Boiled broccoli with spices in a plate. Black background. Top view.


By Andrea Cannas


September 17, 2023


Should I keep boiling my greens?

Hands up if you’ve left your broccoli on the boil thinking it won’t make much of a difference anyway.

We often focus more on the health benefits of a food and less on how we cook it, for how long and what we pair it with. My undergraduate dissertation investigated the optimum cooking method that would best preserve or maximise the health promoting properties of broccoli.  Brassica vegetables, such as broccoli, contain plant chemicals called polyphenols that exhibit antioxidant and chemopreventive potential.

Cooking has shown to change the therapeutic properties of specific polyphenols depending on the method used, its intensity and the vegetable species. Methods that allow direct contact of the vegetable with cooking water can degrade the antioxidant profile by damaging the cell wall of the vegetable and causing the antioxidants to leach into the water.

The greener the cooking water is, the less antioxidant-rich your vegetable meal will be. 

Ranking from best to least protective:

  1. Sous-vide vacuum bag to 85°C, for 6 minutes
  2. Steaming for 2.5minutes
  3. Raw
  4. Microwaving in a bowl of water for no longer than 3 minutes
  5. Boil in boiling water for no longer than 2 minutes

Other things to consider with vegetable preparation:

  • Washing your vegetables with vinegar or a teaspoon of baking soda to remove pesticide residues.
  • Instead of using a knife, use your hands to ‘cut’ cruciferous vegetables into small florets/ pieces. Broccoli has a delicate structure and using a knife degrades the cell wall and polyphenol profile of the plant.
  • Eating broccoli or other cruciferous vegetables like kale, cauliflower or spinach with ground mustard seeds, radishes, rocket or wasabi can boost their benefits further.


*If you are boiling, submerge in cool water to stop the cooking process.

**If you boil your broccoli don’t chuck the water away! It is a great source of antioxidants that you can use to make a wholesome soup or thin and flavour a sauce with.


  1. Cartea ME, Francisco M, Soengas P and Velasco P. (2011) Phenolic Compounds in Brassica Vegetables. Molecules 16:251-280.
  2. dos Reis LCR, de Oliveira VR, Hagen MEK, Jablonski A, Flores SH, de Oliveira Rios A. (2015) Effect of cooking on the concentration of bioactive compounds in broccoli (Brassica oleraceavar. Avenger) and cauliflower (Brassica oleraceavar. Alphina F1) grown in an organic system. Food Chemistry 172:770-777.
  3. Martίnez-Hernández GB, Artés-Hernández F, Colares-Souza F, Gómez PA, Garcίa-Gómez P and Artés F. (2013) Innovative Cooking Techniques for Improving the Overall Quality of a Kailan-Hybrid Broccoli. Food and Bioprocess Technology6: 2135-2149.


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