bad bowels

my friend has had food poisoning 3 times in the last 3 months. She recently has had diarrhea and cramping is now on medication advised not to eat caffeine, vegetables, and only boiled meat and starches. She has lost a lot of weight. THe doctor said after testing that it is not a parasite. what could it be? can you point me in the right direction to a site where she or I can list symptoms and see if an ailment matches? Tweet