Certain foods may disrupt your body’s fight against cancer cells, study says

By Sandee LaMotte, CNN

(CNN) — The food you eat may be affecting your body’s ability to fight cancer cells in the colon, according to a new study.

The potential culprit: an overabundance of certain omega-6 fatty acids — perhaps from ultraprocessed foods in your diet — that may hinder the anti-inflammatory and tumor-fighting properties of another essential fatty acid, omega-3.

“There are mutations every day in the GI (gastrointestinal) tract, and normally they’re quashed right away by the immune system with the help of molecules or mediators from omega-3s,” said Dr. Timothy Yeatman, senior coauthor of the study published Tuesday in Gut, the journal of the British Society of Gastroenterology .

“But if you have a body subjected to years of a chronic inflammatory milieu created by an imbalance of omega-6s, the type commonly found in ultraprocessed and junk foods, I believe it’s easier for a mutation to take hold and harder for the body to fight it,” said Yeatman, a surgical oncologist and professor at the University of South Florida and the Tampa General Hospital Cancer Institute.

A Western diet is often high in omega-6 fatty acids, experts say, due to widely available seed oils often used to fry fast foods and manufacture the ultraprocessed foods that now make up about 70% of the US food supply. Linoleic acid, an omega-6 fatty acid that is found in corn, peanut, soybean, safflower and sunflower oils, is the most common omega-6 in the US food supply.

Many people have a significant imbalance of omega-6 to omega-3 in their bodies — a November 2015 study found levels of linoleic acid have increased by 136% in the fat tissue of Americans over the past half century.

“It’s a leap to say that omega-6s from ultraprocessed foods are the cause. Americans have few omega-3s because they dislike fatty fish such as mackerel, herring and sardines, which are great sources,” said Dr. Bill Harris, a professor of internal medicine at the Sanford School of Medicine at the University of South Dakota, who was not involved in the new research.

“Don’t blame the omega-6s, it’s not their fault — it’s the lack of omega-3 fatty acids that’s the problem,” said Harris, who is also the president and founder of the nonprofit Fatty Acid Research Institute in Sioux Falls, South Dakota.

What are essential fatty acids?

Both omega-3 and omega-6 polyunsaturated fatty acids are essential for human health. However, your body cannot make them on its own and must create both from the foods you eat.

Omega-3s — found in high quantities in fatty fish such as salmon as well as flaxseeds and chia seeds, pecans, walnuts and pine nuts — maintain your body’s cells, provide energy, maintain immune defense and reduce inflammation when it’s at optimal levels (like most things, too much omega-3 may be harmful).

Omega-6s are also needed to maintain good health. These molecules stimulate hair and skin growth, regulate metabolism, boost bone health, and in some cases may even be anti-inflammatory.

However, omega-6s can also be converted into molecules such as prostaglandins that signal the initiation of inflammation — not a bad thing when your body is trying to quickly repel an invader or tumor, but devasting if left smoldering for long periods without resolution.

A dangerous trend

Colorectal cancer was traditionally a disease of the old, but no longer. Cancer of the rectum and large intestine is on a deadly march among people as young as age 20, with diagnosed cases continuing to rise among those younger than 50 in the United States and around the world.

Millennials, who were born between 1981 and 1996, have twice the risk of colorectal cancer compared with those born in 1950, according to a February 2017 study. For younger men, this type of cancer is the most deadly; for younger women, colorectal cancer comes in third behind breast and lung cancer, the National Cancer Institute states on its website.

Experts aren’t entirely sure what’s behind the increased risk: Genetics play a role, but the disease is appearing in younger patients with no family history, gastroenterologist Dr. Robin Mendelsohn told CNN in a prior interview.

Rising obesity could explain the rise, but some young patients are vegetarians and exercise fanatics, said Mendelsohn, codirector at the Center for Young Onset Colorectal and Gastrointestinal Cancers at Memorial Sloan Kettering Cancer Center in New York City.

