It can be easy to think that the less you do to a food, like eating vegetables raw rather than cooked, the better it is for you. But a nutritionist has revealed that there are lots of vegetables that become far healthier once they’ve been heated.
Laura Brown, senior lecturer in nutrition, food, and health sciences at Teesside University, wrote in The Conversation about nine vegetables that, for all vegetables, higher temperatures, longer cooking times, and larger quantities of water cause more nutrients to be lost. Water-soluble vitamins (C and many of the B vitamins) are the most unstable nutrients when it comes to cooking because they leach out of vegetables into the cooking water.
So, avoid soaking them in water, use the least amount of water when cooking, and use other cooking methods, such as steaming or roasting. Also, if you have cooking water left over, use it in soups or gravies as it holds all the leached nutrients. Brown said that important nutrients are sometimes “trapped” within cell walls. When a vegetable is cooked, these walls break down and nutrients are absorbed by the body.
Cooking asparagus breaks down its cell walls, making vitamins A, B9, C, and E more available for absorption.
Mushrooms release large amounts of the antioxidant ergothioneine during cooking. Antioxidants help break down “free radicals”, chemicals that can damage our cells and cause illness and ageing.
Spinach is rich in iron, magnesium, calcium, folate (B9), and zinc, which become more readily absorbed when the spinach is cooked.
Cooking tomatoes greatly increases their antioxidant lycopene. Lycopene has been associated with a lower risk of chronic diseases, including heart disease and cancer.
Although cooking tomatoes reduces their vitamin C content by 29%, their lycopene content increases by more than 50% within 30 minutes of cooking.
Cooked carrots contain more beta-carotene than raw carrots. The body converts this into vitamin A to support bone growth, vision, and the immune system.
Unpeeled carrots have more than double the antioxidant power of peeled carrots. Boiling carrots whole before slicing prevents nutrients from escaping into the water.
Bell peppers are a source of immune-system-boosting antioxidants, including beta-carotene, beta-cryptoxanthin, and lutein. To prevent the vitamin C from being lost in the water, peppers should be roasted rather than boiled or steamed.
Steaming brassicas (including broccoli, cauliflower, and Brussels sprouts) preserves both the vitamin C and myrosinase.
Cutting and resting broccoli 40 minutes before you cook it allows the myrosinase to activate. The enzyme allows glucosinolates to be converted into a range of cancer-fighting compounds
When cooked, sprouts also include converted glucosinolates and indole, a compound that may reduce the risk of cancer.
Green beans have higher levels of antioxidants when they are baked, microwaved, griddled, or even fried, as opposed to boiled or pressure-cooked.
Kale should be lightly steamed as this deactivates enzymes that prevent the body from using the iodine it needs for the thyroid, which helps regulate your metabolism.