More young people are getting colon cancer. Here is what you can do to protect yourself

Do you want the good news, or the bad news? The good news is that the rates of colon cancer in the over-50s are falling. The bad news? Cases of colon cancer, also known as bowel cancer, are rising in younger people, with numbers more than doubling in Australia since 2000. Australia now has the highest rates of reported early-onset colon cancer among 50 countries worldwide.

While the falling rates in older Australians have coincided with the introduction of the National Bowel Cancer Screening Program, attention is now turning to the alarming rise among young people, with one in nine Australians diagnosed with bowel cancer being under the age of 50.

Australia has the highest rates of colon cancer in people under 50 in the world.Credit: Getty Images/Science Photo Library RF

The list of suspects for the increase is long, but rising rates of obesity and inactivity in younger adults are major contenders, says Professor Karen Canfell, professor of public health at the University of Sydney.

“There’s already good evidence that they can cause colon cancer, and a major line of inquiry is the extent to which under 50s are now affected by them – it’s likely to explain part of the phenomenon.”

Diet, alcohol, smoking, early exposure to antibiotics, and infection from E.coli bacteria are other suspects. So is a relative newcomer: microplastics, those invisible fragments of plastic in food and water that can end up inside us, say a group of researchers and colorectal surgeons from Monash University and Cabrini Health in Melbourne.

Not-so-fantastic plastic

Reading their recent summary of what’s known so far about the impact of microplastic in the gut in the ANZ Journal of Surgery makes you regret ever sipping water from a plastic bottle or diving into a takeaway container of green curry – especially when you learn that adults consume up to 52,000 particles each year, with babies and small children potentially taking in more via plastic drink bottles.

“We’re seeing more young patients with rectal and distal colon cancer, often without the usual risk factors. This motivated us to explore whether microplastics could contribute in some way,” says senior author Dr Vignesh Narasimhan, a colorectal surgeon at Monash Health and Cabrini Hospital.

Colon cancer starts in the lining of the bowel, and studies have now found that microplastics may disrupt this lining’s frontline defence – a delicate layer of mucus that protects it from harmful microbes and toxins, says lead author Dr Rathin Gosavi, colorectal fellow at Cabrini Hospital.

“The thinning or patchiness of this mucus layer can leave the underlying cells exposed, increasing the risk of inflammation and, potentially, damage from microbial by-products. Microplastics might also disturb the balance of ‘friendly’ bacteria that produce compounds that protect the gut, and may provide surfaces for harmful bacteria to form biofilms – sticky layers of bacteria, some of which release toxins implicated in colorectal cancer.”

Still, the group is careful to stress that it’s early research: more studies are needed to confirm a clear link between microplastics and cancer.

“Most of what we know comes from experimental models, in animals and cell systems, showing that microplastics can disrupt gut barrier function, alter the microbiome, and promote inflammation. A few small human studies have detected microplastics in colorectal tumour tissue, but we’re far from proving causation. At this stage, it’s a hypothesis worth testing, not a conclusion.”

A diet rich in whole grains and low in processed food has been linked to a lower risk of cancer. Credit: Getty Images

How can we keep our gut in the best possible shape?

• Staying at a healthy weight is a good start – each year, overweight and obesity cause almost 5300 cases of cancer, including colon cancer, while physical inactivity causes 12 per cent of our colon cancers, according to Cancer Council Australia.
• Eat minimally processed foods like whole grains, legumes, vegetables, fruit and unsalted nuts – but less red and processed meat. There’s strong evidence that it causes colon cancer. The haem iron content of meat is thought to be one culprit – it makes meat red but also forms harmful N-nitroso compounds in the gut that can damage cells lining the colon, Cancer Council Australia says. Processed meats also contain preservatives, nitrates and nitrites, which form the same harmful compounds.
• Include calcium-rich foods. Research this year from Oxford Population Health in the UK linked calcium from dairy foods and non-dairy sources to a 17 per cent lower risk of colon cancer.
• Ease off on alcohol. Two drinks or more a day increases colon cancer risk, says the World Cancer Research Fund. And don’t smoke.
• Are you 45 or over? Get screened for colon cancer, says Canfell. “Uptake of home testing via the National Bowel Cancer Screening Program is the major reason for the drop in colon cancer in the over 50s. Screening can lead to early detection of polyps before they develop into cancer and also detect any existing cancers earlier.”
• As for minimising microplastic exposure, avoiding single-use plastics, especially when heating food, and reducing packaged meals is a sensible first step, Gosavi adds. “Choosing whole foods over ultra-processed ones is likely to be beneficial, not just for reducing plastic ingestion but for broader health reasons.”

Can we reduce the impact of microplastics once they reach the gut?

“The science is in its infancy,” he says. “Some pre-clinical studies suggest that diets high in fermentable fibre, from foods such as barley, oats, legumes and nuts, for example, may help restore the mucus barrier and support protective gut bacteria. Probiotics, antioxidants, or even future pharmacological strategies could also help, but we’re not there yet.

“For now, reducing exposure and promoting overall gut health, through diet, fibre intake and microbial diversity is our best approach.”

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