We all know that vegies are good for us. But you may be surprised to learn that the way you cook your vegetables might not deliver the most nutrients. Read on to find out how to get the most nutritional goodness from your vegies.
While most vegies are extremely versatile, the method you use to cook them can actually make a significant difference to the amount of nutrients you’ll receive when you eat them. Each type of coloured vegetable (even the brown/white colour group, including onions, parsnips, cauliflower, mushrooms and potatoes) offers a unique blueprint of nutrients and phytochemicals, all of which play essential roles in maintaining a healthy body.
Some vegies should be eaten raw or cooked in a way that minimises the loss of water-soluble vitamins – such as vitamin C and the B group vitamins – which can be destroyed by heat. Other vegetables, like potatoes, need to be well cooked to get the maximum benefit from specific phytonutrients. For these vegetables, cooking ruptures the plant cells and allows the nutrients to be more readily available when digested. Follow our guide to get the most nutrition out of your vegetables.
Brassicas, such as cauliflower, cabbage, broccoli and broccolini, are high in vitamin C, folate, iron, calcium, selenium, fibre and antioxidants. These vegies pack their biggest nutritional punch via steaming, which offers the best retention of vitamin C and iron.Steam over a pot of simmering water for as little time as possible – vegies should still be brightly coloured and have an audible crunch. Microwave steaming preserves slightly more nutrients – use as little water as possible and microwave on high for five minutes or less.
Stir-frying is another great option for brassicas, but make sure you cook with a spray oil – using water to stir-fry actually increases nutrient loss.
Brassicas can also be enjoyed raw, however they do contain goitrogenic compounds. If eaten in excess, the goitrogens in raw brassicas could potentially cause problems for those with poor thyroid function and may lead to the formation of goitres. These compounds are destroyed by heat, however, so a light stir-fry or steam is the best bet.
Leafy greens like spinach, silverbeet and watercress are great sources of vitamins A, C, E, folate, calcium and iron. Leafy green vegetables make lovely salads and without heat their nutritional value is maximised.
Quickly stir-frying or stirring leafy greens through a hot dish is also a great way to get the most from these vegies. The leaves should stay dark green, and only just begin to wilt. Avoid cooking leafy greens in water, as many of the water-soluble vitamins are washed away with the green water. Like brassicas, these vegies are also suited to microwave steaming with little or no water.
Bok choy, gai laan, mustard cabbage and wombok are rich in carotenoids (phytochemicals and antioxidants that can protect against certain cancers and cellular damage). They also contain vitamin C and antioxidants and most varieties of Asian greens are good sources of iron. When it comes to eating these versatile vegies, wombok is delicious and at its most nutritious when eaten raw. The baby or inner leaves of most other Asian greens can also be eaten raw. Steaming is also a good option. Add Asian greens to a stir-fry in the last minute or two of cooking: the leaves should stay green and wilt slightly, while the stems remain firm with a bit of crunch.
Fresh or frozen peas and green beans
Peas and green beans are good sources of key nutrients including folate, vitamins A and C, fibre and carotenoids. Fresh beans and peas can be eaten raw and will offer the most nutrition. Frozen vegetables should not be eaten raw by pregnant women to reduce the risk of food poisoning, but for most people, there is no problem in doing so. Frozen vegetables are blanched prior to freezing, so they need even less cooking time than fresh vegetables.
Steaming for just a few minutes is the best way to retain nutrients. Beans and peas should remain bright green, slightly crunchy and wrinkle-free. Another good way to retain nutritional goodness is by stir-frying them quickly from frozen.
Potatoes and sweet potatoes (kumara) are popular vegies due to their versatility and delicious flavour – but any method of cooking that involves lots of oil and salt isn’t going to yield the most nutritional benefits.
Sweet potato is a good source of vitamin C, calcium, iron and potassium, and potato provides both vitamin C and potassium. Since water-soluble vitamins are lost through boiling, steaming is the best way to go. Wash potatoes and pierce them a few times with a fork before cooking. If microwave steaming, wrap them in a damp paper towel after piercing and cook for several minutes, until they are soft.
Tubers can also be baked in their skins until the flesh is nice and soft. Unlike many green vegetables, tubers need to be cooked before eating to improve the digestibility of the starches.
