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The study was published online in Nature Microbiology on March 3, 2025, and conducted by Alberto Martin, Department of Immunology, University of Toronto, Toronto, Ontario, Canada, and colleagues.

Using a mouse model, scientists examined the effects of three different diets—low-carb, normal, and Westernized—while exposing the mice to specific bacterial strains, including Bacteroides fragilis, Helicobacter hepaticus, and colibactin-producing E. coli (pks+ E. coli). Their findings highlighted a concerning link between low-carb, low-fiber diets and increased polyp formation in the presence of pks+ E. coli, which may raise the risk of colorectal cancer.

The study revealed that mice on a low-carb, low-fiber diet colonized with pks+ E. coli developed more polyps and tumors than those on other diets. This is significant, as E. coli is found in approximately 60% of colorectal cancer cases. The low-carb diet also thinned the protective mucus layer in the colon, making it easier for colibactin, a genotoxin produced by E. coli, to damage DNA. The affected mice showed DNA damage, increased inflammation, and cellular senescence—key factors contributing to cancer development.

Interestingly, when fiber was introduced into the diet, tumor formation was reduced, and inflammation levels improved. This suggests that dietary fiber protects against the harmful effects of pks+ E. coli, possibly by maintaining gut health and reducing inflammation.

The study emphasizes the importance of diet in cancer prevention, particularly the potential dangers of low-carb diets that lack fiber. While low-carb diets, such as keto, have gained popularity for weight management, their long-term health effects remain a topic of concern. The researchers now aim to explore which types of dietary fiber offer the most protective benefits and whether similar effects are observed in humans.

These findings highlight the complex relationship between diet, gut bacteria, and cancer risk, reinforcing the importance of a balanced diet rich in fiber to support gut health and reduce the likelihood of colorectal cancer development.

“The pks+ E. coli led to more polyp growth in mice with impaired DNA repair by triggering harmful cellular changes linked to aging. Additionally, inflammation further increased its cancer-promoting effects in these mice. These findings suggest that diet and genetics play a role in how this common bacterium contributes to cancer development,” the researchers concluded.

Reference:

Thakur, B. K., Malaise, Y., Choudhury, S. R., Neustaeter, A., Turpin, W., Streutker, C., Copeland, J., Wong, E. O., Navarre, W. W., Guttman, D. S., Jobin, C., Croitoru, K., & Martin, A. (2025). Dietary fibre counters the oncogenic potential of colibactin-producing Escherichia coli in colorectal cancer. Nature Microbiology, 1-16. https://doi.org/10.1038/s41564-025-01938-4

The incidence of ischemic stroke in the young is increasing and driven by cryptogenic strokes. Smoking is a well-documented risk factor with a high prevalence in young ischemic strokes. We sought to determine the association between smoking and young cryptogenic ischemic stroke (CIS) in a large multicenter case-control study. In the Searching for Explanations for Cryptogenic Stroke in the Young: Revealing the Etiology, Triggers, and Outcome (SECRETO; NCT01934725) study, patients with CIS aged 18–49 years were prospectively recruited within 2 weeks of symptom onset from 19 European stroke centers. One sex-matched and age-matched (±5 years) stroke-free control was recruited per patient. Data on tobacco use and intensity of use, socioeconomic status, and comorbidities were collected using a standardized questionnaire. Conditional logistic regression with adjustment for low education status and vascular risk factors was used to assess the association between smoking and intensity of smoking and CIS. Results: A total of 546 young patients with CIS (47.3% female) and their matched controls were included in the analysis. Univariate comparison between patients and controls showed a significant difference in low education status (55.6% vs 35.2%, p ≤ 0.001), hypertension (34.7% vs 26.8%, p ≤ 0.005), obesity (59.3% vs 44.4%, p ≤ 0.001), physical inactivity (29.4% vs 23.6%, p ≤ 0.02), smoking (32.8% vs 14.8%, p ≤ 0.001), and heavy alcohol use (13.7% vs 6.7%, p ≤ 0.001). Conditional logistic regression after adjustment showed an association between smoking and young CIS in the whole cohort with an odds ratio of 2.39 (95% CI 1.65–3.47), in men with 3.34 (1.91–5.84), and in all age groups—highest in the 45–49-year age group—with 3.77 (1.74–8.17). Analysis of smoking intensity by pack year showed the strongest association in the group with >20 pack years with an odds ratio of 4.30 (2.10–8.81), particularly in men (6.97 (2.58–18.82)) and the 45–49-year age group (4.91 (1.74–13.85)). Both smoking and high-intensity smoking were associated with CIS in the young, particularly in men and the 45–49-year age group.

Reference:

Ferdinand P, Bajpai R, Von Sarnowski B, et al. Association of Smoking and Young Cryptogenic Ischemic Stroke: A Case-Control Study. Neurology Open Access. 2025;1(1). doi:10.1212/WN9.0000000000000003.

Keywords:

Smoking, double, Risk, Cryptogenic, Ischemic, Stroke, suggests, research, Ferdinand P, Bajpai R, Von Sarnowski B