This Simple Shift In How You Think About Food Could Lower Your Colorectal Cancer Risk
Colorectal cancer is the third most commonly diagnosed cancer and the third leading cause of cancer-related death in the United States, and rates are climbing, particularly among adults under 50.
For years, researchers and clinicians have searched for dietary answers, often zeroing in on individual foods: eat more fiber, cut red meat, load up on cruciferous vegetables.
But a new prospective analysis1 of more than 100,000 U.S. adults suggests the bigger picture matters more than any single item on your plate, making a compelling case for rethinking how we approach food and cancer risk altogether.
About the study
Researchers analyzed data from more than 100,000 adults enrolled in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, a large, long-running cancer screening study.
Participants were between 55 and 74 years old at enrollment, and their diets were assessed using a detailed food questionnaire. Over the follow-up period, researchers tracked who developed colorectal cancer and who died from it.
To measure diet quality, the team used the Healthy Eating Index-2020 (HEI-2020), a scoring system developed by the U.S. Department of Agriculture that measures how closely someone's diet aligns with federal dietary guidelines.
Scores range from 0 to 100, with higher scores reflecting a better overall diet. The index evaluates diet quality relative to how much someone eats, not just total food intake.
People with the highest diet quality scores were 39% less likely to die from colorectal cancer
People with the highest diet quality scores were 39% less likely to die from colorectal cancer than those with the lowest scores. Researchers also found that as diet quality improved across the full range of scores, colorectal cancer risk gradually declined.
When researchers looked at specific parts of the colon, they found lower risks for distal colon cancer (the lower portion), a trend toward lower risk for rectal cancer, and a decreasing trend in deaths from proximal colon cancer (the upper portion).
What a high-scoring diet actually looks like
The HEI-2020 scores 13 different components of your diet. A high score rewards eating more of these:
- Total fruits: All fruit, including 100% fruit juice
- Whole fruits: Whole fruit in all forms, excluding juice
- Total vegetables: All vegetables, including legumes
- Greens and beans: Dark green vegetables and legumes in particular
- Whole grains: More whole grains than refined
- Dairy: Milk, yogurt, cheese, and fortified soy beverages
- Total protein foods: Meat, poultry, seafood, eggs, nuts, seeds, and soy
- Seafood and plant proteins: Seafood, nuts, seeds, and legumes within the protein category
- Healthy fats: A higher ratio of unsaturated fats to saturated fats
And penalizes eating too much of these:
- Refined grains: White bread, white rice, and other processed grains
- Sodium: High salt intake
- Added sugars: Sugar added to foods and drinks during processing
- Saturated fats: Found in fatty meats, butter, and full-fat dairy
In practice, a high-scoring diet looks like plenty of fruits, vegetables, whole grains, and legumes, with moderate amounts of lean protein and seafood, and less of the refined, processed, and sugary stuff.
Why fiber may be doing a lot of the heavy lifting
While the HEI-2020 captures overall diet quality, fiber deserves a closer look when it comes to colorectal health. The foods that push HEI-2020 scores higher (whole grains, legumes, fruits, and vegetables) also happen to be the foods richest in dietary fiber.
Fiber supports the colon in a few key ways. It feeds beneficial gut bacteria, which produce a compound called butyrate, the main fuel source for the cells lining your colon.
Butyrate helps keep the gut lining healthy and intact. Fiber also adds bulk to stool and helps move things through your digestive system more quickly, which may reduce the amount of time that potential carcinogens spend in contact with the colon wall.
The study didn't isolate fiber as the specific mechanism behind the results; the HEI-2020 captures the whole dietary pattern, not individual nutrients. But the foods most rewarded by the index are largely the same ones associated with higher fiber intake, making it a plausible and well-supported piece of the puzzle.
Simple ways to nudge your diet quality higher
You don't need a perfect score to benefit. The study suggests that incremental improvements across the full range of diet quality are associated with lower risk, meaning moving from a poor diet to a moderate one may matter just as much as moving from a moderate diet to an excellent one.
A few practical ways to improve your diet quality:
- Swap refined grains for whole grains: Choose whole wheat bread, brown rice, oats, or quinoa instead of their refined counterparts. This single swap improves two HEI-2020 components at once.
- Add a serving of legumes each day: Beans, lentils, and chickpeas count toward both vegetables and plant proteins, and they're among the most fiber-dense foods you can eat.
- Prioritize whole fruit over juice: A piece of fruit provides fiber and scores better on the HEI-2020 than a glass of juice, even 100% juice.
- Cut back on ultra-processed foods: These tend to be high in added sugars, sodium, and refined grains, three components that lower your HEI-2020 score.
- Eat more dark leafy greens: Spinach, kale, arugula, and broccoli are specifically rewarded in the HEI-2020 and bring a wide range of vitamins and minerals along with them.
- Choose seafood twice a week: Seafood is highlighted in the HEI-2020's protein components and is a good source of omega-3 fatty acids, which support broader health.
The takeaway
This study adds meaningful evidence to the case for overall dietary patterns as a driver of long-term colorectal health.
The 39% lower mortality risk associated with the highest diet quality scores is a notable finding, and the gradual trend toward lower incidence across all diet quality levels suggests that even modest improvements to how you eat may carry real benefits over time.