How to lower the potassium in food: the double-cooking technique

Some vegetables and root vegetables you love, like the potato, are high in potassium. The good news: there is a simple technique, double cooking, that removes a good part of that potassium and lets you enjoy them again more safely.

Why does double cooking work?

Potassium is water soluble: when you soak and boil the food, part of the potassium passes into the water. If you discard that water, you discard that potassium. The smaller the cut and the longer the soak, the greater the reduction.

Double cooking step by step

1. Peel and cut the food (potato, sweet potato, carrot) into small pieces. The smaller, the better.
2. Soak in plenty of warm water for at least 2 hours (ideally overnight).
3. Discard that soaking water.
4. Boil in fresh water until tender.
5. Discard the cooking water too before serving or preparing.

Other tricks to reduce potassium

• Cut thinner: more surface in contact with water = more potassium released.
• Change the water twice during cooking for foods very high in potassium.
• Avoid steaming or microwaving high-potassium foods: they retain the mineral. Boil and discard the water instead.
• Do not reuse the cooking water for soups or stews: that is where the potassium went.

Double cooking is a valuable tool, but it does not replace portion control or your nephrologist's advice. Use it to widen your options, not to eat without limits.

Read also: How to control phosphorus · Common mistakes in the kidney diet