Question:
I enjoy broccoli, either raw in salads or lightly cooked in the microwave. Is there a difference in the nutrition between the raw and the lightly-cooked vegetable?
Answer:
Broccoli was voted New Zealanders’ second-most favourite vegetable in 2023′s inaugural VegElection, hot on the heels of tomato – which technically is a fruit. But semantics aside, our love affair with broccoli brings many benefits.
Broccoli belongs to the brassica family of vegetables, joining cauliflower, cabbage, Brussels sprouts, broccoflower and various Asian cabbages. Native to the eastern Mediterranean and Asia Minor, broccoli was cultivated in Italy and reportedly introduced to England and America in the 1700s. But it became a commercially grown crop in New Zealand only in the 1970s.
It’s hard to believe this now-favourite vegetable is a relative newcomer. But thank goodness broccoli is here because it is incredibly versatile and is packed with helpful nutrients – one serving (about half a cup or 80g) provides our entire daily vitamin C needs (45mg), as well as some vitamin A, folate, vitamins B6 and E, dietary fibre and a range of helpful dietary phytonutrients.
But what happens to those nutrients when broccoli is cooked? Generally, the fibre and fat-soluble vitamins in vegetables, such as vitamins A and E, are not significantly affected by either boiling or steaming. And the bioavailability of some nutrients, such as the lycopene found in tomatoes and the beta-carotene in carrots, may improve with cooking. A 2013 study, published in the International Journal of Food Sciences and Nutrition, found that cooking broccoli increased the apparent concentrations and ability to absorb certain healthful antioxidants and nutrients, such as lutein, beta-carotene and tocopherols (vitamin E variants).
However, broccoli also contains water-soluble vitamins and phytochemicals. And these nutrients are readily lost through leaching when vegetables are immersed in water during certain cooking processes.
Light, heat and air easily damage vitamin C, so food handling, preparation, and cooking processes will influence the vitamin C content of broccoli and other vitamin C-rich foods. Everything from shelf-time to storage time, cutting, bruising, heating and exposure to iron and copper, as well as leaching from foods into cooking water, can reduce the vitamin C content.
A 2009 study investigated the impact of steaming, microwaving, boiling and stir-frying on the nutrient content of broccoli. It found all cooking treatments, except steaming, caused significant vitamin C losses. Steaming also reduces losses of glucosinolates, the sulphur-containing compounds found in broccoli that are credited with protecting us from cancer and cardiovascular disease.
In contrast, a 2018 study found microwaved broccoli retained more vitamins than blanching, steaming or boiling. The difference was that the 2018 study microwaved the broccoli for less time and steamed the broccoli for twice as long as the 2009 study – explaining why the two studies had conflicting results.
These two studies reveal a clear pattern: the shorter the cooking time, the greater the retention of vitamin C, regardless of the cooking method.
Other factors also reduce losses of vitamin C and other water-soluble vitamins, such as using less water in cooking and leaving the broccoli or other vegetables as intact as possible.
But it’s worth remembering that while cooking methods and other factors influence the retention of water-soluble vitamins, broccoli’s fibre and fat-soluble vitamins and antioxidants aren’t significantly affected by cooking and some may increase in bioavailability.
Ultimately, only two-thirds of New Zealand adults eat the recommended three servings of vegetables daily. So whether you enjoy your broccoli cooked or raw, you are opting for a nutritious, delicious food that’s good for your health.
The best vegetable for you is the vegetable you will eat rather than leave languishing in your fridge. So broccoli is a great option whether it’s raw, stir-fried, roasted, steamed or microwaved.
