Study shows women under 50 face higher risk of colon growths from ultra-processed foods

New research published in JAMA Oncology suggests that consuming ultra-processed foods may increase the risk of developing precancerous colorectal growths in women under 50.

A precancerous colorectal growth is an abnormal lesion in the colon or rectum that can develop into colorectal cancer if left untreated.

The study found that women who consumed an average of three servings of ultra-processed foods per day had a certain risk of developing a precancerous polyp, while those who ate 10 or more servings daily faced a significantly higher risk.

Ultra-processed foods (UPFs) are industrially manufactured foods that often contain ingredients not typically used in home cooking. They are usually made from refined substances such as sugar, oils, starches, and protein isolates, and often include additives like preservatives, flavourings, colourings, emulsifiers, and sweeteners.

High in added sugar, unhealthy fats

Designed to be convenient, long-lasting, and highly palatable, these foods are typically ready-to-eat, ready-to-heat, or ready-to-drink. UPFs are generally high in added sugar, salt, unhealthy fats, and calories, while being low in fibre, vitamins, and minerals.

Examples include sugary drinks such as soda and energy drinks, packaged snacks like chips, cookies, and candy, instant noodles and soups, sweetened breakfast cereals, fast food items including burgers, nuggets and pizza, pre-packaged frozen meals, and processed meats such as hot dogs, sausages, and deli meats, according to the World Health Organisation.

The study followed 29,105 nurses under 50 who had undergone at least one colonoscopy.

A colonoscopy is a medical procedure that allows doctors to examine the inside of the colon and rectum. Using a long, flexible tube called a colonoscope, which has a tiny camera and light at its tip, doctors can look for abnormalities such as polyps, inflammation, or signs of cancer.

Colonoscopies are commonly used to screen for colorectal cancer, investigate symptoms like abdominal pain or rectal bleeding, and remove or biopsy polyps for further testing.

Precancerous growths

Participants were followed from June 1991 to June 2015—about 24 years—and completed dietary questionnaires every four years. Researchers focused on two types of precancerous polyps: adenomas and serrated lesions.

The study also found that participants who consumed more ultra-processed foods tended to have higher body mass index (BMI), were more likely to have a history of smoking, engaged in less physical activity, and consumed fewer nutrients such as fibre and vitamin D.

Every four years, participants reported their dietary intake using detailed food questionnaires, and foods were classified using the NOVA system, which categorises foods based on processing levels.

The main health outcomes were conventional adenomas and serrated lesions, both types of precancerous growths in the colon, confirmed through medical and pathology records.

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• Obesity
• ultra-processed foods
• non-communicable diseases
• cardiovascular disease
• Colonoscopies
• Study shows women under 50 face higher risk of colon growths from ultra-processed foods
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Higher risk

The key finding was that women who consumed the most ultra-processed foods—about 10 servings per day—had a 45 per cent higher risk of developing conventional adenomas compared to women who ate the least—about three servings per day. The researchers noted that the risk increased gradually as UPF intake rose, showing a fairly linear trend. In contrast, there was no significant link between UPF consumption and serrated lesions.

On average, about 35 per cent of daily calories in this cohort came from ultra-processed foods, with a median of 5.7 servings per day. The association between UPFs and conventional adenomas persisted even after adjusting for BMI, diabetes, overall diet quality, fibre intake, calcium, folate, vitamin D, and other lifestyle factors, suggesting that these did not fully explain the link.

The researchers concluded that high consumption of ultra-processed foods may increase the risk of precancerous growths in the colon, which could help explain the rise in early-onset colorectal cancer. They cautioned, however, that the study has limitations: the diet data were self-reported, which can introduce errors; the population was mostly female nurses, which may limit generalisability; and as an observational study, it shows association but cannot prove causation.

Reduce intake

The study emphasises the importance of reducing intake of ultra-processed foods and adopting a healthier, minimally processed diet to potentially lower the risk of colorectal precancerous lesions and early-onset colorectal cancer.

It adds to a growing body of evidence linking ultra-processed foods to numerous health problems, highlighting the long-term risks of frequent consumption. Previous research has associated diets high in UPFs with obesity, type 2 diabetes, high blood pressure, cardiovascular disease, and certain cancers.

Scientists believe these foods may contribute to chronic inflammation, metabolic disruptions, and changes in gut microbiota, all of which can negatively affect the body over time.

The new findings linking ultra-processed foods to precancerous colorectal growths provide further evidence of their potential harm.

Even relatively small increases in daily servings appear to raise the risk, demonstrating how regular reliance on processed foods can quietly affect long-term digestive health. This reinforces public health advice to prioritise minimally processed, nutrient-dense foods such as fruits, vegetables, whole grains, and lean proteins.

In Kenya, the Ministry of Health encourages citizens to reduce consumption of ultra-processed foods and sugary drinks while promoting healthy, balanced diets rich in locally sourced fruits, vegetables, and whole grains.

Similarly, the WHO recommends limiting foods high in added sugar, salt, and unhealthy fats, and increasing intake of fresh and minimally processed foods to reduce the risk of non-communicable diseases, including obesity, diabetes, cardiovascular disease, and certain cancers.