Five ways to cut your risk of early bowel cancer, by DR EMILY LEEMING – one of the world’s top experts investigating this alarming trend in fit young people

Why do so many young people get colon cancer? It’s a question that scientists around the world are grappling with – and that scientists includes me.

I am part of a team at King’s College London that has been awarded a £20 million grant to work with researchers from Harvard University to investigate what might be causing the extraordinary increase in cases in people under 50.

It’s not just bowel cancer. Cancer rates are rising in young people in general: Cancer Research UK reports that between 1995 and 2019, cancer rates rose by 24 per cent among 25- to 49-year-olds. That’s more than twice the increase in the over-75s, the group most at risk of developing cancer.

According to a 2015 study in the journal JAMA Surgery, the number of colorectal cancer cases among people over 50 is expected to increase by more than 140 percent by 2030. Meanwhile, the number of cases among people over 50 has leveled off worldwide.

What could be the cause of this increase?

Our international research team, funded by Cancer Research UK and Dame Deborah James’s Bowelbabe Fund, is using a range of approaches, from mouse studies and laboratory work to clinical interventions, to understand the underlying causes.

Because although 34 percent of cases of colon cancer in young people run in the family (double the number of cases of colon cancer in older people), most cases still do not have a clear genetic cause. This suggests that environment and lifestyle play a role.

But while a healthy diet and lifestyle are associated with a lower risk of bowel cancer, there are also those where the super fit, lean and healthy are also at risk of developing the disease, including Dame Deborah James, who died two years ago after being diagnosed with stage 3 bowel cancer in 2016 – at just 35 years old.

And there are important differences between colon cancer that manifests early and getting it later in life. For example, in young people, colon cancer is more likely to grow on the left side of the colon and rectum than in later life. It is also more aggressive and more likely to spread.

To try to understand what’s going on, one of the hot new areas of colon cancer research is studying how the gut microbiome – the collection of 100 trillion microorganisms that live in your small intestine – might be involved.

For example, animal studies have shown that toxins produced by ‘bad’ gut bacteria may be involved in the development of colon cancer, by causing an immune response from the cells or damaging the DNA of the cells.

Several human studies have now shown significant changes in the abundance of certain gut bacteria in people with colon cancer, including F. nucleatum, B. fragilis, and E. coli.

A study published this year in the journal Nature found that there are similar changes in the gut microbiome in colon cancer, regardless of age. Scientists have been able to accurately predict whether colon cancer is present by analyzing the composition of the gut microbiome from stool samples.

There are still many unknowns in this area of ​​research, but altering the gut microbiome is a promising potential approach to reducing the risk of colon cancer.

What can you do to reduce your risk, regardless of your age?

Stick to tap water and boiled water

A new focus in colon cancer research is microplastics. The main way microplastics enter our bodies is through what we eat and drink. They disrupt the gut and damage the mucus that lines the gut wall.

This mucus layer helps keep harmful bacteria out, but when it thins, it could potentially allow microplastics to migrate into the intestinal wall. A 2023 study in Environmental Chemistry Letters even found that colon cancer tumors contained more microplastics than the intestinal tissues of healthy people.

In addition, a new study in the journal The Proceedings of the National Academy of Sciences concluded that bottled water contains nearly ten times more microplastics than previously thought.

While you can’t avoid microplastics entirely, bottled water contains 160 times more microplastics than tap water (according to a 2023 review in the journal Science of The Total Environment). To limit your microplastic intake, drink only tap water.

Dietician and microbiome scientist Dr Emily Leeming is part of a £20 million project investigating the cause of the rising trend

Boiling water for at least five minutes can also reduce microplastic levels by up to 80 percent, as the microplastics become trapped in the limescale formed by calcium in the water. Invest in a reusable, non-plastic water bottle for you and your kids – and avoid heating food in plastic containers, as this can also help microplastics migrate into your meal. Instead, heat it in a ceramic bowl or plate.

