If you've ever wondered if cooking vegetables removes nutrients, you're not alone. The short answer is yes, but it gets more complicated depending on the method you choose.
To better understand how vegetables lose nutrients when cooked, it's important to look at each cooking method and how it affects the nutrient composition of food.
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Some methods of cooking cause vegetables to lose more nutrients during preparation than others.
How Cooking Affects Vegetable Nutrition
The way you cook and prep vegetables plays a role in how nutritious the vegetables are when eaten, according to an April 2016 review in the International Journal of Gastronomy and Food Science.
But, even though vegetables lose some nutrients when cooked, that doesn't mean you should only eat them raw. Cooking vegetables can actually be pretty beneficial, according to the Food Revolution Network.
For one, when you cook vegetables, it can actually enhance the absorption of nutrients that are otherwise difficult for your body to process in a raw form — such as beta-carotene (which is important for the skin), lutein (which plays a role in eye health), calcium (which is essential for bone health) and lycopene (which is associated with protection against heart disease cancer).
Adding more vegetables to your diet is a great way to increase the variety of nutrition that you receive from food. By varying the way you cook your vegetables, you can ensure that you're getting enough of the nutrients your body needs.
Boiling, Blanching and Steaming
Boiling, blanching and steaming are all water-based methods of cooking. Boiling involves submerging the vegetables completely in boiling water for a few minutes. Blanching involves briefly boiling or steaming the food for just a few seconds, then submerging the food in iced water or cold running water to stop the cooking process. Steaming involves cooking the vegetables using steam heat.
Water-based methods of cooking like these result in the loss of nutrients that are water-soluble, like vitamin C and B vitamins — but these methods are not created equal.
Vitamin C is lost during boiling more than any other cooking method. In fact, broccoli, spinach and lettuce may lose up to 50 percent of the vitamin C in them when boiled, according to August 2009 research in the Journal of Zhejiang University.
With blanching, some vitamin C is lost in the process, but it is less than boiling since the cooking time is shorter. Blanching also helps slow down the loss of other vitamins and minerals in vegetables, according to the Academy of Nutrition and Dietetics. Blanching may even help stop enzyme activity that causes your produce to spoil, and it cleans the veggies of dirt and some bacteria that could harm your health.
Steaming is considered one of the best ways to preserve and enhance the nutrients in veggies, even the water-soluble nutrients, as the food isn't totally submerged in water. For example, steaming broccoli, spinach and lettuce may only lower their vitamin C content by 9 to 15 percent, according to September 2013 research in Nutrition and Food Science.
Roasting and Grilling
Roasting and grilling your vegetables are great ways to prepare them because they are cooked using dry heat (either the oven or the grill) and there's no need to add fats like butter or oil, according to the Mayo Clinic.
Though the heat will still cause some nutrient loss, these methods will preserve more of the water-soluble nutrients like vitamin C and B vitamins, than boiling.
Sautéing and Stir-Frying
Sautéing and stir-frying are both done on the stove over medium to high heat. The difference is that during stir-frying, the food is constantly stirred at a higher heat for a shorter amount of time.
Both of these methods of cooking vegetables are considered healthy by the Mayo Clinic. And because they don't involve using water, the water-soluble vitamins are mostly retained during cooking.
On top of that, some research shows that cooking veggies this way may actually improve your ability to get nutrients from them. For example, people were 6.5 times more able to absorb beta carotene — an antioxidant — from stir-fried carrots compared to raw ones, according to a May 2012 study in the British Journal of Nutrition.
It's believed that the addition of fats from cooking oil enhances our ability to absorb these nutrients, per October 2017 research in the American Journal of Clinical Nutrition.
Microwaving vegetables like potatoes is a popular way to cook them because it's convenient and doesn't take a lot of time. Many people worry that microwaving destroys nutrients in vegetables, but that isn't the case.
When using the microwave, you are able to cook your vegetables for a shorter amount of time with less heat, which actually leads to less nutrient loss than other high-heat cooking methods like boiling, according to Harvard Health Publishing.
That being said, the way you cook your vegetables in the microwave matters. Submerging the veggies in water and microwaving them may cause vitamin C to leech out into the water, while steaming them in a steamable bag may preserve nutrients, per Harvard Health Publishing.
And for those who are wondering if it is safe to microwave potatoes, the answer is yes. Nuking your potato, or any other veggie, won't make it radioactive. A microwave is a source of non-ionizing radiation, which is not the same kind of radiation as produced by an X-ray machine.
Microwaved potatoes and vegetables are still nutritious because microwaving does not change their chemical structure, and food does not retain microwaves or radiation after cooking, per the American Society of Clinical Oncology.
The Bottom Line
All cooking methods result in some loss of nutrients, but that isn't always a bad thing. When you want to preserve or enhance the absorption of nutrients in your vegetables, it's important to know that the way you cook them can greatly affect their benefits.
Research shows that boiling vegetables in water leads to the most nutrient loss, particularly of water-soluble vitamins. Blanching and steaming, though they involve water, lead to less nutrient loss than boiling.
If you find yourself stocking up on frozen vegetables to help meet your nutritional quota, keep in mind that steamable microwave bags are your best bet when it comes to cooking them. Cooking in steamable bags may increase the antioxidant activity of your vegetables, according to an October 2015 study in the Journal of Innovative Food Science & Emerging Technologies.
On the other hand, sautéing and stir-frying your veggies in healthy fats like olive oil or avocado oil may help you absorb key antioxidants, too. Dry methods of cooking like roasting and grilling veggies are also fine options.
- International Journal of Gastronomy and Food Science: “A Review of the Impact of Preparation and Cooking on the Nutritional Quality of Vegetables and Legumes”
- Food Revolution Network: “Raw vs. Cooked: The Healthiest Way to Eat Your Veggies”
- Health Science Academy: “Raw or Cooked Food: Which Option Grants More Nutrients?”
- Journal of Innovative Food Science & Emerging Technologies: “Effect of Steamable Bag Microwaving Versus Traditional Cooking Methods on Nutritional Preservation and Physical Properties of Frozen Vegetables: A Case Study on Broccoli (Brassica oleracea)”
- American Journal of Lifestyle Medicine: “Nutrition and Cost Comparisons of Select Canned, Frozen, and Fresh Fruits and Vegetables”
- Journal of Zhejiang University: Effects of different cooking methods on health-promoting compounds of broccoli
- Academy of Nutrition and Dietetics: Blanch Before You Freeze
- Nutrition and Food Science: Effects of different cooking methods on the vitamin C content of selected vegetables
- British Journal of Nutrition: The effect of food preparation on the bioavailability of carotenoids from carrots using intrinsic labelling
- American Journal of Clinical Nutrition: Modeling the dose effects of soybean oil in salad dressing on carotenoid and fat-soluble vitamin bioavailability in salad vegetables
- Harvard Health Publishing: Microwave Cooking and Nutrition
- American Society of Clinical Oncology: Can Using a Microwave Cause Cancer?