Fiber and Colon Cancer Risk: What You Need to Know

Could your morning bowl of oatmeal – or your choice of sandwich bread – actually lower your risk of colon cancer? According to research and leading physicians, the answer is yes.

Colon cancer is the second leading cause of cancer death in the United States, according to the American Cancer Society. But there's good news: up to 55 percent of colorectal cancers may be preventable through diet and lifestyle changes, and one of the most powerful changes you can make is getting more fiber.

“Research consistently shows that a high intake of dietary fiber, especially from whole plant foods such as fruits, vegetables, legumes and whole grains, is associated with a reduced risk of colon cancer,” says Glenn S. Parker, M.D., FACS, FASCRS, a specialist in colon and rectal surgery and gastrointestinal surgical oncology at Jersey Shore University Medical Center and Ocean University Medical Center. 

How Fiber Protects Against Colon Cancer    

Fiber does more than just keep you regular. When you eat fiber-rich foods, especially plant-based ones, it helps your body in a few protective ways:

• Promotes regular bowel movements that help keep your digestive system clean and moving.
• Dilutes and speeds up the removal of potential carcinogens (substances that can cause cancer) from the colon before they can do harm.
• Feeds your beneficial gut bacteria, which in turn produce short-chain fatty acids that help reduce inflammation and protect colon cells.

“These short-chain fatty acids, such as butyrate, are made when fiber ferments in the gut and they’ve been shown to have protective effects on colon cells,” Dr. Parker explains. 

Small Changes That Make a Big Impact 

Protecting your colon health doesn’t mean completely overhauling your diet. Even a few smart, consistent changes can go a long way in reducing your colon cancer risk. Here’s how to start:   

Know how much fiber you actually need

Most people aren’t getting enough fiber, and much of the time, they don’t even realize it. According to the U.S. Department of Agriculture (USDA):

• Women should aim for at least 25 grams of fiber per day
• Men should aim for at least 38 grams of fiber per day

In reality, the average American only consumes around 16 grams daily. That’s far below what’s needed for optimal gut and colon health.

Boost your dietary fiber intake by including a fiber-rich food at every meal. Here’s an example of a fiber-filled day:

• Breakfast: Oatmeal with berries or ground flaxseeds
• Lunch: A salad with chickpeas and avocado
• Dinner: Stir-fry made with vegetables, tofu and brown rice
• Snacks: A handful of almonds, or apple slices with peanut butter

And remember: when increasing your fiber, it’s also important to drink more water to help your digestive system adjust and function smoothly.

Choose whole foods over fiber supplements  

Fiber supplements may seem like a quick fix, but when it comes to cancer prevention, whole foods are the better choice.

“A common misconception is that fiber supplements alone offer the same protective benefits as fiber from whole foods,” says Dr. Parker. “While supplements such as psyllium can help with constipation, they don’t provide the same array of nutrients, antioxidants and phytochemicals found in fiber-rich whole foods.”

Instead of reaching for a supplement, look to foods such as:

• Fresh fruits and vegetables
• Legumes like lentils, chickpeas and black beans
• Nuts and seeds
• Whole grains such as brown rice, oats and quinoa

Whole foods do more than increase fiber – they deliver powerful plant-based compounds that help reduce inflammation and protect your cells.

Make simple swaps at mealtime  

Adding more fiber to your diet doesn’t need to be complicated. Start with easy, sustainable swaps like:

• Adding beans to soups, salads or pasta dishes
• Choosing whole wheat bread over white bread
• Replacing white rice with brown rice or farro
• Snacking on raw veggies, nuts or air-popped popcorn instead of chips 

“One realistic and impactful change is to exchange refined grains like white bread or white rice with whole grains like oats, brown rice or whole wheat bread,” Dr. Parker says. “This simple shift increases fiber intake and provides additional nutrients without requiring a complete change in diet.”

Final Takeaways on Fiber & Colon Cancer Risk  

Colon cancer is common, but often preventable. Here’s what you should remember:

• High fiber intake from whole foods can reduce your risk of colon cancer.
• Supplements aren’t a substitute for a healthy, plant-based diet.
• Even small changes – like swapping white bread for whole wheat – can make a difference.

“Start small and build from there,” says Dr. Parker. “Improving your diet doesn’t have to be overwhelming. It’s about making smart, sustainable choices that support your long-term health.”

If you’re ready to take action, talk to your doctor or a registered dietitian about easy ways to add more fiber to your meals. It’s a great step to protecting your colon health for years to come.  

Next Steps & Resources

• Meet our source: Glenn Scot Parker, M.D.  
• To make an appointment with a doctor near you, call 800-822-8905 or visit our website.
• Learn more about our colorectal surgery services, cancer care or gastroenterology services.

The material provided through HealthU is intended to be used as general information only and should not replace the advice of your physician. Always consult your physician for individual care.