Mounting evidence, however, shows a link between an unhealthy diet high in ultraprocessed foods, red meat and processed meats such as ham, bacon, sausage, hot dogs and deli meat — as well as a lack of fresh fruits and vegetables —to early-onset colorectal cancer, according to the National Cancer Institute.

Resolving inflammation so the body can heal

In the new study, researchers used colorectal cancer tissue harvested from 80 patients in the US and compared the tumor with normal colon tissue taken from the same patient.

The goal: to identify specialized pro-resolving mediators, produced by the body from omega-3 fatty acids, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), during the resolution phase of acute inflammation.

These specialized pro-resolving mediators include resolvins, lipoxins, protectins and maresins, which have potent anti-inflammatory effects that help inflamed tissues return to normal once the need for an inflammatory response is over.

“There are two components to healing from injury or infection,” Yeatman said. “First, the immune system fights the infection with inflammation, like a fever, and then resolves that inflammation with specialized pro-resolving mediators created from derivatives of omega-3s.”

However, omega-3 mediators only come into play when the body is fighting inflammation and are therefore often difficult to detect during the initiation of inflammation, said study coauthor Dr. Ganesh Halade, an associate professor of internal medicine at the University of South Florida. To overcome that obstacle, Halade said he used a highly sensitive analytical technique to identify trace amounts of different mediators from omega-3 in the cancer tumor samples while also measuring levels of omega-6.

“This is the first study to see in a comprehensive way how the molecules coming from omega-3 and omega-6 behave in the cancer tumor and normal control tissue from the same patient,” Halade said.

“We found the control tissue has a perfectly fine balance of molecules from omega-6 and omega-3,” he said. “However, we found a tremendous imbalance in the tumor microenvironment — omega-6 fats coming from ultraprocessed foods were making more proinflammatory molecules inside the cancer tumor, but not in the control tissue.”

Bottom line: Without enough omega-3s available to help control the inflammatory reaction created by the body’s response to cancer, inflammation continues to rage, further damaging cell DNA and prolonging an environment conducive to the cancer’s growth.

“The researchers are basically saying there’s so much omega-6 around that it gives the cancer tumor a chance to just take off, and I think that’s probably correct,” said analytical chemist Tom Brenna, a professor of pediatrics at Dell Medical School at the University of Texas at Austin, who was not involved in the new study.

“As linoleic acid increases in the body, it decreases the amount of two omega-3s, EPA and DHA, in the body’s tissue,” Brenna said. “And Americans don’t get enough omega-3s as it is, so the implication of the study is that if a person has too much omega-6, they likely need to boost their omega-3 to counteract that impact.”

Boosting omega-3 in your diet

Try to obtain as many omega-3s from your diet as you can, experts say. The omega-3s EPA and DHA are found in fatty fish such as anchovies, salmon, mackerel, herring, sardines, sea bass, bluefin tuna and trout. Oysters and mussels are also good sources, according to the American Heart Association.

Eat two servings a week that are about 3 ounces, or about ¾ cup, of flaked fish, the AHA said. Some types of fish, typically larger species such as tuna, contain higher levels of mercury or other environmental contaminants so be sure to vary the types of seafood you eat to reduce risk.

Another important omega-3, alpha-linolenic acid or ALA, is found in nuts and seeds such as walnuts, flaxseeds and chia seeds — with ground flaxseeds and flaxseed oil providing the highest amounts, according to Harvard Medical School’s website. Try sprinkling ground flaxseed or chia seeds on granola and yogurt, and snack on small quantities of nuts during the day.

A good-quality fish oil supplement may also help. There can be side effects from supplementation, such as bad-smelling breath and sweat and headaches, as well as digestive issues such as heartburn, nausea or diarrhea, Harvard’s site stated.

Because omega-3s have anticoagulant effects, experts say it’s always best to check with your doctor before you start taking omega-3s (or any supplement). Suggested limits for various omega-3s vary by age and health conditions — another good reason to check with your doctor.

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