Why are more millennials getting colorectal cancer despite healthy lifestyles? Should you get a colonoscopy?

Article first published on Channel News Asia

Say what you will of millennials but you’ve got to hand it to them for single-handedly popularising TikTok, avocado toast and Taylor Swift. The Class of 1981-1996 (between 28 and 43 years old) has also graduated with honours for successfully sliding millennial slang into the DMs that have now become common phrases – and YOLO-ing them to their full potential because, you know, FOMO.

Speaking of fear of missing out, another thing that defines millennials is that they are high-key woke about their health. At least according to a study by market research firm Nielsen. They may be younger than boomers and Gen X-ers but they are buying more health supplements as well as gluten-free and organic products to clap back at diseases later in life.

So, it might come as a surprise to hear that colorectal cancer, which affects the colon and rectum, is on the uptick among this generation, according to some doctors.

While “there has been a steady decline in (colorectal cancer) incidence for the last few decades”, it is “only restricted to people above the age of 55”, said Dr Melvin Look, a consultant surgeon in gastrointestinal and laparoscopic surgery at PanAsia Surgery.“For those younger than 55, we have, in fact, seen a 50 per cent increase in incidence from 1994 to 2014.”

It’s a trend that Dr Ganesh Ramalingam, the medical director and a specialist in general surgery at G&L Clinic, has also noted. “In 2019, around 20 per cent of colorectal cancer diagnoses were made in patients under age 55, which is double the rate back in 1995.”

There’s also been a steady 3 per cent annual rise in advanced disease among those under 50, he said. “When we look at millennials specifically, they’re facing double the risk of colorectal cancer compared to those born in 1950.”


Whether you’re a boomer, Gen X-er or millennial, cancer of the colon and rectum doesn’t discriminate. It is the leading cause of cancer death for men under 50, and the second-leading cause for women in the same age group.

Widely accepted factors include foods high in sodium, excessive sugar intake, lack of fibre as well as conditions such as irritable bowel syndrome (IBS) and chronic constipation. Being chronically stressed and sedentary play a part, too; stress can induce cancer-causing inflammation, while the lack of exercise slows down your bowel action. 

But how did millennials become its unfortunate poster boys and girls since their health is supposedly on fleek? After all, those who have been active as adolescents and stayed so into adulthood were found to be 24 per cent less likely to develop a precursor to colon cancer, according to a study in British Journal Of Cancer. Even late bloomers who only started exercising in adulthood showed a 9 per cent drop in risk.

And it’s not just health-conscious millennials apparently. Curiously, “there is also a group of very fit and healthy people who are getting colorectal cancer”, said Dr Look, referencing a study that looked at the link between ultramarathoners and increased colorectal cancer risks.

The ongoing study stated that when elite endurance athletes run for upwards of six hours, their bodies re-route a significant amount of blood from the gut to the muscles in their legs. This loss of blood flow to the gut is suggested to cause ischaemia, resulting in cellular damage and a more disorderly and rapid process of cell turnover.

“When it comes to the curious phenomenon of seemingly healthy individuals developing colorectal cancer, genetic predisposition and family history may come into play in some cases,” said Dr Ganesh.

It could also come down to the gut microbiome, said Dr Look. “(The gut microbiome) refers to the trillions of beneficial bacteria and micro-organisms that live in our intestines, which collectively forms a complex ecosystem that plays a part in our immune system.”

He continued: “It is postulated that some sort of environmental change is behind this, possibly affecting our gut microbiome. Damage to our gut microbiome, for example, from excessive and unnecessary intake of antibiotics when we were young, may impair gut immunity and make it less effective in removing pre-cancerous mutations in our colon cells”.

Shifts in diet can also “alter the composition of the gut microbiome, potentially making individuals more susceptible to colorectal cancer”, added Dr Ganesh.


A polyp is a little nub of tissue that grows from a mucous membrane, and can develop in the colon and rectum. It is the thing that your gastroenterologist looks for when he’s performing a colonoscopy as they can develop into cancer.

“The likelihood of detecting pre-cancerous polyps in a person above the age of 50 for the first time is more than 30 per cent for males and 20 per cent in females”, said Dr Look. In millennials or those below age 50, the chances of finding polyps during a colonoscopy is much lower, he said. “Even if they are present, they are unlikely to be the pre-cancerous type.”

