American Researchers Found That Steaming Broccoli
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Cruciferous vegetables such as collard greens, kale, watercress, Brussels sprouts, and broccoli are widely celebrated from their anti-cancer effects. [1] According to a study published in the Journal of Agricultural and Food Chemistry, the mode of preparation affects the nutritional content of broccoli – and in particular, the sulforaphane yield. [2]
Sulforaphane is an active compound found in cruciferous vegetables that is formed when inactive glucoraphanin interacts with the enzyme myrosinase. It’s has been shown that sulforaphane has potent anticancer properties against prostate cancer cells, breast cancer, and colorectal cancer. [3][4][5]
According to the study, steaming broccoli for a few minutes increases the sulforaphane content by eliminating an inhibitory heat-sensitive protein known as the epithiospecifier protein, but retaining myrosinase. (Ps: The epithiospecifier protein inactivates sulforaphane, while myrosinase facilitates the activation of glucoraphanin into sulforaphane).
Boiling broccoli for more than a minute is believed to destroy most of the myrosinase – hence reducing the cancer-fighting abilities of broccoli. Additionally, some water-soluble nutrients such as folate, B-vitamins, and vitamin C may leach into the boiling water – reducing the nutrient content of the broccoli.
Please note that this content should never be used as a substitute for direct medical advice from your doctor or other qualified clinicians.
[1] Cruciferous Vegetables and Cancer Prevention https://www.cancer.gov/about-cancer/causes-prevention/risk/diet/cruciferous-vegetables-fact-sheet.
[2] Impact of Thermal Processing on Sulforaphane Yield from Broccoli (Brassica oleracea L. ssp. italica) https://pubs.acs.org/doi/abs/10.1021/jf2050284.
[3] Singh AV. et al. 2004. Sulforaphane induces caspase-mediated apoptosis in cultured PC-3 human prostate cancer cells and retards growth of PC-3 xenografts in vivo. https://www.ncbi.nlm.nih.gov/pubmed/14514658/.
[4] Li Y. et al. 2010. Sulforaphane, a dietary component of broccoli/broccoli sprouts, inhibits breast cancer stem cells. https://www.ncbi.nlm.nih.gov/pubmed/20388854.
[5] Wu QJ. et al. 2013. Cruciferous vegetables intake and the risk of colorectal cancer: a meta-analysis of observational studies. https://www.ncbi.nlm.nih.gov/pubmed/23211939.