Cooking vegetables is usually a good idea: Heat breaks down cell walls, releasing antioxidants. But heating cruciferous vegetables (part of the Brassicae family) actually destroys their unique anti-carcinogenic potential. That’s because crucifers, unlike other types of vegetables, are high in glucosinolate, a plant compound that produces naturally occurring small molecules called isothiocyanates, which have been shown to fight cancer.
“An enzyme in cruciferous vegetables converts glucosinolates to isothiocyanates when they’re chopped or chewed,” says Canadian dietitian Leslie Beck, author of “The Complete A-Z Nutrition Encyclopedia: A Guide to Natural Health.” “But this enzyme is easily destroyed by heat. That means that heating cruciferous vegetables reduces the conversion of glucosinolates to their active isothiocyanates, which may reduce their cancer-fighting potential. You will preserve more phytochemicals in these vegetables if you steam them rather than boil or microwave.”
“Glucosinolate hydrolysis products could help prevent cancer by enhancing the elimination of carcinogens before they can damage DNA, or by altering cell-signaling pathways in ways that help prevent normal cells from being transformed into cancerous cells,” writes Dr. Jane Higdon, Nutrition Research Associate at the Linus Pauling Institute at Oregon State University. “Some glucosinolate hydrolysis products may alter the metabolism or activity of hormones like estrogen in ways that inhibit the development of hormone-sensitive cancers.”
It should be noted that people with goiter or hypothyroidism must limit their intake of cruciferous vegetables, which are goitrogenic; i.e., they induce the formation of goiter through enzymes that interfere with iodine uptake. And as with most things, too much glucosinolate can be hazardous, particularly for people who are seriously ill. Always check with your doctor about any dietary changes. But for people who have no problem eating crucifers, these unique vegetables should be a part of a healthy diet, especially considering the fact that there is a growing body evidence that they are effective at protecting against cancer. MORE