The number one diet change experts highly recommended to lower your cancer risk

The American Association for Cancer Research estimates that lifestyle modifications can prevent 40% of all cancers. In the United States, 20% of cancer diagnoses are linked to excess body weight, bad food choices, alcohol consumption, and physical inactivity.

Experts believe that most Americans are deficient in one essential ingredient that might significantly increase your chance of developing cancer.

Getty Images 

Eating habits are one of the most modifiable variables in decreasing cancer risk. Six of the American Institute for Cancer Research's ten cancer prevention guidelines are dietary-based. While maintaining a healthy diet is important, researchers believe that most Americans are deficient in one essential ingredient that might significantly increase your chance of developing cancer: fiber.

"If people are thinking about, 'How can I optimize my health and reduce my risk of cancer,' fiber is what we should be focusing on," says Dr. Amy Comander, Medical Director of Mass General Cancer Center-Waltham.

The United States Dietary Guidelines indicate that women consume 22 to 28 grams of fiber per day, while men ingest 28 to 34 grams of fiber per day. According to the American Society for Nutrition, just 5% of men and 9% of women meet that goal, with the typical American consuming only 10 to 15 grams of fiber per day.

"Diet has a big impact on our wellness in general," says Dr. Andrea Tufano-Sugarman, gynecologic medical oncologist at Memorial Sloan Kettering Cancer Center. "I tell my patients, food is medicine."

How can fiber help reduce cancer risk?

A high-fiber diet has a direct association with improved gut health, Tufano-Sugarman says. 

"The more fiber you eat—the more fruits, vegetables, legumes, whole grains—the more diverse your microbiome is," says Tufano-Sugarman. This reduces the risk of cancer, particularly colorectal cancer, by lowering the chance of chronic diseases and inflammatory disorders in your gastrointestinal tract, she adds.

Dr. Nigel Brockton, Vice President of Research at the American Institute for Cancer Research (AICR), believes that improving your gut health can also help to boost your immune system. A stronger immune system will provide your body with the skills it needs to fight against possibly malignant cells, he adds.

Plant-based foods such as whole grains, fruits, vegetables, beans, nuts, and seeds are high in fiber and can help reduce your risk of obesity, which is a key risk factor for cancer, according to Brockton.

That's because plant-based meals are inherently lower in calories, and their fiber content keeps you satiated for longer. This reduces your odds of consuming too many calories, Brockton says, while also allowing you to consume more whole foods rather than ultra-processed items like deli meat and packaged snacks, which the AICR has linked to an elevated risk of numerous malignancies.

How to include extra fiber in your diet

Experts agreed that a plant-based, fiber-rich diet that limits or eliminates alcohol, red meat, and processed meat is the best way to help prevent cancer.

Here are expert-backed tips to simply increase your fiber intake:

1. Brockton recommends replacing refined carbohydrates like as pasta, white rice, and white bread with high-fiber, whole-grain alternatives.

2. Comander suggests that you fill half of your plate with veggies.

3. Tufano-Sugarman recommends eating the least processed variety of vegetables, such as baked potatoes instead than French fries. 

4. Choose foods high in sulforaphane, a chemical that has been linked to anticancer effects, according to Tufano-Sugarman. Cruciferous vegetables such as arugula, brussels sprouts, broccoli, cauliflower, and kale can be eaten raw, lightly cooked, or steamed, she says.

Michael Pollan, the author of Food Rules, coined the simple motto that Comander reminds her patients: "Eat food, not too much, mostly plants."