Ultraprocessed foods may raise risk of early colorectal tumours that can lead to cancer: Study

A new study has offered fresh insight into why colorectal cancers are rising rapidly among younger adults worldwide — with researchers identifying a strong link between high consumption of ultraprocessed foods and the development of precancerous colorectal growths before age 50.

The findings come as colon and rectal cancer cases among young people continue to surge, particularly in the United States, where ultraprocessed foods now make up 70% of the national food supply and nearly 60% of adult caloric intake, reports CNN.

Published yesterday (13 November) in JAMA Oncology, the study tracked over 29,100 female nurses for a median of 13 years. It found that participants who ate the most ultraprocessed foods — around 10 servings a day — had a 45% higher risk of developing early-age colorectal adenomas compared to those who consumed the least, about three servings a day. Adenomas are noncancerous polyps that can develop into cancer if left untreated.

What the study found

Researchers noted that the biggest sources of ultraprocessed foods among participants were ultraprocessed breads and breakfast items; sauces, spreads and condiments and sugar-sweetened or artificially sweetened beverages

"This study isn't cause and effect, so we can't say this is definitive," said senior author Dr Andrew Chan of Mass General Brigham Cancer Institute. "But it offers clues that what we eat may play a role — and highlights the need to pinpoint which foods or additives pose the greatest risk."

Experts not involved in the study echoed the concerns.

"To the extent possible, you should avoid UPFs and build your diet around whole, minimally processed foods," said Dr David Katz, founder of the True Health Initiative. "The best diets prioritise vegetables, fruits, whole grains, legumes, nuts, seeds and plain water."

Why ultraprocessed foods are harmful

According to the UN Food and Agriculture Organization, ultraprocessed foods are typically high in sodium, added sugars, refined grains, fats, and artificial additives such as preservatives; emulsifiers; flavour and fragrance enhancers, as well as anti-foaming and bleaching agents.

These products often have little fibre and are engineered to be hyper-palatable, which can encourage overeating.

How the study was conducted

The participants were part of the long-running Nurses' Health Study II, which began in 1989. They filled out detailed diet questionnaires every four years. While self-reported data has limitations, researchers say nurses tend to be more accurate than the general population.

Most tumours were discovered before 2015 — before colorectal cancer screening guidelines lowered the initial screening age to 45. This means many participants were likely screened early due to symptoms or family history.

What experts say

Noncancerous colorectal tumours often show no symptoms.

But warning signs may include dark or bloody stools, abdominal pain, iron-deficiency anaemia, unintended weight loss with gastrointestinal symptoms and constipation caused by blockage.

Doctors advise screening from age 45, or earlier for people with a family history of colorectal cancer.

Dr Robin Mendelsohn of Memorial Sloan Kettering Cancer Center said that ultraprocessed foods may disrupt the gut microbiome, damage the intestine's protective lining and contribute to chronic inflammation — all factors linked to cancer risk.

Ultraprocessed foods of the 1990s, when participants were surveyed, differ from those today, said Dr Ganesh Halade of Tampa General Hospital Cancer Institute, due to new additives and changing formulations. Yet one constant has been omega-6-rich seed oils, which he believes may play a key role in rising early-onset colorectal cancers.

The bottom line

Even after adjusting for obesity, diabetes, low fibre intake and other cancer risk factors, the association between ultraprocessed foods and adenomas remained strong.

Experts say the study does not prove causation — but it adds significant evidence that diets high in ultraprocessed foods may be driving the alarming surge of colorectal cancer in younger populations.

They urge people to shift toward minimally processed, whole foods wherever possible — and to remain alert to early symptoms and screening recommendations.