Rates of colon cancer are on the rise for those under the age of 55. As the third most commonly diagnosed cancer, colon cancer ranks second in cancer-related deaths overall and is the leading cause of death in men younger than 50 years old.
However, there is a silver lining. The majority of these diagnoses are preventable. The American Cancer Society (ACS) says that more than half of all cases and deaths are attributable to modifiable risk factors, such as smoking, an unhealthy diet, high alcohol consumption, physical inactivity, and excess body weight.
Good eating habits may be protective. A diet rich in fruits, vegetables, whole grains, nuts, beans, lentils, and fish is associated with lower rates of colon cancer and protection against most cardiometabolic conditions, like heart disease.
Fiber and Cancer
Fiber is a nutritional powerhouse for colon health. The past 30 years of nutrition research analyzed the inverse association between high-fiber diets and colon cancer. Most of these studies found that individuals with a high intake of dietary fiber had a lower risk of colorectal cancer than those with lower consumption.
But how exactly does fiber work its magic? The mechanisms still need to be fully understood, but experts have theories. For one, fiber bulks up stool and speeds up its passage through the body, minimizing the time cancer-causing substances can linger in the colon. It also feeds the good bacteria in the gut, creating specific short-chain fatty acids, like butyrate, which have anti-inflammatory effects in the gut.
Lastly, the healthy plant compounds in fiber-rich foods, like antioxidants, may protect against cell damage and decrease risk.
A 2023 study looked at the dietary habits of 779 people and their respective gut bacteria. Those with higher fiber diets, specifically fiber from whole grain sources, had higher levels of gut bacteria that may lower the risk of colorectal cancer.
Individuals with diets higher in refined grains, like white bread, cornbread, muffins, pizza, and crackers, had lower gut microbiome diversity. Reducing risk means more intact grains, like farro and brown rice, and less refined ones, like high-sugar cereals.
What To Eat
Forget scouring the meat and dairy aisles — fiber is found exclusively in plant foods like fruits, vegetables, whole grains, legumes, nuts, and seeds. No animal products contain this vital nutrient.
Examples of high-fiber fruits include pears, bananas, avocados, and raspberries. Available fresh nearly year-round, pears are packed with fiber — about 6 grams per pear — and are a delicious way to meet fiber needs.
Snacking on a pear provides 21% of the fiber needed in a day. As most of the fiber and antioxidants are found in their skin, enjoy them with the skin on. Try sliced pears with peanut butter for a simple snack, or add them to pizza, salads, smoothies, and whole-grain muffins.
Other high-fiber foods include whole grains, like oats, popcorn, barley, and quinoa, and legumes, like lentils, black beans, chickpeas, and white beans.
Add these foods to most meals and snacks throughout the day to increase fiber intake. Whitney English, Registered Dietitian at Plant-Based Juniors, says these additions can look like “Oatmeal with cinnamon and cooked pears for breakfast, a hummus and vegetable sandwich for lunch, and lentil soup for dinner.”
How Much Is Enough?
What qualifies as a high-fiber diet varies, but the Recommended Dietary Allowance of 22 to 34 grams of fiber per day, depending on age and sex, is likely the minimum. The American Institute for Cancer Research recommends at least 30 grams daily. It suggests that each 10-gram serving of fiber decreases the risk of colorectal cancer by 7%.
That's likely easier said than done. The United States Department of Agriculture (USDA) reports that only 10% of women and 3% of men are getting enough fiber. This is likely because the standard American diet is high in low-fiber foods like refined grains, ultra-processed foods, and sugar-sweetened beverages and low in whole grains, fruits, and vegetables. That same USDA report estimates that only 1 in 10 Americans meets daily fruit and vegetable requirements.
Fiber is not only a weapon against cancer risk; high-fiber diets are associated with better blood sugar control, lower triglyceride levels, and weight loss.
The ACS provides a roadmap to lowering your risk of colorectal cancer, starting with regular screening tests at age 45 for people of average risk. These tests can find colon cancer earlier, when treatments are more likely to be helpful.
As is the case with many diseases, more exercise further reduces risk. The ACS recommends at least 150 minutes of moderate exercise per week, which aligns with the American Heart Association's recommendations. If you currently smoke, quitting can also lower your chance of colon cancer.
That's true with most health recommendations regarding disease prevention: what's suitable for one area is usually good for the other. A fiber-rich diet, regular exercise, maintaining a healthy weight, and avoiding tobacco are lifestyle habits that reduce the risk of other cancers, heart disease, and diabetes.