Understanding Nutrition: How Much Potassium Do Boiling Potatoes Remove?

October 10, 2025 •

4 min read

According to the Dietary Guidelines for Americans, a medium baked potato with skin contains over 900 mg of potassium, making it a high-potassium food. For many people, this is a nutritional benefit, but for those with kidney disease, it can be a health concern that raises the question: how much potassium do boiling potatoes remove? The answer depends on your preparation methods, as boiling can significantly reduce this mineral.

Quick Summary

Boiling potatoes reduces their potassium content by leaching the mineral into the cooking water. The amount removed is influenced by peeling, cutting size, and boiling method. This is a vital technique for managing dietary mineral intake, particularly for those on low-potassium diets for kidney health.

Key Points

Boiling reduces potassium: Potassium is a water-soluble mineral, and boiling potatoes leaches it into the cooking water, effectively reducing the mineral content of the food.
Simple boiling removes 22-30%: A single boil of peeled, diced potatoes can remove about 22% to 30% of the potassium.
Double-boiling removes around 50%: For a more significant reduction, the double-boiling method (boiling, draining, and re-boiling) is recommended, which can remove up to half of the potassium.
Boil and soak is most effective: The most potent technique involves an initial boil followed by soaking for several hours, which can remove up to 70-85% of potassium.
Cutting smaller pieces is crucial: Peeling and cutting potatoes into smaller pieces, like strips or dice, increases the surface area and maximizes the amount of potassium that leaches out during cooking.
Baked potatoes retain potassium: Cooking methods that use little to no water, such as baking or microwaving, cause minimal potassium loss, and are not recommended for those on a low-potassium diet.
Discard the water: Always discard the cooking water after boiling, as it contains the potassium that has been leached from the potatoes.

Potatoes are a staple food for many around the world, known for their versatility and nutritional value. They are an excellent source of vitamin C, fiber, and important minerals, including a significant amount of potassium. While potassium is essential for proper nerve and muscle function, and for maintaining normal blood pressure, too much of it can be dangerous for individuals with chronic kidney disease (CKD) whose kidneys are less efficient at filtering it out. This has led many to seek effective ways to reduce the potassium content in their food, with boiling being one of the most common methods.

The Science of Leaching

Potassium is a water-soluble mineral, meaning it dissolves in water. The process of leaching involves removing a substance from a food by submerging it in water. When potatoes are boiled, the potassium naturally moves from the potato into the surrounding water. The amount of potassium that leaches out is directly affected by several factors related to the boiling process itself.

Factors Influencing Potassium Removal

Surface Area: The more surface area of the potato that is exposed to the water, the more potassium can be removed. This is why cutting potatoes into smaller pieces, such as strips or dice, is far more effective than boiling them whole. Research has shown that shredding potatoes can achieve even greater reductions.
Water Volume and Duration: Using a generous amount of water for boiling helps draw out more of the mineral. Boiling for a longer duration also increases the amount of potassium removed. It is crucial to discard the cooking water, as it is now concentrated with potassium.
Soaking Technique: While some traditional methods involved soaking raw potatoes overnight, studies show this is largely ineffective at removing potassium. The most effective method involves boiling the potatoes first, which alters the structure of the potato, making the potassium more accessible. Soaking the cooked potato in fresh, clean water for several hours after the initial boil dramatically increases leaching.

Quantifying Potassium Removal through Boiling

Simple boiling of peeled and cut potatoes can reduce potassium content by approximately 22% to 30%, depending on the cut and duration. However, more intensive techniques are necessary for individuals requiring very low potassium levels.

Double-Boiling: This involves boiling the peeled, chopped potatoes for a period, draining the water, and then boiling again in a fresh pot of water. This method can remove about 50% of the original potassium.
Boil and Soak Method: This is the most effective method, especially for those on a strict renal diet. It involves a two-step process: (1) boil the peeled, cut potatoes for about 8-10 minutes, (2) drain and discard the water, and (3) soak the boiled pieces in a large amount of clean, warm water for at least 12 hours. Studies show this can remove up to 70-85% of potassium.

