Healthy living puts colorectal cancer at bay

As cliché as it sounds, adopting a healthy lifestyle helps prevent the development of colorectal cancer (CRC). A recent study has shown that adhering to well-balanced diet, maintaining a normal weight, staying physically active, and avoiding tobacco and alcohol all contribute to a reduction in CRC risk.

“Healthy lifestyle habits are key to primary CRC prevention,” according to the investigators, who searched the databases of PubMed and Embase through 31 March 2023 for randomized controlled trials and prospective cohort studies examining adulthood dietary patterns combined with modifiable lifestyle factors such as adiposity, smoking, alcohol consumption, physical activity, and others.

Patterns were classified by derivation methods as a priori, a posteriori, or a hybrid combining both. These were then descriptively reviewed for CRC risk or mortality, the primary outcome. Finally, the Global Cancer Update Programme Expert Committee and Expert Panel used predefined grading criteria to independently assess the evidence on the odds of causality.

The review included 33 observational studies. The panel found “strong-probable” evidence for higher levels of alignment with the a priori-derived World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) recommendations score and lower CRC risk. [Am J Clin Nutr 2025;121:986-998]

On the other hand, “limited-suggestive” evidence was concluded for the American Cancer Society (ACS) guidelines and Healthy Lifestyle Index (HLI) with lower CRC risk, primarily due to concerns about risk of bias for confounding.

Firm evidence was lacking for a posteriori-derived patterns, with only one study meeting the criteria. Additionally, “strong-probable” evidence was found for higher levels of alignment with the Empirical Lifestyle Index for Hyperinsulinemia hybrid pattern and higher CRC risk.

Analysis of cancer subsites revealed “strong-probable” evidence with lower colon cancer risk only for the WCFR/AICR recommendations. Other exposure-mortality pairs were graded “limited-no conclusion,” as was the evidence for other pattern-outcome associations.

Mechanisms

In addition, nearly a quarter of studies on a priori dietary-lifestyle patterns reported strong inverse associations with CRC risk (risk ratio [RR] range, 0.25‒0.50), while about half found moderate associations (RR range: 0.51‒0.80).

“WCRF/AICR recommendations for lower CRC risk were graded ‘strong-probable,’ whereas ACS and HLI guidelines were ‘limited—suggestive’ because of confounding concerns,” the investigators said. “These patterns emphasize healthy body weight, diet, limited red/processed meats, physical activity, and avoiding tobacco and alcohol.”

A potential mechanism driving the link between dietary-lifestyle factors and CRC risk points to insulin signalling as a “key pathway.” Specifically, hyperinsulinemia stimulate cell growth and inhibits apoptosis, thereby promoting CRC development. [Cancer Causes Control 1995;6:164-179; J Natl Cancer Inst 2004;96:546-553; Int J Cancer 2007;121:368-376; Endocrinology 2006;147:1830-1837]

Diets rich in refined carbohydrates, sugary drinks, and low in fibre could also end up impairing blood sugar control, resulting in hyperinsulinemia. [Am J Clin Nutr 2004;79:774-779; Am J Clin Nutr 2002;76:266S-273S; Nat Rev Endocrinol 2022;18:205-218]

In contrast, physical activity has been shown to prevent CRC development by improving insulin regulation, reducing inflammation/growth factors, accelerating gastrointestinal transit, or enhancing amino acid metabolism. [Nat Rev Cancer 2008;8:205-211; J Nutr 2002;132:3456S-3464S]

“These findings can inform health professionals, policymakers, researchers, and other stakeholders in promoting CRC prevention dietary-lifestyle strategies,” the researchers said.