Colon cancer diet: Navigating nutritional challenges during treatment

Colon cancer diet
Colon cancer and its treatment affects your body's ability to digest and absorb nutrients. This article explains what to eat when you have colon cancer.


Nutrition is important for all cancer patients, but nutrition isn’t only about consuming healthy foods and beverages: Your body needs to actually absorb nutrients in order to benefit from them.

The main function of the colon is to absorb electrolytes and fluid, but colorectal cancers and their treatments may impede nutrient absorption. Treatment for colon cancer patients may include having part of the colon surgically removed, leaving patients with needs that are different from those of patients with other types of cancer.

Side effects of chemotherapy treatment may include nausea, vomiting, loss of appetite, diarrhea or constipation—any of which presents nutritional challenges during treatment.

While many cancer patients are at risk of malnutrition and dehydration, those with gastrointestinal cancers (which includes colorectal cancer) are even more likely to experience some degree of malnutrition, which may affect a patient’s ability to complete treatment.

Getting proper nutrition during treatment helps patients maintain a healthy weight, muscle mass and energy levels—all of which contribute to the ability to tolerate cancer treatment and to prepare for survivorship.

Specific nutritional needs during treatment for colon cancer vary according to every patient’s situation. Patients with pre-existing conditions like heart disease or obesity face different challenges than those who begin treatment in relatively good health. Patients’ needs also vary according to where they are in the treatment process and the side effects they experience.

In general, colon cancer patients need to stay hydrated and eat healthy foods that are high in proteins, vitamins, antioxidants and electrolytes to help them achieve adequate caloric needs. Working with a professional dietitian who can help you meet those needs, and who can monitor your nutritional status over the course of your treatment regimen, may help reduce your chances of experiencing nutritional deficiencies during treatment.

To help you navigate your diet during colon cancer treatment, this article covers:

If you’d like to learn more about nutritional support during colon cancer treatment or our integrative approach to cancer care at City of Hope, call us or chat online with a member of our team.

Diet for colon cancer patients: General guidelines

The nutritional guidelines for colon cancer patients are similar to those intended to promote cancer prevention and wellness in the general population.

The American Cancer Society recommends a variety of foods and nutrients during treatment, including healthy sources of proteins, carbohydrates, fats, vitamins and minerals, to help your body respond to the challenges of cancer treatment.

The following guidelines are general recommendations. Your unique circumstances, risk factors, treatment method and the side effects you experience determine your specific dietary needs. Ask your health care providers for their medical advice for your personal circumstances.

Maintaining a healthy weight during colon cancer treatment

Maintaining a healthy weight through proper nutrition during cancer treatment is a challenge for many patients, but the benefits are numerous. It may boost your immune system and help provide the energy you need to stay active. Even small amounts of weight loss may increase your risk of experiencing treatment-related side effects. And extreme weight loss during treatment may result in hospitalization or the need to pause or delay your treatment.

On the other hand, obesity may negatively impact treatment and increases the risk of death in some cancer patients. Obese patients are also at a higher risk of colorectal cancer recurrence compared with patients who are at a healthy weight.

Your doctor or a registered dietitian can calculate your daily recommended calorie requirements, but generally, we advise 25-30 calories per 2.2 pounds of body weight per day, with no more than 25 percent of calories coming from fats.

Nutrients to include in your colon cancer diet

Colon cancer diet

Electrolytes, like potassium, magnesium, sodium and calcium, are essential minerals that help your body maintain the appropriate balance of fluids. Good sources of electrolytes are green leafy vegetables like lettuce and kale; fruits like watermelon, bananas and avocados; and potatoes, beans, almonds and peanuts. It’s important for colon cancer patients to monitor their intake because colon cancer and its treatment may interfere with electrolyte absorption. Losing fluids from diarrhea, vomiting or sweating may also contribute to electrolyte imbalance.

Proteins help the immune system fight infection and help the body repair tissues after surgery, chemotherapy or radiation. The exact amount needed differs from patient to patient. We typically recommend .04-.05 ounces of protein per 2.2 pounds of body weight every day for a healthy person who's not very active.

