The Changing Landscape of Bowel Cancer in the UK: The Role of Nutrition

Author: Holly Giles

Speakers: Dr Timothy Eden

Panellists: Prof Sumantra, Sarah Armes

Reviewers: Sarah Armes, Sarah Anderson

What is early-onset bowel cancer?

Early-onset colorectal cancer (CRC) refers to bowel cancer first presenting in adults under the age of 50. These are caused by growth abnormalities in the lining of the colon or rectum. There are differences in the clinicopathological features in younger patients.

Symptoms of bowel cancer can include unintentional weight loss, bleeding, and changes in stool habits. It is the fourth most common cancer in the UK, with almost 44,000 people being diagnosed each year.

Does bowel cancer only affect older adults?

There is a changing landscape surrounding bowel cancer, as whilst 90% of bowel cancer diagnoses are in adults aged over 50, the proportion of younger adults being diagnosed is rising annually. Cancer Research UK reports that incidents of early-onset CRC have risen by more than 50% since the early 1990s, with an increase of 3.6% each year in the last decade.

Why are the levels of early-onset bowel cancer increasing?

A common misconception is that the rise is due to the widespread application of bowel cancer screening. However, this is targeted at 50-74 year olds, meaning this is not thought to be the reason.

It is also noted that screening uptake is affected by socioeconomic factors, meaning there is a need for increased awareness and education about bowel cancer and its symptoms. Addressing socioeconomic factors is crucial for equitable outcomes for all.

Instead, it is attributed to the “birth-cohort effect”, where each generation born since 1970 has encountered unique lifestyle and environment factors such as antibiotic use in childhood, fructose intake, microplastics, sedentary lifestyles, and pollution. New research also suggests that early childhood bacterial toxin exposure, which causes a DNA mutation in the gut, increases the risk of early-onset bowel cancer.

How does diet modify bowel cancer risk?

It is known that obesity and dietary factors, such as red/processed meat and fibre intake, are significantly linked to bowel cancer risk. Numerous meta-analyses have shown that red and processed meat consumption are associated with a significant increase in colorectal cancer risk. Fortunately, the trend indicates a decrease in the consumption of red meat and processed meat among adults aged 18 to 64. However, 43% of adults still consume more than the recommended guidelines (<70 g/day).

Fibre is a critical modifiable risk factor, as it dilutes carcinogens in the gut lining and enhances short-chain fatty acid production, which has anti-inflammatory and antineoplastic properties. The recommended intake of fibre is 30g per day, but the average consumption is 18-20g per day. Only 9% of adults in the UK are estimated to reach the recommendations.

Alcohol is a group 1 carcinogen for colorectal cancer with a dose-dependent relationship.

Microbiome dysbiosis is increasingly recognised as a contributor to carcinogens. This is influenced by high alcohol consumption, low fibre intake, and consumption of red meat. Research is still ongoing in this area to understand the contribution of the microbiome to the progression of tumour growth.

How does obesity link to bowel cancer?

Obesity is directly linked to colorectal cancer risk. Men who were obese in early life had a 39% higher risk of developing colorectal cancer in adulthood. In women, this same lifestyle factor was associated with a 19% risk. This is due to multiple mechanisms, including abnormal lipid metabolism, adipokines, hormones, insulin resistance, and alterations to the gut microbiome.

Obesity also increases the risk of late diagnosis, due to a slow-growing tumour of 3-6 years, meaning that the condition is more established prior to diagnosis.

What therapeutic role can nutrition have for bowel cancer?

There is a role for prebiotics in promoting the growth of short-chain fatty acids, which enhances the barrier function and reduces inflammation within the gut. There is a need for further research to determine the therapeutic effect of pre- and probiotics at this stage.

Overall, the prevalence of early-onset colorectal cancer is on the rise. Nutrition plays a crucial role in prevention by reducing the risk of colorectal cancer: this includes minimising red meat and alcohol consumption, while boosting our fibre intake and microbiome health.

More research is needed to understand the role of pre- and probiotics from a therapeutic perspective, which may lead to the potential for personalised treatment based on microbiome profiles.