Colorectal cancer is the third most common cancer diagnosed in both men and women in the U.S., excluding skin cancers. While overall rates of people being diagnosed with colorectal cancer have decreased each year, young people are developing colorectal cancer at higher rates than ever before. Because of this uptick, the American Cancer Society lowered the recommended screening age in 2021 from 50 to 45 years old.
Nutrition plays a critical role in prevention and treatment. The foods you consume and the lifestyle you lead impact your cancer risk levels and your body's ability to prevent cancer. Some cancer research studies have found that people who eat right, get regular physical activity, maintain a healthy weight and limit alcohol consumption can cut their odds of colorectal disease by more than a third.
Learn what foods to choose or lose to achieve a balanced diet for colorectal cancer prevention, plus dietary guidelines to follow during treatment.
What is colorectal cancer?
Colorectal cancer starts in the colon or the rectum and is referred to as either colon cancer or rectal cancer depending on where it starts. These cancers are often grouped together because they share many similar features.
Both the colon and rectum play an essential role in your digestive system by processing waste through your body. When abnormal cells develop along the lining of your large intestine or rectum, this is referred to as colorectal cancer.
Risk factors
Overall, the lifetime risk of developing colorectal cancer is about one in 23 for men and one in 26 for women. However, each person's risk might be higher or lower depending on their risk factors. These may include:
- Being overweight or obese
- Low physical activity
- Diet
- Smoking
- Alcohol use
- Age
- Personal or family history of colorectal polyps or colorectal cancer
- Pre-existing conditions
- Racial or ethnic background
The American Cancer Society recommends that individuals at average risk begin regular screening at 45 years old.
Daily dietary choices for colorectal cancer prevention
The food and drinks you consume can be powerful tools for colorectal cancer prevention. A nutritious regular diet can improve your gut health, which is a main contributor to colon and rectal health.
Think of food as medicine—when you're mindful about the products you're consuming, you can arm your body with the nutrients it needs to prevent or fight off cancer cells.
Healthy practices to reduce risks and prevent colorectal cancer
Smart food choices can reduce the risk of colorectal cancer. In general, the American Cancer Society recommends that adults and children choose diets rich in high-fiber foods, such as whole fruits, veggies and whole grains. Practices for prevention include:
- Increasing your dietary fiber intake. Consume fiber-rich foods, such as whole wheat bread or brown rice, and beans and legumes, such as soybeans, lentils, peas, pinto beans, black beans and kidney beans. These are great sources of protein, fiber, vitamin B and vitamin E. According to the American Institute for Cancer Research, "Dietary legume consumption reduces the risk of colorectal cancer."
- Maintaining a nutritious diet. Eat a variety of plant-based foods. Make healthy food choices, like vegetables, whole grains, legumes (beans) and nuts. Consume lean protein in moderation, like fish and poultry, and choose low-fat dairy products when possible.
- Drinking plenty of water. Stay hydrated—ensure you're getting enough fluids each day. The majority should come from non-caffeinated beverages.
- Eating more dairy. According to the American Institute for Cancer Research, there is strong evidence that the consumption of dairy can be protective against colorectal cancer.
What to avoid
Certain food and drink—especially in high quantities—can cause an increased risk of colorectal cancer. To lower your risk:
- Avoid alcohol. Alcohol increases your risk of developing cancerous cells. It turns into cancer-causing compounds in the body, which can also damage the cell lining of the colon.
- Rethink your go-to fast food order. Traditionally, fast food is highly processed, low in nutrients and may contribute to obesity which increases cancer risk. If you’re in a pinch and need to grab lunch on the go, try a restaurant that uses fresh ingredients and offers fruit, vegetables or whole grains as a side dish.
- Limit products with high glycemic loads. Foods such as white rice, noodles, cake and sugar have a lot of refined carbohydrates and sugars. You don’t have to forego these goods altogether but try to limit consumption, as cancer research has found a clear and direct link between foods with a high glycemic load and colorectal cancer. These trigger a greater tendency toward insulin resistance.
- Eat less red meat and processed meats. Processed meats and red meats, such as deli meat or hot dogs, may be associated with an increased risk of developing colon cancer. This is due to the presence of compounds such as heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs), which are created when red meat is cooked at high temperatures. Additionally, compounds in red meat known as advanced glycation end products (AGEs) have been linked with inflammation in the body, which can also lead to increased colorectal cancer risk.
Quick dietary guide: Top foods to choose or lose
Stacy Shawhan, registered dietitian and certified specialist in oncology nutrition at the University of Cincinnati Cancer Center, knows how powerful diet can be in fighting illness or treating cancer. She's an expert at crafting nutritional plans to support individuals throughout their health or cancer journey.
Here's what Stacy recommends to prevent colorectal cancer:
What to choose:
- Whole grains. Brown rice, oats, 100% whole wheat bread products, quinoa, faro, barley and whole grain pasta.
