Study Identifies Possible Link Between Western Diet and Colorectal Cancer as Earlier Research Found 31% Higher Risk

By Tahani Elghazaly
Published August 15, 2026

Latest news on WhatsApp أجدد الأخبار على واتساب

A study published in Gut in July 2026 has identified a possible biological mechanism that may help explain the association between a Western-style diet and colorectal cancer. In experimental models, the diet worsened colorectal tumour development alongside increased levels of deoxycholic acid (DCA), a secondary bile acid produced by certain gut bacteria.

Researchers used pig and mouse models, human microbiome data and human colon organoids. Certain gut bacteria capable of producing secondary bile acids were associated with increased colon-cell proliferation and a greater tumour burden in the experimental models.

The human analysis also found a higher occurrence of bacterial genes involved in secondary bile-acid production in stool samples from colorectal cancer patients. However, the study does not prove that eating a Western diet directly causes colorectal cancer in humans, as the strongest causal evidence came from animal and laboratory experiments.

The findings add a possible biological explanation to earlier population research. A 2017 U.S. study followed 137,217 men and women for up to 32 years, documenting 3,260 colorectal cancer cases. People with the highest adherence to a Western dietary pattern had a 31% higher relative risk of colorectal cancer than those with the lowest adherence.

A healthier dietary pattern, by comparison, was associated with about a 14% lower overall risk. The 31% figure represents relative risk between the highest and lowest dietary-pattern groups and does not mean that 31% of people eating a Western diet will develop colorectal cancer.

The Western pattern in that research was characterized by greater consumption of red and processed meats, high-fat dairy products, refined grains and desserts, while the more prudent pattern included greater amounts of vegetables, fruit and whole grains.

The newer research suggests the relationship may involve an interaction between diet, gut bacteria and the compounds those microbes produce. The authors said the findings could support future prevention research, but they do not yet establish a specific treatment or preventive intervention for people.