Research has shown that what you eat can play a large role in your risk for developing colorectal cancer. A recent study also shows that a diet of mostly fruits, vegetables and a moderate amount of fish appears to offer the most protection against developing colorectal cancer.

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The study, published in the journal JAMA Internal Medicine, found a pesco-vegetarian diet — dominated by fruits and vegetables and including a moderate amount of fish — is associated with a 45% reduced risk for colorectal cancers compared to people whose diets include meat.

Researchers at Loma Linda University analyzed the diets of nearly 78,000 people and then compared the diets to cancer incidence rates to estimate the number of people who might develop colorectal cancer.

They found vegans had a 16% lower risk for all colorectal cancers compared to non-vegetarians. Vegans do not eat any foods derived from animals, including dairy products such as cheese, milk and eggs.

The researchers also found that vegetarians had 22% lower risk of colorectal cancer compared to meat-eaters. In general, vegetarians avoid eating meat, but do eat dairy products or certain dairy products such as eggs.

But, the researchers found, the pesco-vegetarian diet appears to offer the most protection against colorectal cancer. A pesco-vegetarian is a vegetarian who also consumes fish and seafood.

The importance of fiber

Studies have linked red meat, especially processed meat, to increased risk of colorectal cancer. This is especially true for processed meat, which is meat preserved by smoking, curing, salting, or adding chemical preservatives. Examples of processed meat include bacon, ham, sausage and hot dogs.

At the same time, foods that contain high amounts of fiber have been linked to decreased risk of colon cancer. Researchers believe that may be because fiber tends to add bulk to your digestive system, shortening the amount of time that wastes travel through the colon.

As this waste often contains carcinogens, a high amount of fiber decreases the opportunity for carcinogens to affect the intestinal cells, says colorectal surgeon Scott Steele, MD. Dr. Steele did not participate in the study.

“All sources of fiber would be beneficial, though fruits and vegetables are a readily available — and in most cases, delicious — source,” Dr. Steele says.

“They have multiple benefits throughout the body, including helping out with lowering blood sugar and cholesterol,” he says. “For the gastrointestinal tract, they help transit time of waste products through the colon and even help with improving symptoms of hemorrhoids.”

Diet decisions

The study noted that a Mediterranean-style diet, with its emphasis on fish and fresh fruits and vegetables, was a good example of a pesco-vegetarian diet. The study results showed a Mediterranean-style diet lowered colorectal cancer risk by 43%, compared to a non-vegetarian diet.

Recently, the Dietary Guidelines Advisory Committee recommended all Americans eat a Mediterranean-style diet, or a diet that provides about 30% of its calories from fat. In addition to seafood, fruits and vegetables, the Mediterranean diet emphasizes whole grains, beans, nuts and olive oil.

Adding seafood to your meal-planning can make it easier to meet your daily nutrient needs while still maintaining a mostly plant-based diet, Dr. Steele says.

“It just goes back to what we’ve been learning over time. The Mediterranean Diet is a really healthy diet,” Dr. Steele says. “It keeps us from developing things such as colon and rectal cancers, heart disease and other diseases.”