Worst Foods for Your IBS - as part of the expert series by GeoBeats. Five foods that someone with IBS should avoid. Now, we still do not know the cause of IBS, but oftentimes food is the culprit. The first one is dairy products. Dairy products often end up being the main contributor to the symptoms in the condition. So, dairy products is number one. Alcohol sugars: Alcohol sugars actually break down in the colon, so they can cause a lot of gas and bloating diarrhea. They usually end in -ol, so if you are looking at an ingredient list, you can identify these easily. They are called menitol, or zorbitol, and those are the sweeteners that are usually found in low-carb foods, low-sugar foods. But, look for those and make sure you stay away from those. The gas producing foods, such as beans and broccoli. So, if you have IBS, try cutting these out. They do not affect everybody, but they affect enough people that it does make a difference. Caffeine: Caffeine is a stimulant to the gut, and it can make cramping and gas and things like that worse. So, try cutting out caffeine and see if that helps. And the last food is alcohol. Alcohol really irritates the lining of the stomach and the intestines and can make the problems worse.