Sarah Di Lorenzo: Bowel Cancer Month is the time to understand the connection between food and gut health

June is Bowel Cancer Awareness Month, and it is the perfect time to talk about the connection between what we eat and the health of our bowel.

Australia has one of the highest rates of bowel cancer in the world and bowel cancer is the second most common cause of cancer death in this country.

Think about this, a large proportion of cases are potentially preventable through screening and lifestyle, with diet sitting right at the centre of that prevention story.

In my clinic when it comes to gut health, most people come to see me because of immediate, day to day bowel issues such as constipation, bloating, irregular bowel habits, and the often debilitating symptoms of irritable bowel syndrome that impact quality of life.

The good news is that they are also the problems that respond most quickly and most powerfully to dietary change when that change is targeted.

Consistency is key — I see this all the time and it is very rewarding as a practitioner.

The foundation of bowel health is dietary fibre.

Most Australians are consuming only around 15–20 grams per day, compared with recommended intakes of 25 grams for women and 30 grams for men.

I really do see this as a genuine public health issue. Chronically low fibre intake drives constipation, diverticular disease, haemorrhoids, disruption of the gut microbiome, and a meaningful increase in colorectal cancer risk over time.

Observational research shows that every 10‑gram increase in daily fibre intake is associated with roughly a 10 per cent reduction in colorectal cancer risk. This is definitely worth paying attention to.

Fibre supports the health of our bowel through two main pathways. Insoluble fibre is the type found in wheat bran, vegetable skins, legumes and whole grains. This adds bulk to the stool and speeds transit through the colon.

This helps maintain regular bowel movements and reduces the contact time between potential carcinogens in the stool and the bowel wall.

Soluble fibre is found in oats, legumes, many fruits, and seeds such as chia and is fermented by gut bacteria in the colon to produce short‑chain fatty acids, particularly butyrate.

These fatty acids directly fuel the cells that line the colon, help maintain a strong gut barrier, and play a key role in reducing the low‑grade inflammation that underpins IBS symptoms and increases cancer risk.

Although there are certain foods that stand out repeatedly in both research and my clinical practice.

Kiwifruit with the skin on is one of the most evidence‑backed whole foods I use for bowel regularity.

Clinical trials show that two green kiwifruit per day can improve constipation, increasing stool frequency and improving stool consistency, with efficacy at least comparable to psyllium and often with better tolerance.

The skin contains the highest concentration of fibre and bioactive compounds, so I encourage patients to eat it where possible and suggest dicing it then adding to some yoghurt to make the skins more palatable.

Legumes including lentils, chickpeas, and cannellini beans are exceptionally rich in both soluble and insoluble fibre and are consistently associated with lower colorectal cancer risk.

Oats provide beta‑glucan, a specific soluble fibre with prebiotic properties that supports the growth of beneficial gut bacteria.

Fermented foods also have an important role. Yoghurt, kefir, sauerkraut, kombucha, kimchi and miso deliver live microbes and metabolites that help support a more diverse and resilient gut microbiome, which in turn benefits bowel motility and gut immune balance.

Leafy greens and cruciferous vegetables such as broccoli, kale, spinach, cauliflower all supply insoluble fibre, folate, and phytochemicals such as indole‑3‑carbinol, which supports healthy oestrogen metabolism and may contribute to lower colorectal cancer risk.

None of this works well, however, without adequate hydration. Fibre without sufficient fluid can worsen constipation.

As a general guide, I recommend around 30 ml of water per kilogram of body weight per day, adjusted for individual medical needs.

At the other end of the spectrum are the foods that consistently harm bowel health.

Ultra‑processed foods are almost always low in fibre, high in refined starches and unhealthy fats, and packed with additives that can disrupt the gut microbiome.

High intakes are increasingly linked with higher incidence of colorectal cancer risk.

Processed red meats such as bacon, sausages, and deli meats are now classified as Group 1 carcinogens for colorectal cancer.

Alcohol directly irritates and damages the gut lining, disrupts the microbiome, and independently increases colorectal cancer risk.

Refined white carbohydrate products such as white bread, white pasta, white rice all have had most of their fibre removed and drive the rapid blood sugar and insulin spikes that contribute to inflammation throughout the gut.

One in five Australians are affected by IBS and it is frequently misunderstood and very frustrating for those who have it.

The most evidence‑based dietary approach we have is the low FODMAP diet which is a structured, short‑term elimination of specific fermentable carbohydrates that trigger bloating, pain, diarrhoea, and constipation in sensitive individuals.

It is vital to understand that low FODMAP is not designed as a lifelong way of eating.

What concerns me is many of the foods restricted on the low FODMAP diet initially include onions, garlic, wheat, and legumes and are among the most protective foods we have for long‑term bowel and metabolic health.

The goal is always to slowly reintroduce as many of these foods as the individual can tolerate and many don’t do this step.

It is so important to remember that the bowel is not an isolated organ to be managed separately from the rest of the body.

It is the centre of immune function, metabolic health, hormonal balance, and long‑term cancer risk.

When we feed it well with fibre, plant diversity, fermented foods, and adequate water we do far more than achieve regular bowel movements; we lay the groundwork for long‑term health across multiple systems.