“While the transformation (from benign polyp to cancerous tumour) can take several years, there’s no fixed timeline,” said Dr Ganesh, “which makes regular screenings very important for early detection and prevention.”


The large intestine is a muscular tube measuring about 150cm in length and consists of:

  • Ascending colon: The colon starts here and goes up the right side of your abdomen before turning 90 degrees to the left.
  • Transverse colon: This portion goes across your abdomen from right to left before it makes another 90 degrees to go downwards.
  • Descending colon: The colon then comes down the left side of your abdomen.
  • Sigmoid colon: Here’s where the colon curves into a 40cm S-shape.
  • Rectum: This is the 15cm straight stretch before the colon joins with the anus.

“Colorectal cancer can form in any of these parts but the left side, especially the rectum and sigmoid colon, tend to be the commonest areas where they form,” said Dr Look.

Right-sided cancers, on the other hand, tend to occur more in women and older people, he said. “They are also more aggressive and have worse outcomes compared to left-sided cancers.”


Our genes become more “accident prone” as we grow older, said Dr Look. “That’s why most polyps start to form when we hit our 40s.”

Genetically, there are three potential explanations why a small, fleshy nub in your large intestine decides to become malignant, said Dr Wong Soong Kuan, a general surgeon with The Colorectal Clinic:

1. Genetic damage

The accumulation of DNA damage sustained by colon cells, in addition to altered tumour suppressor genes, may result in uncontrolled cell growth. This is the most conventional cause and occurs in 70 per cent of cases.

2. Methylation pathway

The normal genes are switched off, leading to the growth of serrated polyps, so named for their shape. These polyps can occur in 20 per cent to 30 per cent of cases.

3. Microsatellite instability

The dysfunction of repair genes, which are responsible for fixing genetic defects, can lead to cancer. Such tumours are often on the right side of the colon and diagnosed in 30 per cent of cases.


There is no difference in the colorectal cancer detected across the ages,” said Dr Wong. Also, “whether or not polyps have a high chance of developing cancer is independent of age” and more on these factors:

Size: There is a 50 per cent chance of a polyp becoming cancerous when it is larger than 2.5cm; hence, the importance of removing them while small.

Shape: Pedunculated polyps have a stalk that connects the polyp to the intestinal lining. When removed, they usually do not recur. On the other hand, flat or sessile polyps merge into the intestine lining, making them easier to invade the intestine wall.

Number of polyps: The greater the number of polyps, the higher the incidence of cancer.

Cell type: Adenomatous polyps are pre-cancerous. Hyperplastic polyps are usually benign.

According to Dr Wong, the survival rate depends only on the stage of the cancer. Unfortunately, “more than 50 per cent of colorectal cancer cases are detected in an advanced stage (eg. Stage III or IV)”.

“This is mainly due to the fact that by the time symptoms are present – a change in bowel habits, abdominal pain or bloating, more than 10 per cent weight loss, and abnormal yet visible rectal bleeding – the cancer has grown to a large size,” he said.


While colonoscopy is recommended in “average-risk patients above age 50 without any symptoms”, Dr Wong suggests making an appointment for one if you have:

  • A first-degree relative who has colon cancer or polyps.
  • Two relatives who have colon cancer or polyps, irrespective of degree.
  • A personal history of inflammatory bowel disease such as Crohn’s or ulcerative colitis.
  • A personal history of colon polyps.

“Although most colorectal cancers develop sporadically 90 per cent of the time, as many as one in three people who develop colorectal cancer have family members who have developed colorectal cancer,” said Dr Wong. “The risk is even higher if that relative was diagnosed with cancer when they were younger than 50, or if more than one first-degree relative is affected.”

n general, if there is a family history of colorectal cancer, screening should begin at least 10 years before your relative’s case was detected or from age 50 onwards, whichever is sooner, advised Dr Wong. “And intervals of five to 10 years are necessary, depending on whether polyps are found.”

The same applies if you have a strong family history of other cancers with associated genetic risk such as stomach, breast or uterine cancers, said Dr Look.

“Pay attention to your body,” said Dr Ganesh. “If you’re dealing with symptoms like rectal bleeding, persistent changes in your bowel habits, abdominal pain or unexplained weight loss, don’t brush them off. They could be red flags for something more serious.”

And that’s no cap.