I heard about this on a health show recently. I can't remember which show, but I've just googled it and found this: "... too much broccoli can cause hyperoxaluria, says Maurice A. Ramirez, DO, an emergency room physician and author of the soon-to-be-released book You Can Survive Anything, Anywhere, Every Time. "This is increased urinary excretion of oxalate caused by excessive intake of oxalate-containing foods (broccoli, cauliflower, cabbage, Brussels sprouts, etc.) resulting in kidney stones," says Ramirez.

And this:
Broccoli is one of the richest vegetable sources of calcium, iron, sulfur and magnesium. Furthermore, broccoli is contains abundnat pantothenic acid (Vitamin B5) and Vitamin A which may be very beneficial for wound healing and rough skin. Broccoli is a great source of Vitamin C, exceeding citrus.
It is important to note that broccoli has five goitrogenous chemicals which disrupt the body's ability to use iodine. It is important to limit or avoid in cases of thyroid deficency and low iodine.

It was really interesting what they were talking about on tv. If I remember, I'll let you know.