Eating when radiation is aimed near your digestive tract

This page is for people having radiation to the belly or pelvis, and the people cooking for them. It explains why diarrhoea happens, what to eat and drink, and when to call your team.

A radiation beam aimed at a tumour in the abdomen or pelvis has to travel through whatever else is in the way. NCI puts it directly. Radiation damages healthy tissue when directed at the abdomen, pelvis or rectum, and diarrhoea can follow.

Diarrhea is a known side effect of radiation to this area. It is not a sign the treatment is going wrong.

What you eat will not change the radiation, but it can change how rough the weeks feel.

NCI's management advice starts with drinking, not eating.

The suggestion is clear liquids such as water and broth, taken at room temperature. Room temperature is a small detail that people skip. It is easier on an irritated gut than something very cold or very hot.

Fluids lead the list for a reason. NCI describes severe diarrhoea as risking dehydration, and describes dehydration as life threatening. Keeping fluid going in is the part that matters most.

Two changes to how you eat appear in NCI's advice: smaller portions, and more often.

Small frequent meals put less through the system at once. On days when appetite is poor anyway, they are also simply more achievable than three full plates.

Low fibre is the other half of it. NCI lists low-fibre foods such as white bread, pasta and canned fruit.

Diarrhoea takes minerals out along with fluid. NCI suggests foods with sodium and potassium, such as peeled boiled potatoes, soup, bananas, applesauce and crackers.

Broth and soup are easy to keep in the cupboard during a course of radiation.

NCI lists foods and drinks that can make diarrhoea worse.

• Alcohol
• Milk and dairy products
• Spicy foods
• Caffeinated drinks
• Dried beans
• Foods high in fat
• Fruit juices
• Sugar-free gum or sweets

Dairy surprises some people. Ask your team when to bring foods back.

None of this is meant as a permanent way of eating. It is a temporary adjustment for a temporary problem.

NCI includes one piece of practical advice that has nothing to do with food: keep the anal area clean using warm water and baby wipes. A warm, shallow sitz bath can also soothe it.

Gentle cleaning is worth doing early. Tell your team if the skin breaks down.

Radiation courses run for weeks, and eating well through them affects how you tolerate the rest of treatment. Many cancer services have a dietitian. A referral is a reasonable thing to request rather than wait for.

Bring a few days of notes on what you have eaten and how your bowel responded. That turns a vague conversation into a specific one.

Dietary measures cover the milder end. NCI describes grades 1 and 2 diarrhoea as usually manageable at home. These grades mean up to six bowel movements above your normal daily number. NCI says grades 3 and 4 can be life threatening.

Report fever, dizziness, weight loss or blood in stools to your team, whatever your food intake looks like. NCI names all of those among the symptoms to report.

• Call your care team the same day if you are having seven or more bowel movements above your normal daily number. NCI puts that in grades 3 and 4, which it describes as possibly life threatening and sometimes needing hospital treatment.
• Call your care team the same day if you feel dizzy, run a fever, or see blood or mucus in your stools. NCI names all of these among the things to report.
• Call your care team within a day or two if you are losing weight, or if the diarrhoea is not settling on the food and fluid changes above. NCI asks people to tell the team about diarrhoea because dehydration can be life threatening.