limit the number of servings and strictly follow portion recommendations for particular potassium-rich vegetables.