Research findings from opposite sides of the world, which inform the prevention of colorectal cancer, were brought together recently in Dunedin.
Dr James Kinross, Associate Professor of surgery at Imperial College London and head of colorectal surgery at Imperial NHS trust, was a plenary speaker at the New Zealand Society for Oncology 2025 conference, held in Dunedin in October.
Kinross is a leading international expert on the microbiota that live within the gut, known as the microbiome. His group is examining how microbes contribute to colorectal cancer, and how changing the nature of the microbiome can influence treatment.
His book on the microbiome and human health, “Dark Matter”, has reached a wide audience, making complex scientific discoveries accessible and sparking public interest in the role of gut bacteria in disease.
One of the most protective elements to help prevent colorectal cancer and build a healthy microbiome is a high intake of dietary fibre.
Scientists at the University of Otago’s Edgar Diabetes and Obesity Research Centre have long studied the wide-ranging benefits of fibre in human health. Lead researchers Professor Jim Mann and Associate Professor Andrew Reynolds were excited to discuss their overlapping research interests with Kinross, which have important implications for disease prevention.
“Researchers have known about the link between the microbiome and fibre for decades. Even in the 1970s there was an awareness that the type and number of bacteria in the colon were influenced by the food we eat,” says Mann.
A metanalysis which the University of Otago group published in the top-ranking health journal The Lancet has not only confirmed some of these earlier diet-based studies, it has underpinned the recent World Health Organisation (WHO) recommendation to increase dietary fibre to levels beyond those currently consumed in New Zealand.
“This was one of the strongest nutrition recommendations ever made by the WHO. The striking dose response effects observed in our analyses indicated that the more fibre in the diet, the lower the risk of colorectal cancer and several other non-communicable diseases,” says Reynolds.
The findings led WHO to recommend an intake of at least 25g of fibre per day for everyone over 10 years of age. Currently most New Zealanders consume less than 20g of fibre a day.
New Zealand has one of the highest rates of colorectal or bowel cancer in the world, with the incidence of early onset colorectal cancer increasing over the last 5 years. Kinross and the New Zealand team hope to use their combined research efforts to help prevent bowel cancer here and around the world.
Professor Mann explains why this is an important initiative.
“In New Zealand there is, appropriately, an emphasis on the need for earlier bowel cancer screening and more equitable access to specialist care and optimal drug treatments. However there has been relatively little promotion of a cost-effective public health measure, which has the potential to reduce the risk of bowel cancer, diabetes and heart disease.”
“Taking action to increase population intakes of vegetables, fruit and wholegrains could achieve the WHO target for dietary fibre. Without greater emphasis on risk reduction it will be difficult, if not impossible, to stem the tide of colorectal cancer and the associated burden to individuals, the health service and the country more broadly,” says Mann.
Find out more about Dr Kinross' research
Bowel cancer endangers many Kiwis - how can people reduce their risk? RNZ website, 13 September, 2025