Potassium Restriction for kidney patients and renal disease. Potassium is restricted for a kidney patient only when the urine begins decreasing and kidney function is reduced to 20% to 30%. So in this case the kidney problem diet and foods to avoid for this type of kidney diseases are those with high Potassium foods. Foods having high value of potassium content include Bananas, Prune Juice Oranges, Orange Juice, Milk, Prunes, Tomato Juice, Tomato Sauce, Nuts, Chocolate, Dried peas and Beans.