Use processed meat only as a seasoning

Most people now know that processed meats – such as bacon, salami and ham – that have been preserved in some way, such as by curing, salting or smoking, are a recognized carcinogen that has been strongly linked to colon cancer (red meats, such as beef, pork and lamb, have also been linked, although the evidence for this is less clear).

A 2022 study in the International Journal of Epidemiology found that every 70 grams of red or processed meat eaten per day — the equivalent of two or three slices of bacon — was linked to a 32 percent increased risk of colorectal cancer.

One reason could be the way the gut microbiome breaks down iron and preservatives like nitrates and nitrites found in red and processed meat. This leads to the formation of N-nitroso compounds, potent carcinogens.

To eat less red meat, replace some of it with vegetable proteins. For example, add lentils to your bolognese sauce. When it comes to processed meat, you don’t have to cut it out completely, but try to limit your intake.

Instead, use it occasionally to flavor vegetable dishes, as vegetables contain many beneficial compounds that can neutralize some of the potential harmful substances.

Add onions to (almost) everything

There is one dietary component that is essential for good gut health: fiber. Fiber is the coarse fiber found in plant foods such as fruits, vegetables, whole grains, beans, nuts, and seeds.

Fiber keeps your intestinal lining healthy and clears out waste buildup. Every 10 grams of fiber you eat per day is linked to a 10 percent lower risk of colon cancer, according to a 2011 review of research in the BMJ.

One important type of fiber that you should try to get enough of is prebiotic fiber. When fermented by your gut bacteria, this produces short-chain fatty acids that support a healthy gut lining, reduce inflammation, and may even protect against colon cancer.

Onions, garlic, leeks, chickpeas, lentils, asparagus, Jerusalem artichokes, and chicory root are all high in prebiotic fiber. Whether you’re making an omelet, soup, sauce, or stew, try using onion and garlic as a base to boost the prebiotic fiber content.

Eat more yogurt – even the sweet kind

A 2021 study published in the journal Cell, Host & Microbe found that eating six servings of fermented foods per day increased the diversity of the gut microbiome (a sign of a healthy gut) and reduced inflammation, a risk factor for colon cancer.

Don’t think you have to eat just buckets of kimchi and sauerkraut. There are plenty of other fermented foods, including yogurt, most cheeses, kefir, tempeh, sourdough, miso, and fermented pickles.

Animal studies suggest that beneficial bacteria, like those in fermented foods, stick to the intestinal wall, preventing harmful pathogens from doing so. Even eating yogurt just once a week is linked to a 16 percent lower risk of colon cancer than never eating yogurt, according to a 2021 study in The American Journal of Clinical Nutrition.

A plain, unsweetened yogurt like Greek yogurt is a good choice, though even ultra-processed, sweetened fruit yogurts may have a similar benefit, according to a 2022 study in the BMJ.

This may seem confusing, because we know that eating a lot of ultra-processed foods is not good for your health. But not all ultra-processed foods are the same.

Preferably choose unsweetened, natural yoghurt.

Swap beer for (a little) wine

Alcohol is harmful to the gut microbiome and may be a potential factor in the development of intestinal diseases.

According to a 2003 study in the journal Gut, drinking more than 14 glasses of beer or spirits per week triples the risk of colon cancer.

Wine is a less harmful choice, possibly because it contains antioxidants such as anthocyanins and resveratrol, which can positively influence the gut microbiome and have anti-inflammatory effects.

A better choice is non-alcoholic wine, which still contains these beneficial substances but without the alcohol that irritates the intestines. Non-alcoholic or low-alcohol beers are also a good alternative.

Even people in their 20s should know the warning signs of colon cancer.

For more information, visit nhs.uk/conditions/bowelcancer/symptoms.

• DR EMILY LEEMING is a dietitian and microbiome scientist at King’s College London and author of Genius Gut: The Life-Changing Science Of Eating For Your Second Brain, out now.