Recent raw food diet trends ignore the fact that some vegetables are more nutritious when cooked. Cooking methods such as steaming or roasting can increase the availability of key nutrients in vegetables such as asparagus, mushrooms and spinach. This process releases important vitamins and antioxidants that are sometimes trapped in the vegetable’s cell walls. Although cooking can reduce some vitamins, such as vitamin C, the overall absorption of nutrients is often increased, which promotes immune function, bone growth, and cancer prevention.
Cooked vegetables, including asparagus, mushrooms and spinach, often provide more nutrients than raw, as cooking releases essential vitamins and antioxidants to improve health.
Raw food diets are a fairly new trend, including raw veganism. Arguably, the less processed food, the better. However, not all foods are more nutritious when eaten raw. Indeed, some vegetables are actually more nutritious when cooked. Here are nine of them.
1. Asparagus
All living things are made up of cells, and important nutrients in vegetables are sometimes trapped in the walls of these cells. When vegetables are cooked, the walls break down, releasing nutrients that can then be more easily absorbed by the body. Cooking asparagus breaks down its cell walls, making vitamins A, B9, C and E more available for absorption.
When asparagus is cooked, its cell walls break down, releasing an abundance of nutrients that are otherwise hard to access. This process makes vitamins A, B9 (folate), C and E more available for absorption. These vitamins play a critical role in maintaining immune health, skin health, and cellular function.
2. Mushroom
Mushrooms contain a large amount of the antioxidant ergothioneine, which is released during cooking. Antioxidants help break down “free radicals,” chemicals that can damage our cells, causing disease and aging.
3. Spinach
Spinach is rich in nutrients, including iron, magnesium, calcium and zinc. However, these nutrients are more easily absorbed when spinach is cooked. This is because spinach is loaded with oxalic acid sour (a compound found in many plants) that blocks the absorption of iron and calcium. Heating the spinach releases the bound calcium, making it more available for the body to absorb.
Research shows that steaming spinach preserves folate (B9) levels, which may reduce the risk of certain types of cancer.
Cooked tomatoes are a source of nutritional energy, mainly due to the significant increase in lycopene, a powerful antioxidant, when they are heated. Lycopene has been linked to a reduced risk of chronic diseases, including heart disease and certain types of cancer. While cooking tomatoes reduces vitamin C content, the overall increase in bioavailable nutrients, especially lycopene, outweighs the loss.
4. Tomato
Cooking, using any method, greatly increases the tomato’s antioxidant lycopene. Lycopene has been linked to a lower risk of several chronic diseases, including heart disease and cancer. This increased amount of lycopene comes from heat, which helps break down the thick cell walls that contain several important nutrients.
Although cooking tomatoes reduces vitamin C content by 29%, lycopene content increases by more than 50% within 30 minutes of cooking.
5. Carrot
Cooked carrots contain more beta-carotene than raw carrots, a substance called a carotenoid that the body converts to vitamin A. This fat-soluble vitamin supports bone growth, vision, and the immune system.
Cooking carrots with their skins more than doubles their antioxidant power. You should cook the carrots completely before slicing them, as this will stop these nutrients leaching into the cooking water. Avoid roasting carrots, as this has been found to reduce carotenoid levels.
Bell peppers undergo a transformation when cooked that increases the availability of certain nutrients. Cooking breaks down their cell walls, making carotenoids like beta-carotene, beta-cryptoxanthin and lutein more absorbable. These antioxidants are vital for maintaining eye health and maintaining the immune system.
6. Bell pepper
Bell peppers are an excellent source of immune-boosting antioxidants, especially the carotenoids beta-carotene, beta-cryptoxanthin, and lutein. Heat breaks down cell walls, making it easier for your body to absorb carotenoids. As with tomatoes, vitamin C is lost when peppers are cooked or steamed, as the vitamin can leach into the water. Try frying them instead.
7. Brassica
Brassicas, which include broccoli, cauliflower, and Brussels sprouts, are rich in glucosinolates (sulfur-containing phytochemicals) that the body can convert into a variety of cancer-fighting compounds. In order for these glucosinolates to be converted into cancer-fighting compounds, an enzyme in this vegetable called myrosinase must be active.
Studies have shown that steaming these vegetables preserves both vitamin C and myrosinase, and thus the cancer-fighting compounds you can get from them. Chopping broccoli and letting it sit for at least 40 minutes after cooking allows this myrosinase to be activated.
Similarly, sprouts, when cooked, produce indole, a compound that may reduce the risk of cancer. Cooking the sprouts also causes glucosinolates to break down into compounds known to have cancer-fighting properties.
Cooking green beans can increase their nutritional value, especially in terms of antioxidant content. Various cooking methods such as baking, microwaving, and grilling have been shown to increase the antioxidant levels of green beans compared to boiling or pressure cooking. These antioxidants play a crucial role in protecting the body from oxidative stress and inflammation.
8. Green beans
Green beans are higher in antioxidants when they are baked, microwaved, grilled or even fried as opposed to boiled or pressure cooked.
9. Kale
Cabbage is healthiest when lightly steamed because it disables the enzymes that prevent the body from using the iodine needed by the thyroid gland to help regulate metabolism.
For all vegetables, higher temperatures, longer cooking times, and higher amounts of water result in more nutrient loss. Water-soluble vitamins (mostly C and B vitamins) are the most volatile nutrients when it comes to cooking because they leach out of vegetables into the cooking water. So avoid soaking them in water, use minimal amount of water when cooking and use other cooking methods like steaming or grilling. Also, if you have leftover cooking water, use it in soups or sauces as it retains all the leached nutrients.
Written by Laura Brown, Senior Lecturer in Nutrition, Food and Health Sciences, University of Teesside.
Adapted from an article originally published on The Conversation.
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