The World's Healthiest Foods

Does covering the pot when making soup help to preserve nutrients?

Yes, it is helpful to cover your soup pot when making soup. The process of soup-making exposes food to increased temperatures over a relatively long period of time. In addition, foods are usually chopped up or sliced before being added to a soup, and this chopping and slicing increases their exposed surface area. Finally, these chopped and sliced foods with more exposed surface areas get submerged into water. This particular combination of factors—large food surface areas exposed to water under increased temperature for an extended period of time—is a perfect combination for leaching water-soluble nutrients from food.

This leaching doesn't happen all at once. But over the time it takes to cook a soup, some water-soluble nutrients (including B-vitamins and vitamin C) will be drawn out of the food and into the broth. There will still be important amounts of water-soluble nutrients left in the food, but a varying percentage of these nutrients will have migrated into the broth.

From among the water-soluble nutrients that have migrated into the broth, some will become volatile and evaporate in the steam that rises from the soup pot. These nutrients will be lost into the air. By covering your soup pot, you will create a mechanical barrier that will trap some of these volatile nutrients and cause them to fall back down into the broth. In this way, your soup broth will stay more nutrient-rich. In comparison to an opened soup pot without a lid, you'll need to turn down your stove burner to achieve a gentle simmer when you're making soup in a covered pot.