This is an important question to discuss with your gastrointestinal physician. Foods usually do not cause blood in the stool. It is possible that you may be allergic to certain types of foods. If you are allergic to it, it may explain some of the cramps and blood that is coming from your rectum. There are also certain products that people drink/eat that can cause gastritis such as alcohol, coffee, certain medications. Gastritis can lead to ulcers that bleed in the stomach. Moreover, you mention that you have bright red blood from the rectum which suggest lower gastrointestinal bleeding
though it does not rule out upper gastrointestinal bleeding. Some common causes of lower GI bleeding are diverticulosis, diverticulitis
, and hemorrhoids
. Diverticulosis is painless and has bright red blood. Diverticulitis can be painful and may be located in the right lower quadrant of your abdomen. Hemorrhoids can either be internal or external. Internal hemorrhoids do not hurt but they do bleed; on the other hand, external hemorrhoids are painful and may bleed. The bright red blood is concerning and should be investigated further. Other possibilities include infection by bacteria. You should make an appointment with a gastrointestinal physician. They may run tests on your stool. They may also consider doing something called a colonoscopy to look inside. If you continue to have significant bleeding, you should go to the emergency room.