Helsinki study links plant-based swaps to lower colorectal cancer risk

A shift toward plant-based eating, even in small weekly increments, was associated with a reduced risk of colorectal cancer, according to new research from the University of Helsinki and the Finnish Institute for Health and Welfare.

• A Finnish doctoral study found that partially replacing red and processed meat with plant-based foods, especially whole grains, was associated with lower colorectal cancer risk.
• Higher whole grain intake was linked to improved markers including body mass index, waist circumference and cholesterol levels in men.
• Lifestyle factors including diet, physical activity and obesity were associated with gut microbiome changes linked to colorectal cancer risk.

Colorectal cancer remains a growing global health concern, ranking as the second most common cancer type in Finland and the third worldwide. Incidence rates have continued to rise, particularly among younger populations, prompting increased focus on preventable lifestyle factors.

The doctoral research, conducted by Rilla Tammi at the University of Helsinki’s Faculty of Medicine, examined how dietary patterns and broader lifestyle behaviors influenced colorectal cancer risk. Drawing on population data collected by the Finnish Institute for Health and Welfare, the study assessed how incremental dietary changes could shape long-term health outcomes.

Tammi’s findings suggested that even modest dietary adjustments could have meaningful effects. “The findings suggest that even small weekly dietary shifts towards more plant-based diet could reduce colorectal cancer risk at the population level,” she said.

The research focused in part on the role of whole grains, which contain all edible components of the grain, including fiber, vitamins and minerals. In contrast, refined grains lose many of these nutrients during processing, leaving primarily starch.

Higher consumption of whole grains was associated with several positive health indicators among Finnish men, including lower body mass index, reduced waist circumference and decreased serum total cholesterol levels. However, the same associations were not observed in women, highlighting potential gender differences in dietary impact that may warrant further investigation.

Tammi emphasized the broader significance of whole grain intake in public health. “The whole grain research is all the more important given that low whole grain intake has been identified as one of the key dietary factors behind years of life lost to diseases,” she said.

Beyond individual dietary components, the study examined how multiple lifestyle factors interacted. High consumption of red and processed meat, low intake of whole grains, limited physical activity and obesity were collectively associated with changes in the gut microbiome. Specifically, these factors were linked to reduced microbial diversity and a higher relative abundance of bacterial species previously connected to colorectal cancer.

Tammi argued that these microbiome characteristics could play a role in disease development, adding another layer to the relationship between diet and cancer risk. Rather than analyzing risk factors in isolation, the research applied a colorectal cancer lifestyle index to assess combined effects, offering a more comprehensive picture of real-world conditions.

This holistic approach reflected the complexity of lifestyle-driven diseases, where multiple factors often converge. By capturing these interactions, the study aimed to better understand how everyday habits influence long-term health risks.

The findings also reinforced the idea that dietary change does not need to be drastic to be effective. Replacing a portion of red or processed meat with plant-based alternatives such as whole grains, legumes or other minimally processed foods may contribute to measurable improvements over time.

Practical steps to increase whole grain intake were also highlighted. Substituting refined grain products with whole grain alternatives, choosing bread made primarily from whole grains and incorporating foods such as oatmeal porridge or barley into daily meals were identified as straightforward ways to meet recommended intake levels.

Current Finnish dietary guidelines recommend a daily intake of 90 grams of whole grains. This can be achieved through a combination of foods, including whole grain bread, porridge and grain-based side dishes.

Tammi’s doctoral thesis, titled Whole grain intake, healthy lifestyles and the gut microbiome in colorectal cancer risk, was scheduled for public defense on March 20, 2026, at the University of Helsinki’s Faculty of Medicine. The research added to a growing body of evidence linking diet, microbiome composition and chronic disease risk.

As colorectal cancer rates continue to rise globally, the study contributed further data on how relatively simple dietary adjustments may influence population health outcomes.