Foods to Eat During Prostate Radiation Therapy: Practical Diet Guide

Hello Lois,

Your husband’s bowel and urinary symptoms after several sessions of external beam radiation therapy for prostate cancer are not unusual. Radiation aimed at the prostate can irritate the nearby rectum and bladder.

The important point is that the diet should be adjusted to what he is experiencing now. A healthy high-fiber diet may be appropriate when someone has no bowel symptoms, but the same foods can aggravate diarrhea, cramping and gas during pelvic radiation.

First: Tell His Radiation Team About the Symptoms

Please tell his radiation oncologist, radiation therapist or oncology nurse about both the bowel and urinary problems.

Pelvic radiation can cause bowel symptoms such as:

• loose stools or diarrhea;
• abdominal cramping;
• gas and bloating;
• urgency to have a bowel movement;
• rectal irritation; and
• occasionally mucus or blood.

It can also irritate the bladder and urinary tract, causing:

• more frequent urination;
• urinary urgency;
• burning when urinating;
• difficulty starting the urine stream; or
• a weaker stream.

What Foods Are Usually Easier on the Bowel?

If your husband has diarrhea, cramping or frequent bowel movements, foods that are relatively low in insoluble fiber and easy to digest are often better tolerated temporarily.

A Simple One-Day Meal Example

This is only an example. The aim is not to restrict his diet more than necessary, but to identify foods that reduce symptoms while still providing enough calories and protein.

Foods That May Make Diarrhea or Gas Worse

When bowel symptoms are active, some people do better temporarily limiting:

• bran cereals and large amounts of whole grains;
• large raw salads;
• fruit and vegetable skins;
• beans, lentils and chickpeas if they produce gas;
• cabbage, broccoli, cauliflower and onions if they increase bloating;
• fried or very fatty meals;
• very spicy food;
• large amounts of caffeine;
• alcohol;
• carbonated drinks; and
• artificial sweeteners such as sorbitol if they worsen diarrhea.

Not everyone reacts to the same foods. A simple food-and-symptom diary can help identify his individual triggers.

Does He Need a High-Carbohydrate Diet?

No special high-carbohydrate diet is required simply because he is receiving radiation.

Carbohydrates can certainly provide useful calories, particularly when appetite is poor, but the goal is an adequate overall intake of protein, energy, fluids, vitamins and minerals from food, and foods that he can comfortably tolerate.

The old explanation that radiation damages enzymes and therefore requires “a lot of carbohydrates” is not an evidence-based reason to prescribe a high-carbohydrate diet.

Protein Is Still Important

Protein helps maintain muscle and nutritional status during cancer treatment. Useful choices include eggs, chicken or turkey, fish, lean meat, yogurt or cottage cheese if tolerated, tofu, and smooth nut butter in modest amounts if it does not worsen symptoms.

If appetite is reduced, smaller meals every few hours may be easier than three large meals.

Should He Take Vitamin or Antioxidant Pills?

Do not automatically start high-dose vitamin or antioxidant supplements during radiation therapy.

Major cancer centers recommend telling the oncology team about every supplement being used. Some oncology programs advise avoiding high-dose antioxidant supplements during radiation unless they have been specifically recommended for a documented deficiency.

How Much Should He Drink?

Hydration is important, particularly if he is having diarrhea.

Many pelvic-radiation programs advise roughly 2 to 3 liters of fluid per day when medically appropriate, but your husband’s own treatment team’s instructions should take priority because heart disease, kidney disease and other conditions can change fluid requirements.

Also follow the radiation center’s instructions about having a comfortably full bladder before each treatment. Many prostate-radiation plans use a specific bladder-filling routine to help keep the bladder and small bowel positioned consistently.

What Drinks May Irritate the Bladder?

If urinary urgency or burning is troublesome, it may help to reduce coffee, strong tea, cola, energy drinks, alcohol and other drinks that clearly aggravate his symptoms.

Do not drastically reduce fluid intake just to urinate less frequently unless his medical team specifically tells him to do so.

What If Dairy Makes the Stomach Problems Worse?

Some people temporarily become more sensitive to lactose during pelvic radiation.

If milk causes bloating, cramping or diarrhea, try lactose-free milk or reduce ordinary dairy temporarily. Yogurt may sometimes be better tolerated.

There is no reason to eliminate dairy automatically if it is not causing symptoms.

What If He Is Constipated Instead of Having Diarrhea?

This is important because not everyone receiving prostate radiation develops diarrhea. Some people become constipated because of medication, changes in diet, lower activity or other factors.

If constipation is the problem, a low-fiber diet may actually make it worse. His radiation team should therefore know his exact bowel pattern before recommending dietary restriction.

When Should You Call the Treatment Team Promptly?

Will the Urinary and Bowel Symptoms Always Disappear After Radiation?

Most acute bowel and bladder symptoms improve after treatment ends, but it is too definite to promise that they will disappear within one or two weeks.

For many patients, improvement occurs gradually over several weeks. A minority can develop persistent or delayed bowel or urinary effects months or years later.

That is another reason to keep the radiation team informed rather than simply waiting for symptoms to resolve.

Emotional Support Matters Too

Your support is valuable, but your husband should not feel that he has to remain positive all the time for treatment to work.

Cancer treatment can cause anxiety, fatigue and emotional strain. Practical support—helping with meals, transportation, appointments and communicating symptoms to the treatment team—can be just as important as encouragement.