The source of protein is just as important as the amount. Avoid red meat and processed meats like hot dogs. Choose lean proteins like eggs, fish and poultry instead. Good plant-based sources of protein are lentils, nuts and legumes.

Roughage, or fiber, is the fibrous, indigestible material part of plant-based foods that aid the passage of food through the intestines. Whole-grain flour, brown rice, fruit, vegetables, nuts, seeds and legumes like lentils and black beans are all good sources of dietary fiber.

Carbohydrates provide much-needed energy for the body and the brain. They are also good sources of roughage, vitamins and minerals.

Misconceptions surrounding some popular low-carb diets have led some people to equate all carbohydrates with unhealthy sugars. While sugars are a form of carbohydrate, not all sources of sugar (and carbohydrates) are equal.  

You should seek out complex carbohydrates, which are found in whole foods like beans, oatmeal, whole-wheat bread, barley and whole fruits. Some carbohydrates, such as beetroot and sweet potatoes, have the added advantage of being good sources of antioxidants. Complex carbohydrates help the body maintain muscle mass and regulate blood sugar, and they’re healthy sources of fiber and nutrients.

Limit or avoid simple carbohydrates that are found in foods like refined flours, table sugar and syrup. While there’s no conclusive evidence that sugar feeds cancer, we generally recommend limiting intake of sugary foods and drinks. Excess sugar may lead to unhealthy weight gain and high blood-sugar levels. Foods containing added sugar also tend to be low in nutritional value.

Healthy fats give the body energy and reduce inflammation, and they may help the brain and nervous system function properly. Healthy fats are found in foods like fish, seeds, nuts, avocados and olive oil. We recommend these sources rather than red meats, fast food and dairy products like cheese and butter. We generally recommend that no more than 25 percent of your calories come from healthy fats.

Vitamins are also a key part of the colorectal cancer journey. Low levels of vitamin D have been associated with poor outcomes in some cases and may negatively impact survival. When patients are deficient, we recommend supplements. Other important vitamins are B complex, vitamin A and vitamin C, each of which plays a crucial role in the body’s ability to recover from, and tolerate, colorectal cancer treatment.

Adequate hydration is crucial during and after treatment. Dehydration can cause a range of problems from headaches, constipation and fatigue to low blood pressure and even life-threatening shock. Staying hydrated may also reduce treatment-related side effects.

For a generally healthy cancer patient, we typically recommend eight glasses of water or low-sugar electrolyte drinks per day. If you’re losing fluids due to a colostomy, diarrhea or even sweating outside on a hot day, you’ll need to drink more fluids to compensate.

An easy way to be sure you’re well-hydrated is to pay attention to your urine output: If you’re urinating less than usual, for instance, or if your urine has a strong color or odor, you’re likely not getting enough fluids. Other signs of dehydration include fatigue, dizziness and constipation.

What to eat during colon cancer treatment

The majority of colon cancer patients undergo surgery, followed by four to six months of chemotherapy. Those with stage 4 colon cancer may be treated with chemotherapy only, and those with rectal cancer may undergo chemotherapy and radiation therapy followed by surgery. Each of these treatment types may present different nutritional challenges.

While most patients should strive to follow the general recommendations for good nutrition, there are times when it’s difficult or not recommended. Side effects like nausea, diarrhea or loss of appetite are common in certain stages of treatment and may require dietary modifications. Your general health also affects your specific needs.

Diet before and after colon cancer surgery

Protocols for diet before and after colon cancer surgery have changed over the years. Previously, patients fasted for 12 hours before surgery, and food was withheld for a period of time afterwards.