Coloured root vegetables
Carrots and beetroots are distinctly flavoured and always lend a beautiful splash of colour to a plate. To reap the key nutritional benefits of the beta carotene (vitamin A), vitamin C, fibre and antioxidants in these vegies, they need to be treated right. Beta carotene is made more readily available by puréeing or mashing, and is absorbed more easily when combined with oil. Stir-frying quickly in a small amount of good quality oil will help retain heat-fragile vitamins and antioxidants. You could also spray lightly with oil and roast both beetroots and carrots, or grate them when raw to create antioxidant-rich salads.
Although technically a fruit, tomatoes are often viewed and used as a vegetable. They are rich in lycopene, carotenoids, vitamin C and fibre. In order to increase the bioavailability of lycopene and carotenoids, lightly sauté or roast tomatoes in a little oil. The skins will wrinkle, the colour will deepen and the sweetness will intensify. Use them as a side dish to accompany meat dishes, or turn them into sauces or pastes.
Of course, raw tomato is a popular and nutritious addition to most salads. It’s a good source of vitamin C when raw, but it’s not the nutritional powerhouse it is when cooked.
To extract the most folate, fibre and antioxidants from eggplant, slice it lengthways, spray lightly with oil and grill until slightly softened. Avoid charring it and make sure you leave the antioxidant-rich purple skin on. Alternatively, roast them gently, then purée (with the skin on for maximum nutrition) with garlic, tahini, lemon juice and olive oil to make baba ganoush. Eggplant is not usually eaten raw since the flesh is bitter and fibrous unless cooked.
Zucchini’s key nutrients are folate, beta carotene and fibre. Steaming will preserve the most nutrition: steam briefly to retain firmness and the bright green skin. Stop steaming as soon as the centre flesh turns translucent and the seeds become more visible.
Other good ways to preserve zucchini’s nutrients include stirfrying quickly in a spray of oil or grating into other dishes – try making savoury pancakes by grating a small zucchini into the batter. Raw zucchini can also be shredded or grated and used in salads or sandwiches.
Bright and beautifully coloured, capsicum is rich in carotenoids, vitamin C and fibre. To maximise these nutrients, slice capsicums into large pieces to reduce vitamin loss while cooking and stir-fry for less than three minutes in a teaspoon of oil. The skin should remain bright, firmly attached and slightly crunchy. Alternatively, grill capsicum halves for a few minutes, peel off the skin and dress the flesh with olive oil and balsamic vinegar.
Raw capsicum is packed with readily-available vitamin C – add it to salads or sandwiches or dip into low-fat hommous.
Cooking methods at-a-glance
This is a great way to cook because it minimises the loss of nutrients from vegetables. There are two types of steaming methods: using a steamer placed over boiling water or using a microwave (see below).
HFG tip: Resist the temptation to cook vegetables too long. Perfect steamed vegies are brightly coloured and tender-crisp, rather than mushy.
This is one of the fastest ways to cook and steam vegetables. When it comes to steaming, microwaving is the best method because you lose slightly less nutrients due to the quick cooking time.
HFG tip: Don’t microwave food in ice-cream and margarine containers – they’re high in PVC and may pass plastic molecules into your food when they’re heated. Use containers designed for microwave use, such as treated plastic, glass, ceramic or paper. Cover vegies with a lid or plastic wrap (pierced). Never put metal containers or aluminium foil into the microwave.
Chargrilling and barbecuing
These cooking methods enrich the flavour of eggplant and capsicum.
HFG tip: Use a small spray of cooking oil to avoid the ‘stick factor’. When barbecuing or chargrilling, lightly spray the food, rather than the barbecue plate or chargrill pan, with oil. This will prevent the barbecue from smoking.
This simple, low-maintenance cooking method is another healthy way to get the most out of vegies like starchy tubers or coloured root vegetables – just watch the oil!
HFG tip: Make homemade chips: thinly slice potatoes, sweet potatoes or carrots and place on a baking tray lined with baking paper. Spray your vegies with a little oil, then roast until golden and tender.
The fast cooking time involved with stir-frying means more nutrients are retained. Simply spray a hot wok or frying pan with oil and add vegies, such as carrot and capsicum.
HFG tip: A bag of frozen ‘stir-fry mix’ vegetables is a great stand-by for nights when you don’t have the time or energy to cook. Simply stir-fry and serve with meat and noodles or rice.
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