SUMMER is upon us which means it’s salad season.
When it’s too hot to cook, a leafy salad of chopped fresh vegetables is easy.
If you’re already getting these foods into your diet, great for you!
But Laura Brown, a senior lecturer in Nutrition, Food, and Health Sciences, Teesside University, has shed some fascinating light on why they are best eaten cooked.
She said raw food diets are a fairly recent trend. It holds the belief that the less processed food is, the better.
“However, not all food is more nutritious when eaten raw,” Ms Brown wrote in a piece for the Conversation.
“Indeed, some vegetables are actually more nutritious when cooked.”
Some vegetables are so versatile they can be eaten raw or thrown into pretty much any curry, stew or soup, or in an omelette, for example.
But be mindful how you cook it, as Ms Brown said the higher the temperature, cooking time and amount of water, the more nutrients will be lost.
Vitamins can be lost in cooking water, which is why experts recommend steaming or roasting veg over boiling.
Ms Brown laid out nine foods that are best served cooked and why:
Ms Brown said: “Spinach is rich in nutrients, including iron, magnesium, calcium and zinc.
“However, these nutrients are more readily absorbed when the spinach is cooked.
“This is because spinach is packed with oxalic acid (a compound found in many plants) that blocks the absorption of iron and calcium.
“Heating spinach releases the bound calcium, making it more available for the body to absorb.
Research also suggests that steaming spinach maintains its levels of folate (B9), which may reduce the risk of certain cancers, Ms Brown said.
Tomatoes – you either love them grilled or cold.
“Cooking, using any method, greatly increases the antioxidant lycopene in tomatoes,” said Ms Brown.
“Lycopene has been associated with a lower risk of a range of chronic diseases including heart disease and cancer.
“This increased lycopene amount comes from the heat that helps to break down the thick cell walls, which contain several important nutrients.”
But as a pay off for increasing lycopene, cooking tomatoes does reduce vitamin C content by 29 per cent.
Grated carrot is a staple of coleslaw – and always raw.
Ms Brown said cooked carrots, however, “contain more beta-carotene than raw carrots, which is a substance called a carotenoid that the body converts into vitamin A”.
Vitamin A supports bone growth, vision and the immune system.
Ms Brown also had some cooking tips to boost the carrot’s true potential.
“Cooking carrots with the skins on more than doubles their antioxidant power,” she said.
“You should boil carrots whole before slicing as it stops these nutrients from escaping into the cooking water. Avoid frying carrots as this has been found to reduce the amount of carotenoid.”
4. Bell peppers
Peppers are delicious both cooked and raw.
But to keep their high antioxidant properties, which boost the immune system, throw your peppers into a hot dinner instead.
Ms Brown said: “All living things are made up of cells, and in vegetables, important nutrients are sometimes trapped within these cell walls”.
But heat “breaks down the cell walls, making the carotenoids easier for your body to absorb”.
She added: “As with tomatoes, vitamin C is lost when peppers are boiled or steamed because the vitamin can leach out into the water. Try roasting them instead.”
Kale isn’t everyone’s cup of tea, but for those that love it, it’s often the bed for a salad.
Ms Brown said: “Kale is healthiest when lightly steamed as it deactivates enzymes that prevent the body from using the iodine it needs for the thyroid, which helps regulate your metabolism.”
Asparagus, believe it not, can be eaten raw as well as cooked.
But you’re better sticking to the latter, as Ms Brown explains: “When vegetables are cooked, the walls break down, releasing the nutrients that can then be absorbed more easily by the body.
“Cooking asparagus breaks down its cell walls, making vitamins A, B9, C and E more available to be absorbed.”
If cooked mushrooms in your diet, you may be keen to add them after hearing their key benefits.
Ms Brown said: “Mushrooms contain large amounts of the antioxidant ergothioneine, which is released during cooking.
“Antioxidants help break down ‘free radicals’, chemicals that can damage our cells, causing illness and ageing.”
An anti-ageing ingredient that can be added to almost anything – from stir frys, bolognese, currys and omelettes? Yes please.
8. Green beans
Green beans are an easy veg to add to almost any dish.
But the way you cook them could have a big impact on the vitamins you absorb from them.
“Green beans have higher levels of antioxidants when they are baked, microwaved, griddled or even fried as opposed to boiled or pressure cooked,” Ms Brown said.
Brassica, which include broccoli, cauliflower and brussels sprouts, have anti-cancer properties.
They contain glucosinolates which the body can convert into a range of cancer-fighting compounds.
But there’s only one way to cook them if you want to reap the rewards, Ms Brown suggests.
“For these glucosinolates to be converted into cancer-fighting compounds, an enzyme within these vegetables called myrosinase has to be active,” she explained.
“Research has found that steaming these vegetables preserves both the vitamin C and myrosinase and, therefore, the cancer-fighting compounds you can get from them.”
She added: “Chopping broccoli and letting it sit for a minimum of 40 minutes before cooking also allows this myrosinase to activate.”
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