Illustration showing colorectal cancer
Credit: Mohammed Haneefa Nizamudeen/Getty Images

The convenience of pre-cooked and instant meals may make it easy to overlook their less-than-ideal nutritional value, but a team led by researchers at Tufts University and Harvard University hope that will change after recently discovering a link between the high consumption of ultra-processed foods and an increased risk of colorectal cancer.

In a study published recently in The BMJ, researchers found that men who consumed high rates of ultra-processed foods were at 29% higher risk for developing colorectal cancer—the third most diagnosed cancer in the United States.

“Ultra-processed foods contribute to a large percentage of daily calories that Americans consume—57% in adults and 67% in children,” lead author, Fang Fang Zhang of Tufts told Inside Precision Medicine. “An increasing number of studies have reported a link between ultra-processed food consumption and adverse health outcomes, including an increased risk of some cancers.”

“We started out thinking that colorectal cancer could be the cancer most impacted by diet compared to other cancer types,” said Lu Wang, the study’s lead author, from Tufts. “Processed meats, most of which fall into the category of ultra-processed foods, are a strong risk factor for colorectal cancer. Ultra-processed foods are also high in added sugars and low in fiber, which contribute to weight gain and obesity, and obesity is an established risk factor for colorectal cancer.”

This study analyzed responses from more than 200,000 participants, including 159,907 women and 46,341 men. These subjects participated in three large prospective studies that assessed dietary intake and were conducted over the course of more than 25 years. Each participant was provided with a food frequency questionnaire every four years and asked about the frequency of consumption of around 130 foods.

The studies this research is based on include:

For this BMJ study, participants’ intake of ultra-processed foods was then classified into quintiles, ranging in value from the lowest consumption to the highest. Those in the highest quintile were identified as being those most at risk for developing colorectal cancer. Although there was a clear link identified for men, particularly in cases of colorectal cancer in the distal colon, the study did not find an overall increased risk for women who consumed higher amounts of ultra-processed foods.

The analyses revealed differences in the ways that men and women consume ultra-processed foods and the prospective associated cancer risk. Of the 206,000 participants followed for more than 25 years, the research team documented 1,294 cases of colorectal cancer among men, and 1,922 cases among women.

The team found that the strongest association between colorectal cancer and ultra-processed foods among men came from meat, poultry, or fish-based, ready-to-eat products. “These products include some processed meats like sausages, bacon, ham, and fish cakes. This is consistent with our hypothesis,” Wang said.

The team also found higher consumption of sugar-sweetened beverages, like soda, fruit-based beverages, and sugary milk-based beverages is associated with an increased risk of colorectal cancer in men.

However, not all ultra-processed foods are equally harmful with regard to colorectal cancer risk. “We found an inverse association between ultra-processed dairy foods like yogurt and colorectal cancer risk among women,” said co-senior author Fang Fang Zhang, a cancer epidemiologist and interim chair of the Division of Nutrition Epidemiology and Data Science at the Friedman School of Nutrition Science and Policy.

“Cancer takes years or even decades to develop, and from our epidemiological studies, we have shown the potential latency effect—it takes years to see an effect for certain exposure on cancer risk,” said Song. “Because of this lengthy process, it’s important to have long-term exposure to data to better evaluate cancer risk.”

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