The consumption of ultra-processed foods is related to an increased risk of precancerous colorectal tumors in women under 50 years of age, according to a study published this Thursday in the journal JAMA Oncology.
These tumors, called adenomas or polyps, can later develop into cancer and are a good indicator of a person’s risk of this disease, according to experts.
Rates of colorectal cancer in people under 50 years of age have increased significantly in recent decades. The findings could offer new insights into the causes of this increase.
“One approach we’ve taken is to try to understand what has changed in our environment that might be driving this. What are some of the trends that reflect this acceleration in cancer rates?” said study leader Dr. Andrew Chan, a gastroenterologist and chief of the clinical and translational epidemiology unit at Massachusetts General Brigham in Boston.
Ultra-processed foods now make up the majority of the average American diet, especially among children. These foods, which are often high in calories, have been linked to depression, type 2 diabetes, and premature death. Some experts also suspect that eating this food could be causing increased rates of colorectal cancer among young people.
To test this hypothesis, Chan and her team used data from more than 29,000 women who participated in the Nurses’ Health Study II, an ongoing study of registered nurses started in 1989. The women, who were between 24 and 42 years old when they enrolled in the study, were followed for 24 years, from 1991 to 2015. Every four years, all of them filled out a questionnaire about their diet and underwent at least one colonoscopy before turning 50 years old.
The researchers looked at whether the women had been diagnosed with precancerous polyps: adenomas, which are more likely to turn into cancer, or serrated lesions. Although only about 5% of adenomas are cancerous, about 75% of colorectal cancers begin as adenomas, according to the Cleveland Clinic. Serrated lesions are still considered precancerous, but they are linked to fewer cases of colorectal cancer, Chan added.
The study found a connection between the consumption of more ultra-processed foods and the development of an adenoma before the age of 50. No relationship was observed between food and serrated lesions.
Since most colon cancers originate from adenomas, the study showing an association between eating more ultra-processed foods and a higher risk of developing adenomas gave Chan and his team more confidence that these foods could increase the risk of colorectal cancer, he said.
“The advantage was that we analyzed two main types of polyps: the adenoma type, which seems to be the basis of cancer, and we observed the relationship between the two,” he indicated.
About 1,200 women in the study developed adenomas. Compared with those who ate the least ultra-processed foods, those who ate the most—accounting for a third of their daily calories—were about 1.5 times more likely to develop adenomas. Some specific foods also seemed to increase the risk. Diets higher in sugar and artificial sweeteners were most associated with higher rates of adenomas, followed by diets high in sauces, spreads and condiments.
Although the study only included women, most of them white, other studies have also found a relationship between the consumption of ultra-processed foods and the development of cancer in men.
“We have no reason to believe there is a difference between men and women,” Chan said, adding that to be sure, further research should include men.
Most colorectal polyps do not develop into cancer, but almost all colorectal cancers begin as a polyp, explained Dr. Folasade May, a gastroenterologist and associate professor of medicine at the David Geffen School of Medicine at UCLA, who was not involved in the research.
That’s why doctors remove any polyps they find during a colonoscopy and why people who have polyps are considered to be at higher risk of developing colorectal cancer.
“They are analyzing the first step, who is more likely to develop these polyps that can turn into cancer,” May said of the study.
The problem is that routine screening for colorectal cancer isn’t done until age 45, recalled Dr. Christopher Lieu, co-director of gastrointestinal medical oncology at the University of Colorado Anschutz School of Medicine in Aurora.
“The concern is that when a young person has a polyp, it can grow without being noticed, since these young patients are not screened,” Lieu explained. This makes it even more important to identify modifiable lifestyle factors that are driving rising colorectal cancer rates in young people, added Lieu, who was not involved in the new research.
Although scientists have not yet determined a clear cause, it is unlikely that the increased rates are due to genetic factors, May said.
“This has happened very quickly, so unfortunately it is probably something we have done to ourselves as human beings, by the way we live our lives,” he said. “It is shocking to hear stories every week of people between 20 and 40 years old who suffer from cancers that, when I studied medicine, we were taught only affected people over 80 years old.”
Ultra-processed foods cause inflammation in the intestine, including the colon, which affects the intestine’s ability to repair itself when damaged and keep tumors at bay. High levels of inflammation are also linked to cancer in general, May said. Another hypothesis is that people who consume more ultra-processed foods are more likely to suffer from obesity and type 2 diabetes, both related to a higher risk of colorectal cancer.
“It is most likely the direct toxic effects of these ultra-processed foods,” May said.
Chan, the study’s author, noted that ultra-processed foods are known to alter the gut microbiota, which could theoretically make gut cells more likely to become cancerous.
The next step in the research is to determine whether any of these hypotheses appear to have a causal effect on who develops colorectal cancer at a young age. That’s probably part of the puzzle, Chan insisted.
“One thing that has become clear is that the consumption of ultra-processed foods in the United States has increased greatly in recent decades, reflecting the staggering increase in cases of colorectal cancer,” he concluded.
