You might have heard the anti-boiling brigade claiming this cooking method can ‘kill’ the nutrients, but let’s bust the boiling myth!
Yes, the way your vegetables are cooked can change their nutritional profile a little, but that doesn’t mean boiling is ‘bad’, or that there’s a ‘best’ or ‘worst’ way of prepping your meals. As with everything in nutrition, it’s just not that clear cut.
Let me explain…
The key factors that can impact the nutrients in vegetables when you’re cooking are:
- Water: how much liquid is used
- Heat: how hot they’re cooked
- Time: how long they’re cooked for
While boiling can reduce certain nutrient levels, it can make other nutrients more accessible.
On the plus side
Heating vegetables can increase the availability of some nutrients, making them easier to absorb, get into our bloodstream and feed the rest of our body.
Boiling carrots, for example, has been shown to increase levels of beta-carotene absorbed (the plant chemical responsible for the orange glow).
This is because beta-carotene isn’t heat sensitive (unlike vitamin C). In fact, the heat can help soften the plant walls where the beta-carotene is trapped, making it more accessible.
In turn, beta-carotene is transformed into vitamin A in our body to support immunity and eye health.
Boiling tomatoes has also been shown to increase the lycopene levels too.
On the other hand…
Water-soluble vitamins (i.e. dissolvable in water), such as vitamin C and the B vitamins, can often reduce during boiling as they ‘dissolve’ into the water (ever seen the water changing colour when you boil veggies like broccoli or sweet potato?). So, boiling in heaps of water can lead to some loss of water soluble vitamins.
One study looking at the effects of boiling on different veggies found boiling spinach and broccoli could reduce the vitamin C content by 50% or more, and boiling courgette / zucchini and sweet potato reduced the vitamin C by about a third.
BUT It’s important to remember that most of us easily hit our daily intake of vitamin C through diet anyway. Plus, you’ll still be getting the gut-loving fibre and plenty of other nutritious goodness, so there’s no need to avoid boiling all together, especially if it’s your favourite way to cook veggies.
Top tips for boiling
- Try to use less water where possible – enough to just cover the vegetables
- Keep the skins on your vegetables for extra nutrients and fibre
- Keep an eye on the time – boil your vegetables long enough to enjoy eating them, but try to keep that delicious crunch (no one likes an over-boiled soggy sprout!)
- Make use of the liquid too. One for the soup-lovers: enjoying the liquid and blending up into a soup captures these water-soluble nutrients and all the amazing flavours
The bottom line
Ultimately, if you’re having plenty of plant-based foods, including different forms of cooked vegetables, you’re still going to get plenty of vitamins even if you lose a little bit here and there.
So enjoy your veggies however you like them – the most important thing for your gut, and overall, health is to get as much variety of all of your plant-based foods as you can.
It’s worth mixing it up and enjoying different food forms – if you boil your vegetables one night, why not try drizzling on some extra virgin olive oil and roasting them next time.