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Didn't your mother say, "Eat your broccoli"?
The cruciferous vegetables like broccoli, brussels sprouts, cabbage, bok choy, and cauliflower (Brassicas) are good for us under some circumstances. It just so happens I like them, especially broccoli. Yum!
The "good for us" part is that they contain a substance called I3C; when they are chewed, swallowed, and get to the stomach acid, I3C's combine to form another substance (DIM) that causes the liver to block some toxic enzymes, and helps protect the body against environmental estrogens. (Technical information here.) Most of our foods come to us carrying residues of herbicides, pesticides and even residues from plastic packaging; these substances all have estrogen-like endocrine disruptors.
It is suggested to eat these cruciferous vegetables every day (and eat lots of them) to fight disease, especially cancer. That's the good news.
The bad news is that cooking deactivates the good-healthy-for-us I3C. Additionally, cruciferous vegetables contain goitrogens which inhibit thyroid function, and for someone like me with a low thyroid condition, it's a big problem. (Your thyroid controls how quickly the body uses energy, and how it makes proteins.) So that means cooking brassicas isn't good for anyone because it deactivates I3C. Eating them raw is fine if your digestive system can handle it. (I love raw broccoli on a crudities tray but it always gives me terrible indigestion.)
So the answer is to learn to make and eat your cruciferous vegetables fermented, because culturing maintains the I3C which would be lost by cooking, and culturing neutralizes the thyroid-depressing substances. By cultured, I mean more than just pickles and sauerkraut. Fermented cauliflower and carrots would be a nice topping on a garden salad, and I love a few pickled onions on a sandwich. I have Sandor Katz' book on wild fermentation, but a quick glimpse on Amazon lists several books that contain basic fermenting techniques and recipes.
When I was a young adult, my boyfriend and I frequented a few Jewish Deli's over on Miami Beach. On every table, right along with the ubiquitous salt and pepper, was always a relish tray with small bowls of sauerkraut, and other pickled (fermented) vegetables. Howie said it was for good digestion.
I never thought about it much back then, but now it makes perfect sense to me. Cultured Raw Vegetables contain high amounts of probiotics, and ingesting just a little bit of all those natural enzymes aids our digestion and begins to re-colonize our intestinal tract with the good guys.
Just FYI: Canola oil is made from rapeseed, which is a Brassica.