Comparison of Cooking Methods

To illustrate the difference in potassium retention, the following table compares various cooking methods for 100g of potato. A raw potato contains approximately 454 mg of potassium per 100g.


Cooking Method	Preparation	Approx. Potassium (mg/100g)	Approx. Reduction (%)	Notes
Raw	Peeled	454	0%	Benchmark for comparison.
Boiled	Peeled, diced	287-295	30-37%	A significant reduction from standard boiling.
Double-Boiled	Peeled, diced	~245	~50%	Effective for a moderate reduction.
Boil + 12hr Soak	Peeled, strip-cut	41	~91%	Highly effective for strict low-potassium diets.
Boil + 12hr Soak	Peeled, diced	122	~73%	Effective, but less so than strips due to less surface area.
Baked/Microwaved	Whole, unpeeled	>454	<5%	No water leaching, can concentrate nutrients.
Canned (Drained)	Drained, rinsed	105-118	~75%	Potassium leached during commercial canning process.

Best Practices for Lowering Potassium in Potatoes

For those who need to minimize their potassium intake, mastering the preparation process is key. The boil-and-soak method, also known as "leaching," is the most effective technique for significantly reducing potassium levels. Here is a step-by-step guide:

Peel and Cut: Always peel the potatoes and cut them into smaller, thinner pieces (strips or thin slices are best) to maximize the surface area for leaching.
Initial Boil: Place the cut potatoes in a large pot of water. Bring the water to a boil and cook for about 8-10 minutes.
Drain and Discard: Drain the potatoes completely and discard the cooking water, which now contains a portion of the leached potassium.
Soak (Optional but Recommended): Place the parboiled potatoes into a fresh pot of warm water and soak for a minimum of two hours, or up to 12 hours for maximum effect. Change the water every few hours if soaking for a longer period.
Final Cooking: Drain the soaked potatoes and cook them as desired (boil again in fresh water, mash, roast, or fry).

It is important to remember that boiling also removes other water-soluble nutrients, such as vitamin C and B vitamins. For individuals who do not need to limit potassium, cooking potatoes with less water (like baking or microwaving) and eating the skin is the most nutrient-preserving method. Always consult with a dietitian to create a plan that fits your specific health needs.

For more detailed guidance on dietary management for kidney health, authoritative sources like the National Kidney Foundation offer valuable resources on potassium and your diet.

Conclusion

Boiling is an effective culinary method for removing a significant amount of potassium from potatoes, making them a more suitable option for those with chronic kidney disease or other conditions requiring a low-potassium diet. While simple boiling can remove a moderate amount, techniques like double-boiling and the boil-and-soak method can achieve far more substantial reductions. The key is to maximize the surface area by peeling and cutting the potatoes, and always discarding the potassium-rich cooking water. By understanding and applying these techniques, individuals can safely incorporate potatoes into a balanced, kidney-friendly diet while managing their mineral intake effectively.

Frequently Asked Questions

No, studies show that soaking raw, fresh potatoes does not significantly reduce their potassium content. A much greater reduction is achieved by soaking the potatoes after they have been boiled.

Yes, canned potatoes are a good option as they have already undergone a leaching process. Rinsing canned potatoes can further reduce their potassium content, and soaking them can achieve even lower levels.

For those on a renal diet, the boil-and-soak method is the most effective. This involves peeling and cutting the potatoes, boiling them briefly, draining the water, and then soaking them in fresh water for at least 12 hours before a final cook.

Yes, cutting potatoes into smaller, thinner pieces (e.g., strips, dice, or shredded) is crucial for effective potassium removal. A larger surface area allows more of the mineral to leach into the boiling or soaking water.

Prepared correctly, boiled potatoes can be part of a kidney-friendly diet. The potassium content can be significantly lowered using techniques like double-boiling or the boil-and-soak method. Always consult with your dietitian for personalized dietary advice.

No, baking or microwaving potatoes does not effectively remove potassium, as there is no water for the mineral to leach into. In fact, these methods can even concentrate the nutrients, including potassium, on a per-gram basis due to water loss.

The cooking water from boiled potatoes contains the potassium that has been leached out. For those on a low-potassium diet, it is very important to discard this water and not use it for sauces, gravies, or soups.