“It is well known that patients with unhealthy diets have increased inflammation in their bodies,” said Dr. Timothy Yeatman, an author of the study and associate center director at the TGH Cancer Institute, said in the press release.  “We now see this inflammation in the colon tumors themselves, and cancer is like a chronic wound that won’t heal.”

Researchers specifically focused on colorectal cancer, the second leading cause of cancer-related deaths overall in the US, according to the American Cancer Society.

They looked at 162 tumor samples from patients at Tampa General Hospital, where they observed an excess number of molecules that promote inflammation—and a shortage of those that reduce inflammation and promote healing.

The study builds on how doctors treat and prevent cancer, with more evidence that shifting diets away from ultra-processed foods—and towards a diet that actively reduces cancer risk.

Here’s what you need to know.

The chronic inflammation-cancer connection

Chronic inflammation is one of the biggest risk factors for cancer, according to the National Cancer Institute. For example, people with chronic inflammatory bowel diseases like ulcerative colitis or Crohn’s disease have an increased risk of developing colorectal cancer.

That’s because over time, chronic inflammation can cause cell mutation and rapid growth—the ideal environment for the development of cancer.

“If your body is living daily off of ultra-processed foods, its ability to heal…decreases due to the inflammation and suppression of the immune system that ultimately allows the cancer to grow,” Yeatman said.

Previous research has established the inflammatory nature of ultra-processed foods themselves, likely from the high intake of sugars, salt, saturated fats and trans fatty acids—staples of a Western diet. Those foods are low in fiber and high in certain omega-6 fatty acids, which have been strongly linked to chronic inflammation and colorectal cancer development and progression.

The USF Health Heart Institute also found in previous studies how an ultra-processed-heavy diet not only increases risk and growth of colorectal cancer, but also plays a role in other diseases, including Alzheimer’s, diabetes and cardiovascular conditions.

“A human’s immune system can be extremely powerful and drastically impact the tumor microenvironment, which is great if harnessed correctly for health and wellness,” Yeatman said in the press release. “But not if it’s suppressed by inflammatory lipids from processed foods.”

What can you do about your cancer risk?

Since the study found an excess of the inflammatory molecules that would come from ultra-processed foods in cancer tumors, a shift in diet is the first step to giving your body the tools to fight cancer growth—namely, a shift towards omega-3 fatty acids.

Omega-3 fatty acids are essential polyunsaturated fats that help your body function properly. They’re particularly concentrated in high levels in your eyes and brain, according to the Cleveland Clinic, and provide vital support for your cardiovascular and endocrine systems.

You can’t naturally produce the amount of omega-3s you need to survive, which is why you have to consume foods rich in them. Some examples are:

• Mackerel
• Salmon
• Chia seeds
• Ground flaxseed
• Walnuts
• Edamame

While omega-3s are important for numerous reasons—including lowering your triglyceride levels, blood pressure, risk of heart disease and stroke, while raising your good cholesterol (HDL) levels—they are particularly powerful in reducing inflammation and cancer risk.

“Our bodies are designed to actively resolve inflammation through bioactive lipid compounds derived from the healthy fats, like avocados, that we consume,” Ganesh Halade, coauthor of the study, associate professor in the USF Health Heart Institute, and a member of the Cancer Biology Program at TGH Cancer Institute, said in the press release.

“Bioactive lipids are very small molecules derived from the foods that we eat and, if the molecules are coming from processed food products, they directly imbalance the immune system and drive chronic inflammation,” Halade said.

If your diet is higher in saturated fats and ultra-processed foods, though, then you have fewer of those good molecules found in polyunsaturated fats that combat inflammation.

The best foods to fight cancer—and foods to stay away from

With these findings that support previous research, medical professionals are increasingly looking to see how diet can treat cancer, or prevent it.

“This has the potential to revolutionize cancer treatment, moving beyond drugs to harness natural healing processes,” Yeatman said. “It’s a vital step toward addressing chronic inflammation and preventing diseases before they start.”

A diet filled with ultra-processed foods is a key factor not just in cancer risk, but growth of cancer cells after diagnosis. Here are some examples of foods you should include in your diet, and ones to steer clear of.

Healthy foods to include, as part of an unprocessed diet:

• Salmon
• Cod
• Spinach
• Brussels sprouts
• Seaweed
• Legumes, like lentils and chickpeas
• Unprocessed soy, like tofu and edamame

Ultra-processed foods to stay away from: 

• Ice cream
• Sausages
• Chips
• Deli meats
• Mass-produced bread
• Breakfast cereals
• Alcoholic drinks