I read somewhere that there is something in brocolli and cabbage that makes it dangerous to eat it raw because it will cause bulging of the bottom of the throat.
Does that leach into the water when boiling and therefore would it be unhealthy to drink the water used to boil brocolli and cabbage?
"We conclude that cruciferous plants are safe in humans, with the exception of allergies."
I would avoid the water if I had an allergy to them.
Allergies can get better and go away completely the more clean and less toxic our bodies become.
You can self test for food allergies at home by avoiding the food for a week- then eat it on an empty stomach, away from other foods. Then see how you feel for twenty four hours. You can find other methods too.
You may be referring to cruciferous vegetables containing "Goitrogens" which can give you a goiter. This can only happen if you eat very large amounts (and juicing is more potent).
I've never heard a warning about the water, or that raw makes a difference. Your source sounds like a quack. And I don't wanna add to the bro-science, but my brother (yep) eats a lot of cabbage. He doesn't have a throat issue. But he does have other issues. I do recommend limiting cruciferous vegetables.