Ultra-processed foods high in seed oils may increase colon cancer risk

The rate of increase in colon and rectal cancer in people under 50 is Recent notable trends This has surprised and perplexed clinicians who are scrambling to figure out why. New research is now being published intestine provides a potentially important insight: specific lipids or fatty acids that are abundant in the body. Ultra-processed foods can promote inflammation and cause colon cancer cells to run wild.

Colorectal cancer tumor samples from 81 people in the U.S. contained too many pro-inflammatory lipids called omega-6 fatty acids and lacked useful lipids called omega-3 fatty acids, which help stop inflammation. I was doing it.

Inflammation is a normal defensive response that the immune system turns on to heal wounds and fight off infections. But researchers in the 1800s discovered that colon tumors looked like “healing wounds” under a microscope, said study co-author Timothy Yetman, a professor of surgery at the University of South Florida. Pervasive inflammation over a long period of time damages cells and impedes their ability to fight the growth of potentially cancerous cells. Yetman suspects that omega-6 fatty acids are often obtained through our diet. ultra-processed foods Probably their main source.

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“While we don't know the full impact of these ultra-processed foods on our bodies, we do know that it has changed significantly since 1950,” says Yetman. “Today's young people, especially the rural poor, are exposed to more processed foods than anyone else because these processed foods are cheap and can be found in every fast food restaurant.”

Many ultra-processed and fast foods are prepared using seed oils. Seed oil is an inexpensive and common type of vegetable cooking oil that is chemically processed from seeds such as canola, corn, grapeseed, and sunflower. These oils are rich in omega-6 fatty acids. However, this study was unable to definitively link the lipids detected in colon cancer tumors to specific foods or oils.

“This study confirms that diet is important, but I think it's probably one of many factors,” said Andrew Chan, a gastroenterologist at Massachusetts General Hospital and a professor at Harvard Medical School. says. He was not involved in this new study. Chan and other researchers point to genetics, exercise, lifestyle, and chemical and environmental exposures as important. May also affect colon cancer risk. Additionally, “the food we eat, how it is transformed, how it is metabolized, and how it ultimately leads to changes in the surrounding tissues, such as lipids, is very complex,” Chan said. says. “So there's still some ground to fill in before we can really tell a cohesive story about it.”

scientific american We spoke with Yetman and Chan to learn more about their findings and the potential role of ultra-processed foods in inflammation and colon cancer.

[An edited transcript of the interviews follows.]

What has past research shown about the relationship between diet and colon cancer?

CHANG: There have been studies in the past that have looked at the association between colorectal cancer risk and certain dietary patterns associated with inflammation. Some of these dietary patterns are also rich in certain types of oils that contain omega-6 fatty acids, which are known to induce inflammation. In contrast, there is data showing that dietary patterns rich in healthier oils, such as the Mediterranean dietary pattern, the so-called prudent eating pattern, appear to be associated with lower risk. Additionally, there were a few things specificthe study These studies have investigated the effects of types of omega-3 fatty acids, such as fish oil, and their potential protective effects on colorectal cancer risk. it has been Mainly shown in animal modelsHowever, there are some clinical trials that suggest there are potential benefits to supplementing your diet with fish oil, for example. Such research still inconsistentSo I think more work needs to be done in this area.

Our group and other researchers are also intrigued by the idea that some of these lipids, which cause cancer-causing inflammation, might be inhibited by drugs such as aspirin. are. Aspirin is an anti-inflammatory drug that specifically targets lipids such as prostaglandins that can promote cancer. These could be useful for developing new cancer prevention strategies focused on altering the balance of these lipids and the balance of inflammatory mediators that may be associated with some of these lipid pathways. It's a step.

How do lipids affect inflammation?

Yateman: When you get a cut on your hand or skin, it initially becomes inflamed and swollen and red, but then it gets better. This is due to resolved inflammation. decomposition of lipidsor degradation-enhancing lipids, were only recently discovered by Charles Sirhan at Harvard University. And he described something called a “lipid class switch.” This means that the body switches from an inflammatory phase to a recovery phase as it undergoes normal healing. He basically discovered that there are a number of these lipids (mainly omega-3 derivative lipids) that lead to resolution of inflammation. However, unchecked inflammation can lead to cancer.

How does this inflammation affect cancer development?

CHANG: Inflammation causes tissue changes that can lead to the development of cancer. When cells have difficulty turning over normally, the tissue is likely to grow uncontrolled, resulting in abnormal cell turnover and excessive cell division that may eventually lead to tumor formation. There is. Inflammation is also known to create an environment that makes tissues more susceptible to changes in DNA, including mutations that can lead to cancer. There may also be inflammatory effects that impair the way the body naturally fights off cancer development.

I suspect that these different lipids and oils have specific effects and pathways related to inflammation and the normal ability of tissues to repair. This may be suitable in environments where uncontrolled cell proliferation can cause some of these tissues to develop into cancer.

Why does an imbalance between pro-inflammatory and pro-recovery lipids occur?

Yetman: The source of these fats is ultimately the diet. Therefore, the overabundance of pro-inflammatory lipids in the tumor microenvironment is a clincher potentially related to the lipids we consume. Levels of omega-6 lipids, the inflammatory side of human body fat, have increased dramatically from the 1950s to today. Perhaps this is due to changes in Western dietary habits. And going back to what that change is, it's ultra-processed foods. Now, ultra-processing doesn't just involve lipids. Lipids are found in many seed oils that are processed and used in food, such as soybean oil, canola oil, cottonseed oil, sunflower oil, and safflower oil. Seed oils are cheap, and as a result, they are present in almost every packaged food we eat. For example, if you go to the store and pull a loaf of unbaked bread from your local bakery off the shelf, you'll notice that it has a whole list of ingredients that are hard to even recognize… And one of them is generally soybean oil. It's in everything from bread, chips, hummus, salad dressings, cookies, cakes, and pies.

It's not just a seed oil. For corn-fed beef, the ratio of omega-6 to omega-3 [can be much higher than that of grass-fed beef]So, a simple change from corn-fed to grass-fed can make a big difference in ratios. However, finding grass-fed beef at the grocery store can be very difficult. The reason is that it costs money. I think it takes three years to market a grass-fed steer, and maybe a year for a corn-fed steer. Therefore, cheaper approaches take much less time.

Do omega-6 fats have a negative effect on your health?

Yetman: Omega-6 is an essential fatty acid. You must have it, but it is not necessary. [a ratio of] 30 times to 1, [compared with omega-3]. So, like everything else, it should be done in moderation. But the problem is that we have vastly exceeded the amount of seed oil in our food. And we get our omega-6s from all sorts of other sources, so I don't think seed oil is necessarily good for you.

Not everyone exposed to seed oil will likely suffer from problems. But I think there's some kind of connection there. These associations are difficult to prove because they require years of people's dietary history. More research is needed and someone needs to prove that the seed oils we consume in excess are indeed safe. And since it's not proven to me yet, I think by default I should reduce them until I figure it out.