Ultra-processed foods and cancer: Women under 50 who rely heavily on ultra-processed foods may face a higher risk of developing bowel growths that can later turn cancerous, a new study suggests.
Ultra-processed foods (UPFs) are industrially made products that are usually ready-to-eat, low in whole ingredients, fibre and vitamins, and typically high in sugar, salt, unhealthy fats and additives. Though there is ongoing debate about whether all UPFs are equally harmful, previous research has linked high consumption to heart disease, obesity and even early death.
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The latest findings, published in JAMA Oncology, point to a link between high UPF intake and the early onset of a common type of bowel polyp called a conventional adenoma. These polyps are not cancerous themselves, but many bowel cancers in younger adults are thought to start from such precursor lesions.
“We wanted to understand what’s behind the rising rates of bowel cancer in younger people,” said Dr Andrew Chan of Massachusetts General Hospital, who led the study. “Most of these polyps will never become cancer, but most cancers we do see in young adults start from them.”
The team analysed data from the long-running US Nurses’ Health Study II, which has tracked the health of female nurses since 1989. They focused on 29,105 women who had no history of polyps, inflammatory bowel disease or major cancers (other than non-melanoma skin cancer), had filled out detailed food questionnaires every four years from 1991, and had undergone at least one colonoscopy.
By June 2015, when all participants had reached 50 years of age, researchers had recorded 1,189 cases of early-onset conventional adenomas and 1,598 cases of another type of polyp called serrated lesions. When the women were divided into five groups based on how much UPF they ate, a clear pattern emerged: those in the highest-intake group, averaging about 9.9 servings of UPFs a day, had a 45% higher risk of early-onset conventional adenomas compared with those in the lowest-intake group, who ate about 3.3 servings a day. The association held even after adjusting for body mass index, smoking, physical activity and other lifestyle factors. No similar link was seen for serrated lesions.
The study has important caveats. It relied on self-reported diet, which can be inaccurate; classifying foods as “ultra-processed” is not always straightforward; and the research looked at polyps, not bowel cancer itself, so it cannot prove that UPFs directly cause cancer.
Even so, Chan said there are biologically plausible reasons for the association. High UPF intake has been tied to obesity and type 2 diabetes, both known risk factors for bowel cancer, and may also drive chronic inflammation or alter the gut microbiome and the gut lining. He added that although the work focused on women, similar patterns would be seen in men.