We all know how great vegetables are for our health (regardless of how much we might dislike them). They contain important vitamins, minerals and fibre, and a diet rich in both vegetables and fruit may help protect against cancer, diabetes and heart disease.
However, could the way we eat vegetables affect the amount of nutrients we are getting?
With social media teeming with vibrant salads and promoting raw food diets, many of us think that eating raw vegetables always trumps eating the cooked variety.
However, according to Lauren McGuckin, accredited practising dietitian and spokesperson for the Dietitians Association of Australia, it is not as black and white as it's made out to be.
“Raw or cooked, vegetables are still a nutritional powerhouse,” McGuckin told The Huffington Post Australia.
“However, during cooking, some nutrients will be lost."
The reason why raw vegetables can be the better option is due to the sensitive nature of some vitamins.
“Cooking does lead to a reduction in vegetables’ vitamin C, thiamin and folate levels. These vitamins are water soluble, therefore they dissolve in water,” McGuckin said. “However, this loss is modest and can be offset by eating a varied diet and quickly steaming or blanching vegetables instead."
Because of the sensitivity of some nutrients, eating raw broccoli has a higher nutritional value than cooked.
"Raw dark green veggies, for instance broccoli, is going to have a slightly higher iron value," McGuckin said.
While the cooking process can decrease the nutrient content of some vegetables, McGuckin said that other vegetables are actually more nutritious when lightly cooked.
What veggies to cook
“Besides enhancing flavour, cooking vegetables can enhance the nutrients and make them easier to digest -- potatoes, for example,” McGuckin told HuffPost Australia.
“Certain beneficial phytochemicals (natural plant chemicals) also become more available during cooking, therefore boosting the body’s ability to absorb them. For example, cooked tomatoes have a higher lycopene content than raw ones.”
Other vegetables which become more bioavailable include asparagus and carrots.
“Some of the phytochemicals in asparagus become more bioavailable with cooking,” McGuckin said.
“Spinach contains oxalates, which can inhibit the absorption of the iron within this iron-rich veggie. Cooking can help to reduce the oxalate content. Also, cooking carrots can improve their carotenoid bioavailability.
"It is the length of time that you cook your vegetables for that’s important.”
Revisiting childhood memories of brussel sprouts being boiled to oblivion? Well, boiling veggies not only makes them taste awful, it can also affect their nutritional content.
“Vegetables that are boiled in large amounts of water for a long time lose most of their nutrients because they leach into the water, which you then usually strain,” McGuckin said.
"On the flip side, quickly steaming or blanching your vegetables has been shown to retain the most nutrients out of all cooking methods."
What about soup? Has all our healthy pumpkin soup making been in vain?
“If you’re making a soup, generally everything is cooked in the one pot and the liquid component used to cook the veggies in is also consumed. There will still be plenty left in the vegetables themselves, as well as in the liquid surrounding them, so the loss is modest,” McGuckin said.
"You would lose a lot less nutrients roasting vegetables than boiling them away. It is a longer cooking method, but aside from what has leached out on the baking tray, which generally isn't much, the veggies are still going to retain a lot of nutrients," McGuckin.
From a food safety perspective, cooking vegetables helps reduce the risk of contamination.
“Heat also destroys harmful bacteria and micro-organisms, making vegetables safer to eat, which is particularly important for immunocompromised individuals or pregnant women, the elderly and young children,” McGuckin said.
Why Not Have Both?
"It doesn't mean one or the other is better -- there’s advantages for cooking certain veggies and for eating them raw," McGuckin told HuffPost Australia.
“A mix of raw salads and cooked vegetables is the best way to ensure you’re getting the most from these foods."
And, if you are cooking them, McGuckin advises to just not cook them too much.
"Essentially, don’t overcook vegetables as this will also destroy other vitamins and beneficial compounds. Just lightly them cook to retain as many of these nutrients, while enhancing others.”
Eat A Variety
According to McGuckin, the key to getting the most out of vegetables is eating a variety.
“Not all vegetables are equal,” McGuckin said.
“For example, green vegetables (particularly dark, green leafy ones) are an excellent source of folate, which is very important during pregnancy, as well as being high in iron. Red vegetables contain high levels of vitamin C, which helps ward off colds in the cooler months and assists in iron absorption. And orange and yellow veggies are full of vitamin A, which is great for eye health.
“Therefore, choosing different coloured vegetables means you’ll be getting a broader array of beneficial nutrients, phytochemicals and antioxidants.”
Just Eat Them
Whichever way you prefer to eat your veggies, the most important thing is to actually eat them.
“Just eat them! Research shows that only about eight percent of Australian adults meet the recommended daily intake of vegetables and fruit. Regardless of how these foods are cooked, the biggest priority is to get more people eating vegetables,” McGuckin said.