Are you sure you aren’t thinking of nightshade(tomato, pepper, eggplant, etc)? I’ve never heard of the mustard family(cabbage, cauliflower, broccoli) having any harmful side effects.
http://www.sciencedaily.com/releases/2011/04/110419101234.htm
“Our research shows that peppermint acts through a specific anti-pain channel called TRPM8 to reduce pain sensing fibres, particularly those activated by mustard and chili. This is potentially the first step in determining a new type of mainstream clinical treatment for Irritable Bowel Syndrome (IBS).”