As a vegetarian my consumption of grains was quite excessive, I did not notice for a while and thought 'grains" were healthy.
Recently I did a 10 day elimination of grains all grains including corn and potatoes and deep fibromyalgia type pain has gone. I do not have the time to elucidate on the benefits. My life is vastly improved. My diet is simple only veggies, low glycemic fruit, fat and dhal. I eat very little carbohyrdrate and even stay away from starchy or over sugared root vegetables as they cause insulin spikes.
Elimination Diets and all the guess work take a lot of time and effort and guesswork. I have tried them for years to determine my sensitivities and always end up going back to the offending substances because I am never sure.
Grains are not needed for help. I would cut the middle man dump all grains and heal what is being referred to as IBS. When the organism is healthy then if you like add back what you consider to be healthy grains (if any) Read mercola concerning grains and starches.