Research shows that women under 50 whose diets are high in ultra-processed foods (UPF) are at greater risk of developing abnormal growths in the intestines that can lead to cancer.
Ultra-processed foods are generally defined as industrially produced foods that are often ready-to-eat, low in whole foods, fiber and vitamins, and typically high in saturated fat, sugar, salt and additives.
Bye this concept is not without controversynot least regarding whether all UPF are harmful to health, research has shown that such products associated with many health problemsfrom a higher risk of heart disease to earlier death.
Now researchers say women who consume more UPF have a greater risk of early onset of a common type of intestinal polyp known as common adenomas.
Dr Andrew Chan, lead author of the study at Massachusetts General Hospital in the US, said the study was driven by an attempt to understand What has contributed to the rise in bowel cancer incidence in young people?.
“The vast majority of these polyps do not develop into bowel cancer. But at the same time, we know that the vast majority of bowel cancers that we see in young people arise from these pre-existing lesions,” he said.
Published in the journal Jama Oncology.Chen and his colleagues describe how they examined data collected as part of the second US Nurses' Health Study (NHS II), which began in 1989 and included female nurses born between 1947 and 1964.
Since 1991, participants have been asked to complete a dietary questionnaire every four years, in which they report how often they ate various foods in the previous 12 months.
The team looked at data from 29,105 participants who completed questionnaires, had a colonoscopy at some point after 1991, and had no history of polyps, inflammatory bowel disease, or any type of cancer other than nonmelanoma skin cancer.
These participants were followed until June 2015, when they all reached the age of 50 years. By that time, 1,189 cases of common early-onset adenomas and 1,598 cases of another type of polyp known as a serrated lesion had been reported.
The team divided participants into five equally sized groups based on their UPF intake and found that compared to the group that ate the least UPF—an average of 3.3 servings per day—the group that ate the most—an average of 9.9 servings per day—had a 45% greater risk of developing common early-onset adenomas when factors such as BMI, smoking, and physical activity were taken into account.
However, there was no associated risk of developing serrated lesions.
The study has limitations, including that it is based on participants' memories of food, may be complicated by difficulties with classifying foods as UPF, does not account for the development of bowel cancer itself, and cannot prove that UPF cause the development of polyps.
However, Chen said there are several plausible mechanisms that could explain the results, noting that UPFs are associated with metabolic disorders associated with obesity and type 2 diabetes, which are associated with an increased risk of colorectal cancer. He also said that UPFs may contribute to an overall state of chronic inflammation or may affect gut microbes and the intestinal lining.
Chan said that while it is likely that the results would hold true for men, more research is needed.
“This doesn't mean that if you eat UPF you'll inevitably get cancer. That's definitely not our message,” he said. “But it's a piece of the puzzle in terms of what might influence cancer rates.”
Fiona Osgun, Head of Health Information at Cancer Research UK said that while the study did not directly measure cancer risk, it provided useful information about how diet may influence early changes in the gut that sometimes lead to cancer.
Osgun added that policy changes are needed to make healthier diets more accessible to everyone. “Our overall diet matters more for cancer risk than any single type of food,” she said.