- Dairy products. Low-fat milk, yogurt, cottage cheese and other cheese products. Cancer research suggests the high calcium content in these may be protective.
- Non-starchy vegetables and raw fruits. These are high in fiber, which promotes gut health. These also contain phytonutrients known to prevent many types of cancer.
What to lose:
- Alcohol. If you do drink alcohol, try to do so only occasionally and limit to two standard drinks per day for men or one standard drink per day for women
- Red and processed meats. Processed meat is any meat (white or dark) that has been preserved through salting, smoking or curing (such as salami, sausage, bologna, lunch meats and hot dogs). Both red meat and processed meat contain compounds that increase the risk of colon cancer.
Stacy's Top 5 healthy foods to prevent colon cancer:
- Oatmeal
- Yogurt
- Citrus fruit
- Bell peppers
- Fish
Nutrition for colorectal cancer patients in treatment
When a patient develops colon or rectal cancer, the most common treatments include:
- Surgery
- Chemotherapy
- Radiation
- Participation in clinical trials
Each treatment type may present different nutritional challenges, which a specialized diet can support.
General dietary guidelines for colorectal cancer patients
At the University of Cincinnati Cancer Center, we have specialized, oncology-trained dieticians who work with patients—no matter where they are in their health journey—to build personalized nutrition plans. These plans consider each individual's primary cancer treatments and medical history to promote overall wellness, outcomes, and patient comfort.
Stacy Shawhan, one of the University of Cincinnati Cancer Center’s certified specialists in oncology nutrition, shares nutritional guidance for patients in treatment.
Nutritional guidelines for cancer treatment
As you move from diagnosis through surgery and other treatments, your dietary needs will change. You should always follow your provider’s advice when undergoing treatment for cancer. However, certain practices, like changing your diet, can improve your overall health and help reduce treatment-related side effects. Stacy recommends that you:
- Get adequate calories. Eating enough to maintain your weight and muscle mass during colorectal cancer treatment can improve patient outcomes while helping patients better tolerate treatment. Many people need more caloric energy after diagnosis than they do before diagnosis to maintain a stable weight and avoid weight loss.
Many patients struggle to maintain a healthy weight. You may not feel like eating or drinking during treatment and some side effects might make it hard to eat. However, making sure you're getting enough calories and combating unwanted weight loss is crucial.
- Eat smaller portions. Colorectal cancer and its treatment affect your body's ability to digest and absorb nutrients. Eating smaller portions of food is easier for your system to digest. If you're having a difficult time eating large meals, try smaller portion sizes every 2-3 hours or supplement with protein drinks.
- Include protein with most meals and snacks. Protein is important for helping the body maintain muscle and heal the damage to healthy cells that can be caused by cancer treatment. It can also help your immune system fight infection and body repair tissues after surgery, chemotherapy or radiation.
High protein foods include poultry, fish, shellfish, beef, pork, eggs, dairy (milk, yogurt, cottage cheese, cheese), nuts, nut butter, lentils, beans and soy products (like tofu, edamame and meat substitutes). - Stay hydrated. The primary function of the colon is to absorb water from the food and beverages that we consume. If you're undergoing radiation or surgery, it can be increasingly difficult for your colon to absorb as much water as it could previously.
Try sipping on water, flavored water, tea, milk, broth, Pedialyte and sports drinks throughout the day to stay hydrated. If you find that sugary drinks lead to loose bowel movements, try watering them down.
- Consume healthy fats. These give the body energy and reduce inflammation, plus they may help the brain and nervous system function properly. They're found in food like fish, seeds, nuts, avocados and olive oil.
- Meet with a specialized dietitian. Cancer treatment is very individualized—and so are the nutrition recommendations for each patient's case. Ask your oncologist for a referral to a dietitian. Some dietitians specialize in oncology nutrition—look for dieticians with the letters “RD, CSO," which stands for Registered Dietitian, Board-Certified Specialist in Oncology Nutrition.
What to avoid during treatment
- Alcohol. It’s okay to drink alcohol on rare occasions, but during treatment, it’s important to limit alcohol consumption as much as possible. Alcohol can interact with many medications and is linked to the development of colon cancer. If you do drink, limit your intake to no more than one (for women) or two (for men) standard drink(s) per day. A standard drink is 12 oz beer, 4 oz wine or 1.5 oz shot of liquor.
- Dietary and herbal supplements. Supplements are often thought of as harmless. However, dietary supplements (including vitamins, minerals, herbals and probiotics) can cause negative impacts during cancer treatment. If you're interested in taking dietary supplements during treatment, make sure to talk to your oncologist or dietitian first.
Navigating challenges and treatment-related side effects
While most patients should strive to follow the general recommendations for good nutrition during cancer treatment, 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, which may require dietary modifications.
Your overall health also impacts your specific needs, so it's essential to consult your doctor or specialist before making significant dietary or lifestyle changes.