At City of Hope, we follow the ERAS (Enhanced Recovery After Surgery) treatment program protocols, which have been shown to reduce surgery complication rates and shorten post-surgery hospital stays

Part of the ERAS protocol involves ensuring that patients are as well nourished as possible before their surgery. Studies have shown that patients who are well-nourished before surgery tend to have better outcomes, including reduced hospital stays and fewer complications, than those who are malnourished. In severely malnourished patients who can’t get adequate nutrients by mouth, intravenous nutrition for a few weeks before surgery may improve their outcomes.  

About a week before surgery, we put our patients on a drink that’s high in omega-3 fatty acids and micronutrients to reduce the chances of complications. Immediately before surgery, we give patients a carbohydrate drink to help stabilize their blood sugar levels during the procedure.

Our patients generally start taking clear liquids within 24 hours after surgery and then advance to solid foods within two to three days. We try to avoid too much roughage initially, but within a week, most of our surgical patients can return to a normal, healthy diet.

Avoiding use of narcotic pain medication after surgery is another key step in reducing hospital stays and returning to normal digestive tract function. We prefer to use non-narcotic pain medications like ibuprofen instead.

Diet during chemotherapy for colon cancer

Several common side effects of chemotherapy may affect your ability to eat and digest food. These may include:

Some chemotherapy drugs used to treat colon cancer are known to cause severe diarrhea in some patients. We generally advise patients on that drug to stay away from high-fiber foods such as green vegetables, raw fruits, raw veggies and whole grains. These patients may do better on a diet of pasta, white rice and healthy sources of low-fiber protein.

Patients who’ve lost their sense of taste or who are nauseous may need a high-calorie diet of bland foods, such as eggs, fish, turkey and chicken.

The Cancer Support Community provides a free resource with suggestions on how to cope with specific eating-related side effects of cancer treatment.

Hydration is important, too, especially if you’re losing fluids due to diarrhea and vomiting, so be sure to take in plenty of fluids as outlined above or as recommended by your doctor.

If you’re experiencing any of these side effects, talk to your care team about your concerns. Anti-nausea and anti-diarrheal medicines may be helpful. Also, ask if supportive care services are available to help you manage treatment-related side effects.

Diet during radiation for colorectal cancer

Radiation therapy is used in patients with rectal cancer. This therapy tends to cause its own unique side effects, which may include irritation of the rectum and diarrhea. We generally recommend that these patients follow a low-roughage diet to reduce irritation. Patients who aren’t experiencing adverse effects can usually follow a regular diet soon after treatment.

The importance of one-on-one nutritional guidance during cancer treatment

Colon cancer diet

No matter your treatment regimen, it’s important that someone from your care team monitor your weight and nutritional status throughout treatment and is available to answer your questions. You should report any weight loss, unexplained dizziness, vomiting or other conditions that affect your ability to eat and keep food down.

If possible, work with a registered dietitian who can help you with your specific dietary needs throughout treatment. A dietitian can help calculate your caloric requirements and design appropriate meal plans for you. Dietitians with oncology experience may prepare you in advance of treatments and detect issues before they have a chance to become more serious problems.

Our care team is familiar with common side effects of cancer and its treatment and their impact on appetite and nutrition. We proactively monitor our patients for malnutrition and nutrition-related problems. We anticipate common treatment-related side effects and help prepare patients for them, so we can help them prevent and manage their side effects.

We offer our patients one-on-one consultations with registered dietitians, some of whom are board-certified specialists in oncology nutrition (CSO). 

Our dietitians evaluate patients’ nutritional status and design custom meal plans for them. They even developed a recipe book especially for cancer patients.

These nutritional services are only one facet of our integrative care approach to cancer treatment. We also offer naturopathic support, which includes guidance on dietary  supplements and homeopathic remedies. Licensed mental health professionals in our behavioral health program help patients whose mental state is affecting their appetite and ability to eat.

Good nutrition is a vitally important component of fighting cancer. Making healthy food choices early in the course of treatment may help improve your quality of life during treatment with the added benefit of helping you establish healthy long-term nutritional habits for your future.

If you’d like to learn more about how we treat colorectal cancer and our integrative approach to cancer care at City of Hope, call us or chat online with a member of our team.