What Fiber Does for Your Risk of Colorectal Cancer

Colorectal cancer is one of the most common cancers in the United States. The good news is that it’s also one of the most preventable.

Staying physically active, limiting your alcohol consumption and keeping up with colon cancer screening can all lower your risk.

Your diet plays an important role, too. And one nutrient in particular can make a big difference: fiber.

What exactly is the link between colorectal cancer and fiber? And how can you make sure you’re getting enough of it? Gastrointestinal medical oncologist Alok Khorana, MD, explains the connection and offers advice.

How fiber may help reduce colon cancer risk

Fiber is the part of plant foods your body can’t fully digest. Instead of being broken down, it moves through your digestive tract.

Along the way, it does a few helpful jobs:

• Moves waste: Fiber helps keep your digestion regular. In other words, it helps you poop. That’s beneficial because when stool stays in your colon too long, it can irritate or damage your intestinal lining. Moving things along may help lower that risk.
• Feeds healthy gut bacteria: A healthy gut microbiome helps maintain balance in your digestive system. It also may reduce inflammation in your colon, which can contribute to cancer development.
• Improves metabolic health: Fiber can help you maintain healthy cholesterol levels, blood pressure and body weight — all factors that influence long-term health, including your cancer risk.

“These benefits don’t happen overnight,” Dr. Khorana notes. “But over time, a diet rich in fiber supports your colon health and promotes healthier systems throughout your body.”

Are you getting enough fiber?

Most adults should aim for about 25 to 35 grams of fiber per day.

But most people in the U.S. aren’t eating nearly enough. Some estimates suggest only about 5% of Americans hit that goal and that, on average, adults in the U.S. consume only about 14 grams of fiber per day.

“Getting enough fiber often requires intentional choices, as many common foods — like red meat, ultra-processed snacks and refined grains — contain very little fiber,” Dr. Khorana says.

Tips to get more fiber in your life

The easiest way to get more fiber in your diet is to eat more whole plant foods. Good sources of fiber include:

• Beans and lentils
• Whole grains, like oats and barley
• Fruits, such as apples and berries
• Vegetables, like broccoli and artichokes
• Nuts and seeds

Dr. Khorana recommends looking for simple opportunities to swap lower-fiber foods for higher-fiber options.

• Choose whole-grain bread and pasta.
• Add beans to salads or soups.
• Snack on fruit or nuts instead of processed snacks.
• Fill half your plate with vegetables.

“Small shifts can add up,” he adds. “When you build meals around plant foods, you naturally increase your fiber intake, which supports both digestive health and overall wellness.”

If you’re struggling to get enough fiber from food alone, fiber supplements may help fill the gap. But they shouldn’t replace a fiber-rich diet.

“Whole foods should always be the first choice,” Dr. Khorana advises. “Supplements can be helpful for some people, but they don’t provide the full range of nutrients you get from fruits, vegetables and whole grains.”

It’s always best to talk with a healthcare provider before starting supplements. They can help you find an option that’s appropriate for your needs and make sure it won’t interfere with other treatments or medications.

Fiber is one piece of colon cancer prevention

While fiber is important, it’s only part of the bigger picture. In addition to getting more fiber in your diet, you can lower your risk of colon cancer by: 

• Exercising regularly
• Maintaining a healthy weight
• Limiting your alcohol consumption
• Not smoking
• Learning about your family cancer history and considering genetic testing, as some colorectal cancers can run in the family
• Keeping up with regular colon cancer screenings, starting at age 45 for people at average risk, or earlier if you have risk factors like a family history of colon cancer or concerning symptoms

“Screening remains one of the most powerful tools we have,” Dr. Khorana emphasizes. “Finding and removing precancerous polyps early can prevent cancer from developing.”

The bottom line

A fiber-rich diet supports healthy digestion, beneficial gut bacteria and regular bowel movements — all factors linked to colon health and lower colon cancer risk.

And most people could benefit from more of it.

“The simplest advice is to eat more plant-based foods,” reiterates Dr. Khorana. “When you prioritize fruits, vegetables, beans and whole grains, you naturally increase fiber. That’s good for your colon and your overall well-being.”