If you’re trying to eat healthy, you probably know to tread cautiously in the cookies aisle and frozen foods section at the grocery store. But food surveys show that many U.S. consumers opt for convenience when it comes to mealtime. And a recent study reveals that this big intake of fake food could be harming our colons, especially in men.

Colorectal cancer is the third most common cause of cancer and the second leading cause of death from cancer in men and women A high-fat and low-fiber diet as well as obesity are known risk factors for this cancer. Ultra-processed foods contribute to all these risk factors, and they account for close to 60 percent of the calories in a typical American diet. To examine the link between ultra-processed foods and colorectal cancer, researchers led by Tufts and Harvard Universities in Boston (and including scientists from Brazil and Canada) used three large, long-term health studies that included both detailed diet history and cancer diagnosis.

Processed Versus Ultra-Processed

What are “ultra-processed” foods exactly? Processed foods are a step up from the whole stuff in the produce and meats aisle: There might be some salt or preservative added to keep the product (tuna, canned beans) from going bad. Ultra-processed foods are ready-to-eat items that are made up of multiple ingredients created in laboratories and fabricated to eat right out of the box or bottle (cookies, crackers, sodas, and boxed cereals) or right out of the microwave (frozen “TV dinners”). Besides the usual salt and various sugars, ingredients in ultra-processed items can include a litany of emulsifiers, preservatives, flavors, and colors to enhance the product’s flavor and convenience factor.

What the Three Studies Revealed

The three studies were the Health Professionals Follow-up Study from 1986 to 2014, the Nurses’ Health Study from 1986 to 2014, and the Nurses’ Health Study II from 1991 to 2015. From these studies, the research team identified approximately 160,000 women and 46,000 men who had no evidence of colorectal cancer at the start of the studies and available food questionnaires that were filled out every four years.

Using the food questionnaires, the researchers ranked diets for the amount of ultra-processed foods consumed from the lowest 20 percent to the highest 20 percent of people selected. The results of the study are published in the journal The BMJ. Key results included these findings…

  • During the 24 to 28 years of follow-up, there were 3,216 cases of colorectal cancer.
  • Compared to men in the lowest 20 percent of ultra-processed food consumption, the highest 20 percent of men had a 29 percent increased risk of colorectal cancer.
  • Most of these cancers in men were in the distal or last part of the colon.
  • Foods with the highest risk for men were ready-to-eat meat, poultry, and seafood along with sugar-sweetened beverages.
  • Women only had an increased risk for colon cancer for certain food types: ready-to-eat, heat-mixed dishes (prepared foods that are heated in the microwave), which increased colorectal cancer risk by 17 percent.
  • Women who consumed the most yogurt and dairy-based foods decreased their risk of colorectal cancer by 17 percent.

Why Your Colon Prefers Whole Food

There are many reasons why ultra-processed foods may increase colorectal cancer risk, according to the research team. These foods are high in fats, oils, and sugar that may change the healthy balance of microbes in the colon (the microbiome). Ultra-processed foods are typically low in fiber and increase risk of obesity. They may also have food additives and artificial sweeteners that increase cancer risk. Finally, cancer-causing chemicals may leak into foods from heat processing and plastics used in food packaging.

It’s unclear why women are less at risk from these foods than men. The researchers theorize that women may consume more protective foods like yogurt and other dairy products, and they may use less salt and healthier Mediterranean-diet type foods. Another possible explanation is the female hormone estrogen, which may protect women from cancer.

Subgroups of ultra-processed foods included in the study were…

  • Fat, condiments, and sauces
  • Packaged sweets, snacks, and desserts
  • Artificially sweetened beverages
  • Ready-to-eat, mixed dishes
  • Ready-to-heat meat, poultry, and seafood products
  • Packaged savory snacks
  • Yogurt and dairy-based desserts

This study adds to accumulating evidence that these pre-cooked, instant foods increase the risk of several chronic diseases, including diabetes and cancer. The researchers conclude that their findings support public health measures to limit or discourage the use of ultra-processed foods for better public health outcomes.

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