January 27, 2026, 3:55 pm | Read time: 6 minutes
Diet has a major influence on the health of our intestines and, therefore, also plays a role in the development of bowel cancer. Depending on what we eat and drink, we either promote our intestinal health or increase the risk of diseases such as cancer. Researchers have now compared three different diets in terms of their role in the risk of bowel cancer. Particular focus: the low-carb diet. FITBOOK Editorial Director Melanie Hoffmann explains the details of the study.
Colorectal cancer is one of the most common forms of cancer worldwide.1 In addition to genetic factors, diet and intestinal flora play a decisive role. A growing number of studies indicate that certain strains of Escherichia coli (especially pks+ E. coli) may play a role in the development of colorectal cancer.2 These bacteria produce colibactin, a toxin that damages DNA. A research team has now investigated how different diets influence the growth of these bacteria and their carcinogenic potential. They found that a low-carb diet in particular weakens the protective mechanisms of the gut under certain circumstances and can increase the risk of bowel cancer.
Overview
What the Researchers Investigated
The researchers wanted to find out how diet, intestinal flora, and genetic susceptibility to colorectal cancer interact. The focus was on the role of pks+ E. coli, which produce colibactin and are associated with colorectal cancer.
Specifically, the study investigated how different diets affect the intestinal flora and inflammation in the intestine. The aim was to find out whether one type of diet might be more clearly associated with a risk of bowel cancer than others and, if so, which one. The scientists also wanted to test whether a possible negative effect of a diet could be reversed. In addition to a standard diet and a diet high in sugar and fat (Western diet), the low-carb diet received special attention. As this type of diet is associated with the risk of consuming too little fiber, this factor was also taken into account in the study.3
Course of the Study
In their study, the researchers experimented on mice that were genetically susceptible to bowel cancer. These were infected with various strains of bacteria, including pks+ E. coli. They were then placed on one of three diets:
- Normal standard diet (NCD)
- Low-fiber, low-carbohydrate diet (low-carb diet)
- Western diet (WSD) with high sugar and fat content
The mice were fed one of the three diets for nine weeks. The number of polyps and other markers for colorectal cancer were then analyzed. After a further seven weeks—a total of 16 weeks after the start of the study—a new examination for polyps and tumors was carried out.
The Following Were Measured:
- The number of polyps and tumors
- DNA damage caused by colibactin
- Changes in the intestinal flora
- Inflammation markers in the intestine
It was also investigated whether the negative effects could be reduced by adding fiber (inulin) or anti-inflammatory drugs (PPAR-γ agonists).
Low-Fiber, Low-Carb Diet Increased Risk of Colorectal Cancer
The results showed that of all the bacteria and diet combinations tested, only the combination of pks+ E. coli and the low-fiber, low-carb diet significantly increased the risk of colorectal cancer.4
The Findings of the Study at a Glance
Increased Tumor Formation
The mice in this group developed significantly more polyps and tumors than the other groups.
DNA Damage Due to Colibactin
The bacteria produced the genotoxic colibactin, which damaged the DNA and promoted genetic mutations.
Thinned Protective Layer in the Intestine
The low-carb diet led to a thinning of the intestinal mucosa, making it easier for colibactin to reach the intestinal cells.
Inflammation-Promoting Processes
The combination of pks+ E. coli and the low-carb diet intensified inflammatory processes, which further promoted the development of cancer.
Cellular Senescence
The affected intestinal cells showed signs of senescence (a phenomenon in which cells stop dividing)—a condition that can promote tumor growth.
Protection Through Dietary Fiber
The good news: the negative effects could be significantly attenuated by the addition of dietary fiber. Mice that also received inulin developed fewer tumors, and inflammation levels were lower.
Significance of the Study Results
The results show that diet can have a significant impact on colorectal cancer risk, especially in combination with pks+ E. coli. This is particularly worrying as E. coli can be detected in many cases of colorectal cancer, so these bacteria do not appear to be so rare in the gut.5 According to the current study, when a low-fiber diet is added to this, it increases the risk of disease by weakening the protective mechanisms of the gut and increasing inflammatory processes.
At the same time, however, there is also a promising prevention strategy: a high-fiber diet can at least partially offset the harmful effects. The researchers plan to conduct further studies to investigate which types of fiber are most effective and how these findings can be transferred to humans.
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Classification of the Study and Possible Limitations
This study provides one of the most detailed analyses to date of the interaction between diet, intestinal flora and genetic factors in the context of colorectal cancer. It shows clear mechanisms of how a low-fiber diet in combination with pks+ E. coli promotes the development of cancer.
However, There Are Some Limitations:
The study was conducted on mice—the applicability of the results to humans has yet to be confirmed.
The study focused on a specific diet combination and certain bacteria; other environmental and lifestyle factors were not taken into account. Long-term studies in humans are still needed to derive definitive recommendations.
Conclusion
This study provides new evidence that a low-fiber, low-carb diet may increase the risk of colorectal cancer—especially in combination with pks+ E. coli. The thinning of the intestinal mucosa and the increased DNA damage caused by colibactin play a key role in this.
The most important finding is that a high-fiber diet could be a simple and effective way to reduce this risk. Future research should investigate which types of fiber offer the best protection and whether these effects can also be confirmed in humans. Until then, one thing is clear: a high-fiber diet not only promotes intestinal health but could also protect against cancer.