5 min readNov 15, 2025 09:38 PM IST
First published on: Nov 15, 2025 at 10:41 AM IST
For the last 10 years, colorectal cancer specialist Dr Amanjeet Singh has been noticing a change in his patient profiles. “I have been noticing that younger patients between 30s and 40s are getting diagnosed with colorectal cancer, faster than their equivalent demographic in the West. Then I started mapping their lifestyle habits. Fast and ultra-processed foods, convenient, ready-made meals, heat-and-eats, long desk hours, little to no exercise and lack of adequate sleep. In fact, I noticed similar food consumption patterns; almost all of them ate outside or ordered their meals online. That’s why I call colorectal cancer a lifestyle-induced cancer,” says the senior director of GI Surgery and GI Oncology, Gastrosciences at Medanta, Gurugram.
His observation has now been borne out by a study published in JAMA Oncology. It is based on the findings of Dr Andrew T. Chan, a gastroenterologist at Mass General Brigham in Boston, US, that shows how colorectal cancer had spiralled alongside an increased consumption of ultra-processed foods. And that a wrong diet could be triggering this cancer in patients younger than 50. Dr Chan and his team looked at women nurses in their 20s, 30s and 40s. Those who ate more ultra-processed foods, say sugary drinks, fried snacks, processed meats, chips, candies and soda, had a higher risk of developing pre-cancerous polyps or cell clusters growing in the colon or rectum.
What the study found
Researchers followed more than 29,000 female nurses in their mid-20s to early 40s at the start of the study. They tracked them between 1991 and 2015, during which time they filled out detailed dietary questionnaires every four years. All of them had at least one colonoscopy before age 50. Nurses who consumed the most ultra-processed foods (10 servings per day) were 45 per cent more likely to have the most common type of precancerous polyp than those who consumed the least (about three servings per day). The ultra-processed products they had included sliced breads, breakfast cereals, sauces, spreads and artificially-sweetened drinks.
How ultra-processed foods can trigger colon cancer
“Ultra-processed foods are known to disrupt the balance between the good and bad microbes in the gut. This is very important to maintain the protective lining of the intestines. Any damage to it and the toxins cross the gut barrier and lead to inflammation. This leads to abnormal cell behaviour and growth of benign tumours called adenomas at the lower end of the GI tract. Some of these turn malignant,” says Dr Singh.
Overdependence on ultraprocessed and quick-heat foods means low use of fibre. “When you have more fruits, vegetables and home-cooked, planned meals, you have more fibre, which cleans your colon, acting like a scrub brush. This cleans out bacteria and other buildup in your intestines, and reduces your risk for colon cancer,” says Dr Singh.
Which ultra-processed food causes most damage
That, according to Dr Singh, would be processed meat, poultry and fish. Pulverised or minced meat can contain detectable levels of phthalates, which are industrial chemicals that leach into the food during processing and packaging. “If you are not buying fresh, then any meat that comes out of a packet is no-no. Processed meats are most consistently linked to an increased risk of colorectal and stomach cancers. The World Health Organization (WHO) classifies processed meat as a Group 1 carcinogen, meaning there is strong evidence linking its consumption to cancer risk,” says Dr Singh. The nitrites and nitrates used as preservatives can form carcinogenic compounds when the meat is cooked.
Can all polyps in the colon turn into cancer?
Not really but all colorectal cancers start as a polyp, according to Dr Singh. “That’s why we remove any polyp. But at younger ages, most polyps are misdiagnosed as haemorrhoids or piles. In the absence of screening, that polyp, which can be cancerous, grows unnoticed,” he says. Colorectal cancer is slow-growing and symptoms overlap with so many other stomach conditions that many miss early diagnosis, which is crucial to containing the spread when it is in the bowel.
What about screening in India?
There are no India-specific screening guidelines. “But a colonoscopy if you have piles or fissures will reveal if there are precancerous lesions or cell clusters. Colorectal cancers anyway affect Indians a decade earlier than their Western counterparts,” says Dr Singh.
The age for routine screening of colorectal cancer — in people who do not have any symptoms — was reduced by five years to 45 in the US once the incidence went up in the young. “But if a first-degree relative has had colorectal cancer, then the current generation youngster must screen themselves five years before, or at age 40,” says Dr Singh.
There are no India-specific screening guidelines. 
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