Do Vegetables Lose Vitamins When Cooked?

To get the most out of the veggies you consume, it pays to learn the best ways to prepare them. Learn more about how these 11 cooking methods may impact the potency of the vitamins and minerals found in fresh produce. That said, eating veggies in almost any form — battered and deep fried is one exception — is much healthier than leaving them off your plate.

• Fiber
• Calcium
• Potassium
• Magnesium
• Vitamin A
• Vitamin C
• B vitamins
• Iron
• Vitamin K
• Vitamin E

“Fresh and cooked vegetables both play an important role in a balanced diet,” says Sharniquia White, RDN, a trained chef and nutrition expert in Greensboro, North Carolina. “Raw vegetables often provide the highest levels of heat-sensitive vitamins like vitamin C and some B vitamins, while cooking can enhance the absorption of others, like vitamin A.”

Longer cooking times for veggies can reduce the nutritional quality, but some veggies are also more susceptible to nutrient changes from cooking than others.

Vegetables That Tend to Lose More Nutrients When Cooked

Some vegetables that are likely to be negatively impacted by cooking include:

• Broccoli and spinach: These tend to lose vitamin C.

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• Greens like chard, crown daisy, and mallow: Research shows that cooked greens often lose vitamin K.

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• Potatoes, sweet potatoes, and carrots: These root veggies may lose vitamin E with cooking.

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Vegetables With Higher Nutrient Bioavailability After Cooking

On the other hand, cooking gives some veggies a boost in nutritional bioavailability. Here are some vegetables that may be enhanced by cooking.

• Tomatoes By breaking down plant cell walls, cooking increases the bioavailability of beta-carotene in carrots and lycopene in tomatoes, says Karolin Saweres, RDN, the founder of My Nutrition and Me, a weight management and disease prevention practice based in Cincinnati.

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• Asparagus Cooking asparagus increases its levels of antioxidant phenolic compounds.

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• Mushrooms Microwaving or grilling mushrooms may enhance their antioxidant activity, too.

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• Carrots Though some nutrients in carrots may decrease with cooking, others may be enhanced. The body more easily uses beta-carotene from cooked carrots than raw ones.

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Here’s what to know about each cooking method.

Boiling

“If you do decide to boil your veggies, pairing the method with a shorter cook time or repurposing the cooking liquid can help mitigate nutrient loss,” Leverich says.

Steaming

“Compared to boiling, steaming tends to retain more antioxidants and natural color — a good visual cue that nutrients are still intact,” she says.

Microwaving

The microwave isn’t best known as the kitchen device for healthy meal prep, but as it turns out, this quick-cook kitchen staple is surprisingly good at retaining the nutrients found in vegetables.

“Microwaving consistently ranks as one of the best methods for retaining nutrients in vegetables,” Leverich says. “Its rapid cooking time and minimal water use help protect heat- and water-sensitive vitamins.”

Sautéing and Stir-Frying

Sautéing uses medium heat to cook foods, while stir-frying uses higher heat. When the amount of oil you add is kept in check (think a 1 tablespoon serving of olive oil or less), White says both cooking methods are great for preserving nutrition.

Grilling and Broiling

Though grilling uses high heat, this cooking style is less likely to leach the healthy compounds out of your veggies than some other options.

Broiling also exposes foods to a strong heating element, which can be beneficial for some types of veggies and less so for others. While broiling does not involve water, its intense heat can break down water-soluble vitamins such as C and some B vitamins, Leverich says.

Baking and Roasting

Despite the higher temps used to heat veggies in the oven, this method doesn’t excessively diminish veggies’ nutrient density, says Saweres.

“Baking and roasting are generally favorable because they use dry heat and little to no added water, which helps limit nutrient leaching,” says Saweres. Plus, baking and roasting can bring out vegetables’ inherent sweetness, often helping people enjoy them more, she says.

While some vitamin C loss will occur in a hot oven, Saweres says fat-soluble antioxidants, like carotenoids in carrots, may become more bioavailable. This is especially true when roasted vegetables are paired with healthy fats like olive or avocado oil.

Pressure Cooking and Slow Cooking

Pressure cooking and slow cooking both use small appliances — sometimes the same device — to heat foods to doneness. But the two have different effects on veggies’ nutrition.

The gradual process of slow cooking, on the other hand, isn’t as beneficial for nutrition.

“Slow cooking involves longer exposure to heat, which may reduce water-soluble vitamins, though minerals and fiber remain largely intact,” says Saweres. She says to use minimal liquid in the slow cooker to improve nutrient retention.

Even if some nutrients are lost during cooking, veggies are still a healthy food choice. Try these tips to preserve the vitamins and minerals they contain.

1. Use minimal water. “Microwaving and grilling are great examples — they use little to no water and cook fast, which helps preserve vitamins,” says Leverich.
2. Skip the veggie peeler. Fiber, vitamin A, vitamin K, potassium, and other nutrients are abundant in many veggies’ peels. “Keep the skins on when you can. Nutrients live there!” says White.

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3. Cook them quickly. Long simmering times tend to pull nutrition out of vegetables, so choose the methods that keep cook times short.
4. Cut veggies into large pieces. Saweres says this reduces the likelihood of nutrient losses, since it exposes less surface area.
5. Add a source of fat. Vitamins A, D, E, and K need a source of fat for absorption. White suggests adding a healthy oil — think olive or avocado — to veggies.
6. Reuse cooking water. If you are boiling or slow cooking, don't toss that excess liquid. “Use it in a soup or sauce so those water-soluble vitamins make their way back onto your plate,” Leverich says.

• Both raw and cooked veggies are packed with nutrients, but heating veggies can have an impact on the concentration of vitamins and minerals they contain.
• Quick-cooking techniques that use little to no water, such as grilling, microwaving and stir-frying with healthy oils, can improve the bioavailability of some nutrients.
• Help preserve nutrients by keeping veggies’ skins on, cutting them into larger pieces, and reusing cooking water as a base for soups or sauces.