Vegetables are a source of vitamins, minerals, and dietary fibers that help you stay strong and healthy. From the moment vegetables are harvested on the farm to when they’re cooked on your stove top, their nutritional value gets altered in one way or another before ending up on your dinner plate.

Of all cooking methods for vegetables, boiling is one of the ones that tends to lose the most nutrients. This is why making soup has mixed effects on the nutritional value of vegetables.

Vegetables lose nutrients when cooked in soup. Much of the nutrients dissolve in the cooking water and leach out. However, those of them that are heat stable remain in the soup. You will eat them together with the liquids.

Heat degrades some of the vitamins contained in vegetables, such as vitamin C, folate, and pantothenic acid, and strengthens others, like lycopene in tomatoes.

To get accurate information about the nutrients contained in most vegetables that you and I can buy in grocery stores, check out this section on the U.S. Food & Drug Administration’s website.

The FDA have also made neat charts for fruits and veggies that you can print out and stick on your fridge with a magnet at home.

How to Make Healthy Vegetable Soup

Here’s how to make the healthiest possible vegetable soup:

  • Add only small amounts of butter or, preferably, an alternative with less saturated fat and no cholesterol like extra-virgin olive oil to your soup;
  • Add color to your soup. Research shows that differently colored veggies have different groups of nutrients, all of which are essential to your well-being;
  • Since nutrients live near the surface of vegetables, wash the vegetable thoroughly before boiling instead of peeling the outer layer away;
  • Keep the soup at a simmer over medium heat and cook each vegetable just enough, so that it comes out soft and tender, but still firm to the bite;
  • Before serving, garnish your soup with sprouts, cilantro, and other greens since the residual heat will not affect their nutritional value.

Stop Overcooking Vegetables in Soup

One of the most common mistakes home cooks make is that they cook their veggies to mush. This not only loses most of their nutritional value, but also results in a taste and texture that aren’t really that appealing.

As with almost any food when cooking at home, the trick is often to learn how to cook vegetables just enough. Try this instead: put the vegetables that require the most cooking time first. You can add the salt and seasoning at any moment to your discretion.

For example, when I make soup with potatoes and carrots, I always boil them for 10-15 minutes first, adding other veggies like peas or broccoli after. This helps me ensure that the potatoes and carrots will come out nice and soft, but the rest of the veggies (especially the greens) won’t come out overcooked and mushy.

Add Color and Diversity to Your Soup

To make your soup healthier, make it colorful. Research shows that differently colored vegetables carry diverse groups of nutrients, all of which can contribute to your health and well-being (learn more at Harvard Health Publishing).

If you’re curious to know what color of vegetables carries which nutrients, here’s the rundown:

  • Purple and blue vegetables like kale or eggplant carry a lot of Vitamins A, C, and K. They’re also a good source of calcium and potassium.
  • Greens like Swiss chard, cabbage, or broccoli contain Vitamins A, C, and K, but also provide you with plenty of magnesium, iron, and fiber.
  • Orange and yellow veggies like potatoes and carrots carry significant amounts of Vitamins A, C, B, as well as calcium, iron, and potassium.
  • Red veggies like tomatoes, radishes, and red peppers contain lycopene, Vitamins C and A, as well as potassium and iron.
  • White and light-green vegetables like parsnip, garlic, and onions contain compounds called flavonoids, such as quercetin, kaempferol and anthoxanthins, which have a range of healthful properties.

But how do you know which vegetables to eat raw (or cooked for as little time as possible), and which ones to cook?

Here’s a useful chart to help you know how to prepare and eat some of the most commonly found vegetables at the grocery store, so that they contain the most nutrients:

VegetableHealthier IfReason Why
BroccoliRaw
(or cooked less)
Heat damages the enzyme myrosinase contained in broccoli
GarlicRaw
(or cooked less)
Heat reduces the amount of the enzyme allicin, which gives garlic its immune-boosting properties
OnionsRaw
(or cooked less)
Heat reduces the amount of phytonutrients called flavonoids in onions
CarrotsCookedCooked carrots supply your body with more of the antioxidant carotenoid
SpinachCookedCooking spinach makes the beta-carotene and iron contained in it easier for your body to digest and absorb
TomatoCookedCooking tomato increases the bioavailability of lycopene, a powerful antioxidant
How to prepare, cook, and eat vegetables at home

Does Blending Vegetables Destroy the Nutrients?

If you want to make healthier soup, should you slice the vegetables and cook them intact, or should you blend them to make cream soup?

If you blend vegetables, you won’t lose any of the nutrients contained inside them. Unlike juicing, blending grinds up the whole vegetables, including the fibers, into a smoother, but just as nutritional, consistency as the original.

To an extent, blending makes the nutrients in a vegetable soup (especially the fibers) easier for your body to digest, because it breaks down the cell walls of the plants for you.

Cream soup, however, tends to be heavier and more caloric. Many cream soup recipes call for butter, sour cream, or cheese that otherwise wouldn’t end up in your vegetable soup.

In Conclusion

The preparation of a soup has different effects on the nutritional value of vegetables. The heat of boiling or simmering water removes some nutrients from the soup. At the same time, it enhances others by making them more digestible and absorbable by the body. This is what scientists call an increase in the bioavailability of nutrients.

As long as it’s part of a balanced diet, soup can still be a great way to cook veggies in a healthy way. Yes, the cooking water washes out some of the nutrients in veggies. But unlike other cooking methods, you” actually eat them because you’re serving the soup with the cooking water.

To make the healthiest soup possible, wash the vegetables thoroughly but don’t peel them, cook them just enough so that they’re nice and soft, but not mushy, and garnish the soup with fresh greens before serving.