I have mentioned this before but here's some more info. A very nice doctor who ended up not helping me on IBS, did research himself to try to help with gas problems and gave me a medical article. He said not much research on it but this helped me immensely. I will mention some parts in hopes of helping others but the cite is "Contemporary Internal Medicine", January 1991, pages 29-41. Maybe someone more sophisticated than me can find it online for others to read but I caution that it's written for doctors: if I just list it can cause--fructose, sorbital used in low cal foods causes copious hydrogen production; complex carbohydrates corn, oats, potatoes, wheat-rice is the only commonly used that unlike those is almost completely absorbed (and therefore does not cause); fiber has general structure like carbohydrates above and increased hydrogen excretion almost always associated with its ingestion (metamucil did it to me and citrucel is better for me); controlled trials of simethicone not very convincing; one study suggested that elimination of aqueous milk products and wheat helped in functional abdominal pain; avoid large amounts of complex carbohydrates, legumes and aqueous milk if lactose intolerance is suspected is impt.; high concentrations of lactose in cottage cheese, ice cream and milk but not cheeses from milk; avoid sorbital and soft drinks high in fructose; "many patients find such restrictive diet intolerable and prefer to suffer from flatulence."----hope I don't know any of them. The end of that. I found that wheat definitely does it to me and that I'm lactose intolerant so milk does. I eat a lot of brown rice with some wild rice mixed in (it is a grass not a rice for those who may have grass problems)both are very good for you, I got an automatic rice cooker; and I use rice milk not regular milk for cereal mostly brown rice cereals with some oats thrown in.